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  • 1.
    Albertin, S.
    et al.
    Lund Univ, Div Synchrotron Radiat Res, Box 118, S-22100 Lund, Sweden..
    Gustafson, J.
    Lund Univ, Div Synchrotron Radiat Res, Box 118, S-22100 Lund, Sweden..
    Zhou, J.
    Lund Univ, Div Combust Phys, SE-22100 Lund, Sweden..
    Pfaff, S.
    Lund Univ, Div Combust Phys, SE-22100 Lund, Sweden..
    Shipilin, M.
    Stockholm Univ, Div Phys Chem, SE-10691 Stockholm, Sweden..
    Blomberg, S.
    Lund Univ, Dept Chem Engn, SE-22100 Lund, Sweden..
    Merte, Lindsay R.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Gutowski, O.
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Dippel, A-C
    Deutsch Elektronen Synchrotron DESY, D-22607 Hamburg, Germany..
    Zetterberg, J.
    Lund Univ, Div Combust Phys, SE-22100 Lund, Sweden..
    Lundgren, E.
    Lund Univ, Div Synchrotron Radiat Res, Box 118, S-22100 Lund, Sweden..
    Hejral, U.
    Lund Univ, Div Synchrotron Radiat Res, Box 118, S-22100 Lund, Sweden..
    Surface optical reflectance combined with x-ray techniques during gas-surface interactions2020In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 53, no 22, article id 224001Article in journal (Refereed)
    Abstract [en]

    High energy surface x-ray diffraction (HESXRD), x-ray reflectivity (XRR), mass spectrometry (MS) and surface optical reflectance (SOR) have been combined to simultaneously obtain sub-second information on the surface structure and morphology from a Pd(100) model catalyst during in situ oxidation at elevated temperatures and pressures resulting in Pd bulk oxide formation. The results show a strong correlation between the HESXRD and SOR signal intensities during the experiment, enabling phase determination and a time-resolved thickness estimation of the oxide by HESXRD, complemented by XRR measurements. The experiments show a remarkable sensitivity of the SOR to changes in the surface phase and morphology, in particular to the initial stages of oxidation/reduction. The data imply that SOR can detect the formation of an ultrathin PdO surface oxide layer of only 2-3 angstrom thickness.

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  • 2.
    Albertin, Stefano
    et al.
    Division of Synchrotron Radiation Research, Lund University, SE-22100 Lund, Sweden.
    Merte, Lindsay R.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Lundgren, Edvin
    Division of Synchrotron Radiation Research, Lund University, SE-22100 Lund, Sweden.
    Martin, Rachel
    Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, United States.
    Weaver, Jason F.
    Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, United States.
    Dippel, Ann-Christin
    Deutsches Elektronen-Synchrotron (DESY), 22603 Hamburg, Germany.
    Gutowski, Olof
    Deutsches Elektronen-Synchrotron (DESY), 22603 Hamburg, Germany.
    Hejral, Uta
    Division of Synchrotron Radiation Research, Lund University, SE-22100 Lund, Sweden.
    Oxidation and Reduction of Ir(100) Studied by High-Energy Surface X-ray Diffraction2022In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 11, p. 5244-5255Article in journal (Refereed)
    Abstract [en]

    The oxidation and reduction of an Ir(100) surface using 2.5, 5, and 10 mbar O2 partial pressure and a sample temperature of 775 K have been studied by using high-energy surface X-ray diffraction (HESXRD) which allowed to record large volumes of reciprocal space in short time periods. The complex 3D diffraction patterns could be disentangled in a stepwise procedure. For the 2.5mbar experiment the measurements indicate the formation of an Ir(100)-O c(2 × 2) oxygen superstructure along with the onset of epitaxial IrO2(110) bulk oxide formation. For the 5 and 10 mbar O2 partial pressures the formation of additional IrO2 bulk oxide epitaxies with (100) and (101) orientations as well as of polycrystalline IrO2 was observed. Upon CO reduction, we found the IrO2 islands to be reduced into epitaxial and metallic Ir(111) and (221) oriented islands.

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  • 3.
    Argatov, Ivan
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Institut für Mechanik, Technische Universität Berlin, 10623 Berlin, Germany.
    Engblom, Johan
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Modeling of composite sorption isotherm for stratum corneum2022In: Biochimica et Biophysica Acta - Biomembranes, ISSN 0005-2736, E-ISSN 1879-2642, Vol. 1864, no 7, p. 1-8, article id 183910Article in journal (Refereed)
    Abstract [en]

    Equilibrium water sorption in stratum corneum (SC) is considered by treating it as a biocomposite with two main phases, namely, corneocytes and lipids. To validate the rule of mixtures for the individual phase sorption isotherms, a new flexible fitting model is introduced by accounting for characteristic features observed in the variations of the thermodynamic correction factors corresponding to the individual sorption isotherms. The comparison of the model fitting performance with that of the five-parameter Park's model shows a remarkably good ability to fit experimental data for different types of sorption isotherms. The effect of the lipids content on the variance of the composite sorption isotherm of stratum corneum is highlighted. The sensitivity analysis reveals that for the typical water content 20-30 wt%, which corresponds to the SC in a stable condition, the sensitivity of the composite sorption isotherm to the variation of the lipids content on dry basis is predominantly positive and sufficiently small. The good agreement observed between the experimental sorption isotherm for SC and the composite isotherm, which is based on the rule of mixtures for the individual phase sorption isotherms, yields a plausible conclusion (hypothesis) that the corneocytes-lipids mechanical interaction during unconstrained swelling of the SC membrane in the in vitro laboratory experiment is negligible.

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  • 4.
    Argatov, Ivan
    et al.
    Malmö University, Biofilms Research Center for Biointerfaces. Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Chongqing University, China.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    An empirical model for sorption by glassy polymers: An assessment of thermodynamic parameters2021In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 99Article in journal (Refereed)
    Abstract [en]

    A new fitting model for sorption by glassy polymers is suggested based on the Flory–Huggins (FH) equation with a composite formula for the FH interaction parameter, χ, which is applicable if sorption experimental data shows a single-maximum variation of the FH parameter. Namely, a power-like and a linear approximation is assumed for χ(φ1), as a function of solvent volume fraction φ1, before and after the point of its maximum. After determining the maximum point from a direct inspection of the sorption data, the three fitting parameters are evaluated by solving two independent least-square minimization problems. Several sorption studies of biopolymers taken from the literature show that the endset of the glass transition region is correlated with the position of the maximum of the FH interaction parameter. Based on this hypothesis and the Vrentas–Vrentas model for sorption of glassy polymers, a theoretical framework for the glass transition analysis is developed. In particular, the solvent-induced glass transition temperature variation can be estimated from the sorption isotherm as a function of the solvent content corresponding to temperatures above the temperature of sorption.

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  • 5.
    Argatov, Ivan
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Tech Univ Berlin, Inst Mech, D-10623 Berlin, Germany..
    Roosen-Runge, Felix
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Dynamics of post-occlusion water diffusion in stratum corneum2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, no 1, article id 17957Article in journal (Refereed)
    Abstract [en]

    Diffusion of water through membranes presents a considerable challenge, as the diffusivity often depends on the local concentration of water. One particular example with strong biological relevance is the stratum corneum (SC) as the primary permeability barrier for the skin. A simple alternative for the constant diffusivity model is provided by the Fujita's two-parameter rational approximation, which captures the experimentally observed fact that the SC diffusion constant for water increases with increasing the water concentration. Based on Fick's law of diffusion, a one-dimensional concentration-dependent diffusion model is developed and applied for the analysis of both the steady-state transepidermal water loss (TEWL) and the non-steady-state so-called skin surface water loss (SSWL) occurred after removal of an occlusion patch from the SC surface. It is shown that some of the age-related changes in the SSWL can be qualitatively explained by the variation of the dimensionless Fujita concentration-dependence parameter.

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  • 6.
    Beck, Christian
    et al.
    Univ Tubingen, Inst Angew Phys, Morgenstelle 10, D-72076 Tubingen, Germany.;Inst Max von Laue Paul Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Grimaldo, Marco
    Inst Max von Laue Paul Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Braun, Michal K.
    Univ Tubingen, Inst Angew Phys, Morgenstelle 10, D-72076 Tubingen, Germany..
    Buhl, Lena
    Univ Tubingen, Inst Angew Phys, Morgenstelle 10, D-72076 Tubingen, Germany..
    Matsarskaia, Olga
    Inst Max von Laue Paul Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Jalarvo, Niina H.
    Forschungszentrum Julich, Julich Ctr Neutron Sci JCNS, D-52425 Julich, Germany.;Oak Ridge Natl Lab, Chem & Engn Mat Div, Neutron Sci Directorate, POB 2008, Oak Ridge, TN 37831 USA.;Oak Ridge Natl Lab, JCNS Outstn Spallat Neutron Source SNS, POB 2008, Oak Ridge, TN 37831 USA..
    Zhang, Fajun
    Univ Tubingen, Inst Angew Phys, Morgenstelle 10, D-72076 Tubingen, Germany..
    Roosen-Runge, Felix
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Lund Univ, Div Phys Chem, Nat Vetarvagen 14, S-22100 Lund, Sweden..
    Schreiber, Frank
    Univ Tubingen, Inst Angew Phys, Morgenstelle 10, D-72076 Tubingen, Germany..
    Seydel, Tilo
    Inst Max von Laue Paul Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Temperature and salt controlled tuning of protein clusters2021In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, no 37, p. 8506-8516Article in journal (Refereed)
    Abstract [en]

    The formation of molecular assemblies in protein solutions is of strong interest both from a fundamental viewpoint and for biomedical applications. While ordered and desired protein assemblies are indispensable for some biological functions, undesired protein condensation can induce serious diseases. As a common cofactor, the presence of salt ions is essential for some biological processes involving proteins, and in aqueous suspensions of proteins can also give rise to complex phase diagrams including homogeneous solutions, large aggregates, and dissolution regimes. Here, we systematically study the cluster formation approaching the phase separation in aqueous solutions of the globular protein BSA as a function of temperature (T), the protein concentration (c(p)) and the concentrations of the trivalent salts YCl3 and LaCl3 (c(s)). As an important complement to structural, i.e. time-averaged, techniques we employ a dynamical technique that can detect clusters even when they are transient on the order of a few nanoseconds. By employing incoherent neutron spectroscopy, we unambiguously determine the short-time self-diffusion of the protein clusters depending on c(p), c(s) and T. We determine the cluster size in terms of effective hydrodynamic radii as manifested by the cluster center-of-mass diffusion coefficients D. For both salts, we find a simple functional form D(c(p), c(s), T) in the parameter range explored. The calculated inter-particle attraction strength, determined from the microscopic and short-time diffusive properties of the samples, increases with salt concentration and temperature in the regime investigated and can be linked to the macroscopic behavior of the samples.

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  • 7.
    Beck, Christian
    et al.
    Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany; Institut Max von Laue Paul Langevin (ILL), CS 20156, F-38042 Grenoble Cedex 9, France..
    Pounot, Kevin
    Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany; Institut Max von Laue Paul Langevin (ILL), CS 20156, F-38042 Grenoble Cedex 9, France..
    Mosca, Ilaria
    Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany; Institut Max von Laue Paul Langevin (ILL), CS 20156, F-38042 Grenoble Cedex 9, France..
    H Jalarvo, Niina
    Jülich Centre for Neutron Science (JCNS), Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany; Chemical and Engineering Materials Division, Neutron Sciences Directorate, and JCNS Outstation at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, USA.
    Roosen-Runge, Felix
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Schreiber, Frank
    Institut für Angewandte Physik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Seydel, Tilo
    Institut Max von Laue Paul Langevin (ILL), CS 20156, F-38042 Grenoble Cedex 9, France.
    Notes on Fitting and Analysis Frameworks for QENS Spectra of (Soft) Colloid Suspensions2022In: EPJ Web of Conferences, E-ISSN 2100-014X, Vol. 272, p. 01004-01004Article in journal (Refereed)
    Abstract [en]

    With continuously improving signal-to-noise ratios, a statistically sound analysis of quasi-elasticneutron scattering (QENS) spectra requires to fit increasingly complex models which poses several challenges.Simultaneous fits of the spectra for all recorded values of the momentum transfer become a standard approach.Spectrometers at spallation sources can have a complicated non-Gaussian resolution function which has to bedescribed most accurately. At the same time, to speed up the fitting, an analytical convolution with this resolutionfunction is of interest. Here, we discuss basic concepts to efficient approaches for fits of QENS spectra basedon standard MATLAB and Python fit algorithms. We illustrate the fits with example data from IN16B, BASIS,and BATS.

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  • 8.
    Blomqvist Rippner, B
    et al.
    Institute for Surface Chemistry, Box 5607, SE-114 86 Stockholm, Sweden.
    Benjamins, J-W
    Department of Chemistry, Surface Chemistry, Royal Institute of Technology, Drottning Kristinas väg 51,SE-100 44 Stockholm, Sweden.
    Nylander, Tommy
    Physical Chemistry 1, Lund University, Box 124,SE-221 00 Lund, Sweden.
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Ellipsometric characterization of ethylene oxide-butylene oxide diblock copolymer adsorption at the air-water interface2005In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 21, no 11, p. 5061-5068Article in journal (Refereed)
    Abstract [en]

    Ellipsometry was used to determine the adsorbed layer thickness (d) and the surface excess (adsorbed amount, Γ) of a nonionic diblock copolymer, E106B16, of poly(ethylene oxide) (E) and poly(butylene oxide) (B) at the air−water interface. The results were obtained (i) by the conventional ellipsometric evaluation procedure using the change of both ellipsometric angles Ψ and Δ and (ii) by using the change of Δ only and assuming values of the layer thickness. It was demonstrated that the calculated surface excesses from the different methods were in close agreement, independent of the evaluation procedure, with a plateau adsorption of about 2.5 mg/m2 (400 Å2/molecule). Furthermore, the amount of E106B16 adsorbed at the air−water interface was found to be almost identical to that adsorbed from aqueous solution onto a hydrophobic solid surface. In addition, the possibility to use combined measurements with H2O or D2O as substrates to calculate values of d and Γ was investigated and discussed. We also briefly discuss within which limits the Gibbs equation can be used to determine the surface excess of polydisperse block copolymers.

  • 9.
    Bogdanova, Ekaterina
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. NextBioForm Competence Centre, Stockholm, Sweden.
    Fureby, Anna Millqvist
    RISE Research Institutes of Sweden, Stockholm, Sweden; NextBioForm Competence Centre, Stockholm, Sweden.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. NextBioForm Competence Centre, Stockholm, Sweden.
    Influence of cooling rate on ice crystallization and melting in sucrose-water system2022In: Journal of Pharmaceutical Sciences, ISSN 0022-3549, E-ISSN 1520-6017, Vol. 111, no 7, p. 2030-2037, article id S0022-3549(22)00035-1Article in journal (Refereed)
    Abstract [en]

    The ice crystallization and melting in systems where the equilibrium state is difficult to reach is one of the growing areas in pharmaceutical freeze-drying research. The quality of the final freeze-dried product depends on the parameters of the cooling step, which affect the ice nucleation and growth. In this paper, we present a DSC study of ice crystallization and melting in a sucrose-water system. Using two different types of thermal cycles, we examine the influence of cooling and heating rates on the thermal behavior of sucrose-water solutions with water contents between 50 and 100 wt%.

    The DSC results show that low cooling rates provide crystallization at higher temperatures and lead to lower amount of nonfreezing water. Consequently, the glass transition and ice melting properties observed upon heating depend on the cooling conditions in the preceding step. Based on the experimental results, we investigate the reasons for the existence of the two steps on DSC heating curves in sucrose-water systems: the glass transition step and the onset of ice melting. We show that diffusion of water can be the limiting factor for ice growth and melting in the sucrose-water system when the amorphous phase is in a liquid state. In particular, when the diffusion coefficient drops below 10−14 m2/sec, the ice crystals growth or melting becomes strongly suppressed even above the glass transition temperature. Understanding the diffusion limitations in the sucrose-water system can be used for the optimization of the freeze-drying protocols for proteins and probiotics.

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  • 10.
    Bogdanova, Ekaterina
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Lages, Sebastian
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. MAX IV Laboratory, Lund University, Lund SE-22484, Sweden.
    Phan-Xuan, Tuan
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. MAX IV Laboratory, Lund University, Lund SE-22484, Sweden.
    Kamal, Md Arif
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Division of Physical Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden.
    Terry, Ann
    MAX IV Laboratory, Lund University, Lund SE-22484, Sweden.
    Millqvist Fureby, Anna
    RISE Research Institutes of Sweden, Stockholm SE-114 86, Sweden.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Lysozyme-Sucrose Interactions in the Solid State: Glass Transition, Denaturation, and the Effect of Residual Water.2023In: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 20, no 9, p. 4664-4675Article in journal (Refereed)
    Abstract [en]

    The freeze-drying of proteins, along with excipients, offers a solution for increasing the shelf-life of protein pharmaceuticals. Using differential scanning calorimetry, thermogravimetric analysis, sorption calorimetry, and synchrotron small-angle X-ray scattering (SAXS), we have characterized the properties at low (re)hydration levels of the protein lysozyme, which was freeze-dried together with the excipient sucrose. We observe that the residual moisture content in these samples increases with the addition of lysozyme. This results from an increase in equilibrium water content with lysozyme concentration at constant water activity. Furthermore, we also observed an increase in the glass transition temperature (Tg) of the mixtures with increasing lysozyme concentration. Analysis of the heat capacity step of the mixtures indicates that lysozyme does not participate in the glass transition of the sucrose matrix; as a result, the observed increase in the Tg of the mixtures is the consequence of the confinement of the amorphous sucrose domains in the interstitial space between the lysozyme molecules. Sorption calorimetry experiments demonstrate that the hydration behavior of this formulation is similar to that of the pure amorphous sucrose, while the presence of lysozyme only shifts the sucrose transitions. SAXS analysis of amorphous lysozyme–sucrose mixtures and unfolding of lysozyme in this environment show that prior to unfolding, the size and shape of lysozyme in a solid sucrose matrix are consistent with its native state in an aqueous solution. The results obtained from our study will provide a better understanding of the low hydration behavior of protein–excipient mixtures and support the improved formulation of biologics.

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  • 11.
    Bogdanova, Ekaterina
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Millqvist Fureby, Anna
    RISE Research Institutes of Sweden.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Hydration enthalpies of amorphous sucrose, trehalose and maltodextrins and their relationship with heat capacities2021In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, no 26, p. 14433-14448Article in journal (Refereed)
    Abstract [en]

    The mechanisms of glass transitions and the behavior of small solute molecules in a glassy matrix are some of the most important topics of modern thermodynamics. Water plays an important role in the physical and chemical stability of lyophilized biologics formulations, in which glassy carbohydrates act as cryoprotectants and stabilizers. In this study, sorption calorimetry was used for simultaneous measurements of water activity and the enthalpy of water sorption by amorphous sucrose, trehalose and maltodextrins. Moreover, the heat capacity of these carbohydrates in mixtures with water was measured by DSC in a broad range of water contents. The hydration enthalpies of glassy sucrose, trehalose and maltodextrins are exothermic, and the enthalpy change of water-induced isothermal glass transitions is higher for small molecules. The partial molar enthalpy of mixing of water in slow experiments is about -18 kJ mol-1, but less exothermic in the case of small molecules at fast hydration scan rates. By measuring the heat capacities of disaccharides and maltodextrins as a function of water content, we separated the contributions of carbohydrates and water to the total heat capacities of the mixtures. The combination of these data allowed testing of thermodynamic models describing the hydration-induced glass transitions. The heat capacity changes calculated by the fitting of the hydration enthalpy data for disaccharides are in good agreement with the heat capacity data obtained by DSC, while for maltodextrins, the effect of sub-Tg transitions should be taken into account. Combining the data obtained by different techniques, we found a distinct difference in the behavior of water in glassy polymers compared to that in glassy disaccharides. By understanding the behavior of water in glassy carbohydrates, these results can be used to improve the design of freeze-dried formulations of proteins and probiotics.

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  • 12.
    Boyd, Hannah
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Gonzalez-Martinez, Juan F
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Welbourn, Rebecca J L
    Rutherford Appleton Laboratory, UK.
    Ma, Kun
    Rutherford Appleton Laboratory, UK.
    Li, Peixun
    Rutherford Appleton Laboratory, UK.
    Gutfreund, Philipp
    Institut Laue Langevin, France.
    Klechikov, Alexey
    Institut Laue Langevin, France; Uppsala University.
    Arnebrant, Thomas
    Malmö University, Biofilms Research Center for Biointerfaces. Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    Barker, Robert
    University of Kent, UK.
    Sotres, Javier
    Malmö University, Biofilms Research Center for Biointerfaces. Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    Effect of nonionic and amphoteric surfactants on salivary pellicles reconstituted in vitro2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 12913Article in journal (Refereed)
    Abstract [en]

    Surfactants are important components of oral care products. Sodium dodecyl sulfate (SDS) is the most common because of its foaming properties, taste and low cost. However, the use of ionic surfactants, especially SDS, is related to several oral mucosa conditions. Thus, there is a high interest in using non-ionic and amphoteric surfactants as they are less irritant. To better understand the performance of these surfactants in oral care products, we investigated their interaction with salivary pellicles i.e., the proteinaceous films that cover surfaces exposed to saliva. Specifically, we focused on pentaethylene glycol monododecyl ether (C12E5) and cocamidopropyl betaine (CAPB) as model nonionic and amphoteric surfactants respectively, and investigated their interaction with reconstituted salivary pellicles with various surface techniques: Quartz Crystal Microbalance with Dissipation, Ellipsometry, Force Spectroscopy and Neutron Reflectometry. Both C12E5 and CAPB were gentler on pellicles than SDS, removing a lower amount. However, their interaction with pellicles differed. Our work indicates that CAPB would mainly interact with the mucin components of pellicles, leading to collapse and dehydration. In contrast, exposure to C12E5 had a minimal effect on the pellicles, mainly resulting in the replacement/solubilisation of some of the components anchoring pellicles to their substrate.

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  • 13.
    Cao, Cheng
    et al.
    Centre for Advanced Macromolecular Design, School of Chemistry, The University of New South Wales, Sydney, 2052, Australia.
    Zhang, Lin
    Centre for Advanced Macromolecular Design, School of Chemistry, The University of New South Wales, Sydney, 2052, Australia.
    Kent, Ben
    Centre for Advanced Macromolecular Design, School of Chemistry, The University of New South Wales, Sydney, 2052, Australia.
    Wong, Sandy
    Centre for Advanced Macromolecular Design, School of Chemistry, The University of New South Wales, Sydney, 2052, Australia.
    Garvey, Christopher J.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Australian Centre for Neutron Scattering, Australia Nuclear Science and Technology Organisation, Lucas Heights, 2234, Australia; Lund Institute for Advanced Neutron and X-ray Science, Lund, 22100, Sweden.
    Stenzel, Martina H.
    Centre for Advanced Macromolecular Design, School of Chemistry, The University of New South Wales, Sydney, 2052, Australia.
    The Protein Corona Leads to Deformation of Spherical Micelles2021In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 60, no 18, p. 10342-10349Article in journal (Refereed)
    Abstract [en]

    The formation of a non-specific protein corona around nanoparticles (NPs) has been identified as one of the culprits for failed nanomedicine. The amount and type of adsorbed protein from the blood plasma are known to determine the fate of NPs and the accessibility of targeting ligands. Herein, we show that the adsorbed protein may not only enlarge the NPs and change their surface properties but also, in the case of soft NPs such as polymer micelles, lead to deformation. Poly(1-O-methacryloyl -beta-D-fructopyranose)-b-poly(methylmethacrylate) (P(1-O-MAFru)-b-PMMA) block co-polymers were self-assembled into NPs with a spherical core-shell morphology as determined by small angle neutron scattering (SANS). Upon incubation with albumin, TEM, SANS, and small angle X-ray scattering (SAXS) revealed the adsorption of albumin and deformation of the NPs with a spheroid geometry. Removal of the protein led to the reversal of the morphology back to the spherical core-shell structure. Structural studies and cell studies of uptake of the NPs imply that the observed deformation may influence blood circulation time and cell uptake.

  • 14.
    Chushkin, Yuriy
    et al.
    ESRF, The European Synchrotron, 71 Avenue des Martyrs, CS40220, 38043 Grenoble Cedex 9, France.
    Gulotta, Alessandro
    Division of Physical Chemistry, Lund University, Naturvetarvägen 14, 22100 Lund, Sweden.
    Roosen-Runge, Felix
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Division of Physical Chemistry, Lund University, Naturvetarvägen 14, 22100 Lund, Sweden.
    Pal, Antara
    Division of Physical Chemistry, Lund University, Naturvetarvägen 14, 22100 Lund, Sweden.
    Stradner, Anna
    Division of Physical Chemistry, Lund University, Naturvetarvägen 14, 22100 Lund, Sweden; Lund Institute of advanced Neutron and X-ray Science LINXS, Lund University, Lund, Sweden.
    Schurtenberger, Peter
    Division of Physical Chemistry, Lund University, Naturvetarvägen 14, 22100 Lund, Sweden; Lund Institute of advanced Neutron and X-ray Science LINXS, Lund University, Lund, Sweden.
    Probing Cage Relaxation in Concentrated Protein Solutions by X-Ray Photon Correlation Spectroscopy2022In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 129, no 23, article id 238001Article in journal (Refereed)
    Abstract [en]

    Diffusion of proteins on length scales of their size is crucial for understanding the machinery of living cells. X-ray photon correlation spectroscopy (XPCS) is currently the only way to access long-time collective diffusion on these length scales, but radiation damage so far limits the use in biological systems. We apply a new approach to use XPCS to measure cage relaxation in crowded α-crystallin solutions. This allows us to correct for radiation effects, obtain missing information on long time diffusion, and support the fundamental analogy between protein and colloid dynamical arrest.

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  • 15.
    Clifton, Luke A
    et al.
    ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 OQX, United Kingdom.
    Campbell, Richard A
    Division of Pharmacy and Optometry, University of Manchester, Manchester M13 9PT, United Kingdom.
    Sebastiani, Federica
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Campos-Terán, José
    Departamento de Procesos y Tecnología, Universidad Autónoma Metropolitana, Unidad Cuajimalpa, Av. Vasco de Quiroga 4871, Col. Santa Fe, Delegación Cuajimalpa de Morelos, 05348, Mexico; Lund Institute of advanced Neutron and X-ray Science, Lund University, Scheelevägen 19, 223 70 Lund, Sweden.
    Gonzalez-Martinez, Juan F
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Björklund, Sebastian
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Sotres, Javier
    Malmö University, Biofilms Research Center for Biointerfaces. Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    Cárdenas, Marité
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Design and use of model membranes to study biomolecular interactions using complementary surface-sensitive techniques.2020In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 277, article id 102118Article in journal (Refereed)
    Abstract [en]

    Cellular membranes are complex structures and simplified analogues in the form of model membranes or biomembranes are used as platforms to understand fundamental properties of the membrane itself as well as interactions with various biomolecules such as drugs, peptides and proteins. Model membranes at the air-liquid and solid-liquid interfaces can be studied using a range of complementary surface-sensitive techniques to give a detailed picture of both the structure and physicochemical properties of the membrane and its resulting interactions. In this review, we will present the main planar model membranes used in the field to date with a focus on monolayers at the air-liquid interface, supported lipid bilayers at the solid-liquid interface and advanced membrane models such as tethered and floating membranes. We will then briefly present the principles as well as the main type of information on molecular interactions at model membranes accessible using a Langmuir trough, quartz crystal microbalance with dissipation monitoring, ellipsometry, atomic force microscopy, Brewster angle microscopy, Infrared spectroscopy, and neutron and X-ray reflectometry. A consistent example for following biomolecular interactions at model membranes is used across many of the techniques in terms of the well-studied antimicrobial peptide Melittin. The overall objective is to establish an understanding of the information accessible from each technique, their respective advantages and limitations, and their complementarity.

  • 16.
    Conn, Charlotte E
    et al.
    RMIT University, Australia.
    de Campo, Liliana
    Australian Nuclear Science and Technology Organisation.
    Whitten, Andrew E
    Australian Nuclear Science and Technology Organisation.
    Garvey, Christopher J.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Australian Nuclear Science and Technology Organisation; Lund Institute for Advanced Neutron and X-Ray Science.
    Krause-Heuer, Anwen M
    Australian Nuclear Science and Technology Organisation.
    van 't Hag, Leonie
    Monash University, Monash University.
    Membrane Protein Structures in Lipid Bilayers; Small-Angle Neutron Scattering With Contrast-Matched Bicontinuous Cubic Phases2020In: Frontiers in chemistry, ISSN 2296-2646, Vol. 8, article id 619470Article in journal (Refereed)
    Abstract [en]

    . Deuterated vesicles can be used to obtain the radius of gyration of membrane proteins, but protein-protein interference effects within the vesicles severely limits this method such that the protein structure cannot be modeled. We show herein that different membrane protein conformations can be distinguished within the lipid bilayer of the bicontinuous cubic phase using contrast-matching. Time-resolved studies performed using SANS illustrate the complex phase behavior in lyotropic liquid crystalline systems and emphasize the importance of this development. We believe that studying membrane protein structures and phase behavior in contrast-matched lipid bilayers will advance both biological and pharmaceutical applications of membrane-associated proteins, biosensors and food science.

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  • 17.
    Cárdenas, Marité
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Schillén, Karin
    Alfredsson, Viveka
    Duan, Rui-DOng
    Nyberg, Lena
    Solubilization of sphingomyelin vesicles by addition of a bile salt2008In: Chemistry and Physics of Lipids, ISSN 0009-3084, E-ISSN 1873-2941, Vol. 151, no 1, p. 10-17Article in journal (Refereed)
    Abstract [en]

    The interactions of the bile salt sodium taurocholate (TC) in 50 mM Trizma–HCl buffer and 150 mM NaCl (pH 9) at 37 °C with membranes composed of sphingomyelin (SM) were studied by dynamic light scattering, cryogenic transmission electron microscopy (cryo-TEM) and turbidity measurements. Small unilamellar SM vesicles were prepared by extrusion. Below the CMC of TC, taurocholate addition leads to vesicle growth due to incorporation of the taurocholate molecules into the vesicle bilayer. At around half the CMC of the bile salt, the SM vesicles are transformed into SM/TC mixed worm-like micelles, which are visualized by cryo-TEM for the first time. Further increase in the taurocholate concentration leads to the rupture of these structures into small spherical micelles. Interestingly, large non-spherical micelles were also identified for pure taurocholate solutions. Similar threadlike structures have been reported earlier for the bile salt sodium taurodeoxycholate [Rich, A., Blow, D., 1958. Nature 182, 1777; Blow, D.M., Rich, A., 1960. J. Am. Chem. Soc. 82, 3566–3571; Galantini, L., Giglio, E., La Mesa, C., Viorel-Pavel, N., Punzo, F., 2002. Langmuir 18, 2812] and for mixtures of taurocholate and phosphatidylcholate [Ulmius, J., Lindblom, G., Wennerström, H., Johansson, L.B.-Å., Fontel, K., Söderman, O., Ardvisson, G., 1982. Biochemistry 21, 1553; Hjelm, R.P., Thiyagarajan, P., Alkan-Onyuksel, H., 1992. J. Phys. Chem. 96, 8653] as determined by various scattering methods.

  • 18.
    Cárdenas, Marité
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Thomas, Robert
    Fragnetto, Giovanna
    Rennie, Adrian
    Lindh, Liselott
    Malmö högskola, Faculty of Odontology (OD).
    Human Saliva Forms a Complex Film Structure on Alumina Surfaces2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 1, p. 65-69Article in journal (Refereed)
    Abstract [en]

    Films formed from saliva on surfaces are important for maintenance of oral health and integrity by protection against chemical and/or biological agents. The aim of the present study was to investigate adsorbed amounts, thickness and the structure of films formed from human whole saliva on alumina surfaces by means of in situ ellipsometry, neutron reflectivity and atomic force microscopy. Alumina (Al2O3, synthetic sapphire) is a relevant and interesting substrate for saliva adsorption studies as it has an isoelectric point close to that of tooth enamel. The results showed that saliva adsorbs rapidly on alumina. The film could be modelled in two layers: an inner and dense thin region which forms a uniform layer, and an outer, more diffuse and thicker region that protrudes towards the bulk of the solution. The film morphology described a uniformly covering dense layer and a second outer layer containing polydisperse adsorbed macromolecules or aggregates.

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  • 19.
    Cárdenas, Marité
    et al.
    Malmö högskola, Faculty of Health and Society (HS). Malmö högskola, Faculty of Odontology (OD).
    Elofsson, Ulla
    Lindh, Liselott
    Malmö högskola, Faculty of Health and Society (HS). Malmö högskola, Faculty of Odontology (OD).
    Salivary mucin MUC5B could be an important component of in vitro pellicles of human saliva: an in situ ellipsometry and atomic force microscopy study2007In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 8, no 4, p. 1149-1156Article in journal (Refereed)
    Abstract [en]

    This paper describes a combined investigation of the salivary and MUC5B films structure and topography in conditions similar to those found in the oral cavity in terms of ionic strength, pH, and protein concentration. AFM and ellipsometry were successfully used to give a detailed picture of the film structure and topography both on hydrophilic and on hydrophobic substrata. Regardless of the substrata, the salivary film can be described as having a two sublayer structure in which an inner dense layer is decorated by large aggregates. However, the shape and height of these larger aggregates largely depend on the type of substrata used. Additionally, we show that the adsorption of MUC5B is controlled by the type of substrata and the MUC5B film topography is similar to that of the larger aggregates present in the salivary films, especially on hydrophobic substrates. Therefore, we conclude that MUC5B is a major component in the salivary film when formed on hydrophobic substrates. Furthermore, we studied how resistant the salivary and MUC5B films are against elutability by buffer rinsing and addition of SDS solution. We conclude that the adsorbed proteins contain fractions with varying binding strengths to the two types of surfaces. Specifically, we have shown that the large MUC5B biomacromolecules on the hydrophobic substrates are especially resistant to both elution with buffer solution and SDS. Therefore, these large mucins can be responsible for the increased resistance of HWS films on hydrophobic substrates and can protect the intraoral surfaces against surface-active components present in oral health care products.

  • 20.
    Engstedt, Jenni
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Camurus AB, Ideon Science Park, Gamma Building, Sölvegatan 41, SE-22379 Lund, Sweden.
    Barauskas, Justas
    Camurus AB, Ideon Science Park, Gamma Building, Sölvegatan 41, SE-22379 Lund, Sweden.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Phase behavior of soybean phosphatidylcholine and glycerol dioleate in hydrated and dehydrated states studied by small-angle X-ray scattering2023In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 19, no 43, p. 8305-8317Article in journal (Refereed)
    Abstract [en]

    Soybean phosphatidylcholine (SPC) and glycerol dioleate (GDO) form liquid crystal nanostructures in aqueous environments, and their mixtures can effectively encapsulate active pharmaceutical ingredients (API). When used in a subcutaneous environment, the liquid crystalline matrix gradually hydrates and degrades in the tissue whilst slowly releasing the API. Hydration dependent SPC/GDO phase behavior is complex, non-trivial, and still not fully understood. A deeper understanding of this system is important for controlling its function in drug delivery applications. The phase behavior of the mixture of SPC/GDO/water was studied as a function of hydration and lipid ratio. Small-angle X-ray scattering (SAXS) was used to identify space groups in liquid crystalline phases and to get detailed structural information on the isotropic reverse micellar phase. The reported pseudo ternary phase diagram includes eight different phases and numerous multiphase regions in a thermodynamically consistent way. For mixtures with SPC as the predominant component, the system presents a reverse hexagonal, lamellar and R3m phase. For mixtures with lower SPC concentrations, reverse cubic (Fd3m and Pm3n) as well as intermediate and isotropic micellar phases were identified. By modeling the SAXS data using a core–shell approach, the properties of the isotropic micellar phase were studied in detail as a function of concentration. Moreover, SAXS analysis of other phases revealed new structural features in relation to lipid–water interactions. The new improved ternary phase diagram offers valuable insight into the complex phase behavior of the SPC/GDO system. The detailed structural information is important for understanding what APIs can be incorporated in the liquid crystal structure.

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  • 21.
    Fagerström, Anton
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Kocherbitov, Vitaly
    Malmö högskola, Faculty of Health and Society (HS).
    Lamberg, Peter
    Malmö högskola, Faculty of Health and Society (HS).
    Bergström, Karin
    Westbye, Peter
    Ruzgas, Tautgirdas
    Malmö högskola, Faculty of Health and Society (HS).
    Engblom, Johan
    Malmö högskola, Faculty of Health and Society (HS).
    Factors Affecting Transport of Tebuconazole over Silicone Membrane and Leaf Cuticle2010In: Proceedings of the 9th International Symposium on Adjuvants for Agrochemicals, ISAA Society , 2010, p. 329-336Conference paper (Other academic)
  • 22.
    Gajdek, Dorotea
    et al.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Olsson, Pär A T
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Division of Mechanics, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Blomberg, Sara
    NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden;Department of Chemical Engineering, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Gustafson, Johan
    Division of Synchrotron Radiation Research, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Carlsson, Per-Anders
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden;Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
    Haase, Dörthe
    MAX IV Laboratory, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Lundgren, Edvin
    NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden;Division of Synchrotron Radiation Research, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Merte, Lindsay R.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). NanoLund, Lund University, Box 118, SE-221 00 Lund, Sweden.
    Structural Changes in Monolayer Cobalt Oxides under Ambient Pressure CO and O2 Studied by In Situ Grazing-Incidence X-ray Absorption Fine Structure Spectroscopy2022In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 126, no 7, p. 3411-3418Article in journal (Refereed)
    Abstract [en]

    We have used grazing incidence X-ray absorption fine structure spectroscopy at the cobalt K-edge to characterize monolayer CoO films on Pt(111) under ambient pressure exposure to CO and O2, with the aim of identifying the Co phases present and their transformations under oxidizing and reducing conditions. X-ray absorption near edge structure (XANES) spectra show clear changes in the chemical state of Co, with the 2+ state predominant under CO exposure and the 3+ state predominant under O2-rich conditions. Extended X-ray absorption fine structure spectroscopy (EXAFS) analysis shows that the CoO bilayer characterized in ultrahigh vacuum is not formed under the conditions used in this study. Instead, the spectra acquired at low temperatures suggest formation of cobalt hydroxide and oxyhydroxide. At higher temperatures, the spectra indicate dewetting of the film and suggest formation of bulklike Co3O4 under oxidizing conditions. The experiments demonstrate the power of hard X-ray spectroscopy to probe the structures of well-defined oxide monolayers on metal single crystals under realistic catalytic conditions.

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  • 23.
    Galvagnion, Celine
    et al.
    Univ Copenhagen, Dept Drug Design & Pharmacol, DK-2100 Copenhagen, Denmark..
    Barclay, Abigail
    Univ Copenhagen, Niels Bohr Inst, DK-2100 Copenhagen, Denmark..
    Makasewicz, Katarzyna
    Lund Univ, Div Phys Chem, Ctr Chem & Chem Engn, POB 124, SE-22100 Lund, Sweden..
    Marlet, Frederik Ravnkilde
    Univ Copenhagen, Dept Drug Design & Pharmacol, DK-2100 Copenhagen, Denmark..
    Moulin, Martine
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Devos, Juliette M.
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Linse, Sara
    Lund Univ, Dept Biochem & Struct Biol, SE-22100 Lund, Sweden..
    Martel, Anne
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Porcar, Lionel
    Inst Laue Langevin, 71 Ave Martyrs, F-38042 Grenoble, France..
    Sparr, Emma
    Lund Univ, Div Phys Chem, Ctr Chem & Chem Engn, POB 124, SE-22100 Lund, Sweden..
    Pedersen, Martin Cramer
    Univ Copenhagen, Niels Bohr Inst, DK-2100 Copenhagen, Denmark..
    Roosen-Runge, Felix
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Lund Univ, Div Phys Chem, Ctr Chem & Chem Engn, POB 124, SE-22100 Lund, Sweden..
    Arleth, Lise
    Univ Copenhagen, Niels Bohr Inst, DK-2100 Copenhagen, Denmark..
    Buell, Alexander K.
    Tech Univ Denmark, Dept Biotechnol & Biomed, DK-2800 Kongens, Denmark..
    Structural characterisation of α-synuclein-membrane interactions and the resulting aggregation using small angle scattering2024In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 26, no 14, p. 10998-11013Article in journal (Refereed)
    Abstract [en]

    The presence of amyloid fibrils is a hallmark of several neurodegenerative diseases. Some amyloidogenic proteins, such as alpha-synuclein and amyloid beta, interact with lipids, and this interaction can strongly favour the formation of amyloid fibrils. In particular the primary nucleation step, i.e. the de novo formation of amyloid fibrils, has been shown to be accelerated by lipids. However, the exact mechanism of this acceleration is still mostly unclear. Here we use a range of scattering methods, such as dynamic light scattering (DLS) and small angle X-ray and neutron scattering (SAXS and SANS) to obtain structural information on the binding of alpha-synuclein to model membranes formed from negatively charged lipids and their co-assembly into amyloid fibrils. We find that the model membranes take an active role in the reaction. The binding of alpha synuclein to the model membranes immediately induces a major structural change in the lipid assembly, which leads to a break-up into small and mostly disc- or rod-like lipid-protein particles. This transition can be reversed by temperature changes or proteolytic protein removal. Incubation of the small lipid-alpha-synuclein particles for several hours, however, leads to amyloid fibril formation, whereby the lipids are incorporated into the amyloid fibrils. alpha S binding to DLPS and DMPS leads to a ms fast reversible deformation into disks and rods. Upon further incubation, lipid rods elongate within the same time scale as that of amyloid formation confirming lipids co-assembly with alpha S into fibrils.

  • 24.
    Garcia-Martinez, Fernando
    et al.
    Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, 20018 San Sebastian, Spain.
    Dietze, Elisabeth
    Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Schiller, Frederik
    Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, 20018 San Sebastian, Spain.
    Gajdek, Dorotea
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Merte, Lindsay R.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden.
    Gericke, Sabrina M
    Combustion Physics, Lund University, Box 118, 22100 Lund, Sweden.
    Zetterberg, Johan
    Combustion Physics, Lund University, Box 118, 22100 Lund, Sweden.
    Albertin, Stefano
    Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden..
    Lundgren, Edvin
    Synchrotron Radiation Research, Lund University, 22100 Lund, Sweden..
    Grönbeck, Henrik
    Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Ortega, J Enrique
    Centro de Física de Materiales CSIC/UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, 20018 San Sebastian, Spain; Departamento Física Aplicada, Universidad del País Vasco, 20018 San Sebastian, Spain; Donostia International Physics Centre, 20018 San Sebastian, Spain.
    Reduced Carbon Monoxide Saturation Coverage on Vicinal Palladium Surfaces: the Importance of the Adsorption Site2021In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 12, no 39, p. 9508-9515Article in journal (Refereed)
    Abstract [en]

    Steps at metal surfaces may influence energetics and kinetics of catalytic reactions in unexpected ways. Here, we report a significant reduction of the CO saturation coverage in Pd vicinal surfaces, which in turn is relevant for the light-off of the CO oxidation reaction. The study is based on a systematic investigation of CO adsorption on vicinal Pd(111) surfaces making use of a curved Pd crystal. A combined X-ray Photoelectron Spectroscopy and DFT analysis allows us to demonstrate that an entire row of atomic sites under Pd steps remains free of CO upon saturation at 300 K, leading to a step-density-dependent reduction of CO coverage that correlates with the observed decrease of the light-off temperature during CO oxidation in vicinal Pd surfaces.

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  • 25.
    Garcia-Martinez, Fernando
    et al.
    Centro de Física de Materiales CSIC/UPV-EHU-, Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastian, Spain.
    Garcia-Fernandez, Carlos
    Centro de Física de Materiales CSIC/UPV-EHU-, Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastian, Spain.
    Simonovis, Juan Pablo
    National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
    Hunt, Adrian
    National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
    Walter, Andrew
    National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
    Waluyo, Iradwikanari
    National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
    Bertram, Florian
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Merte, Lindsay R.
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Shipilin, Mikhail
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Pfaff, Sebastian
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Blomberg, Sara
    Department of Chemical Engineering, Lund University, 221 000, Lund, Sweden.
    Zetterberg, Johan
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Gustafson, Johan
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Lundgren, Edvin
    Department of Physics, Lund University, 221 000, Lund, Sweden.
    Sanchez-Portal, Daniel
    Centro de Física de Materiales CSIC/UPV-EHU-, Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastian, Spain.
    Schiller, Frederik
    Centro de Física de Materiales CSIC/UPV-EHU-, Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastian, Spain.
    Ortega, Enrique
    Centro de Física de Materiales CSIC/UPV-EHU-, Materials Physics Center, Manuel Lardizabal 5, 20018, San Sebastian, Spain; Departamento Física Aplicada I, Universidad del País Vasco, 20018, San Sebastian, Spain; Donostia International Physics Centre, Paseo Manuel de Lardizabal 4, 20018, San Sebastian, Spain.
    Catalytic oxidation of CO on a curved Pt(111) surface: simultaneous ignition at all facets through a transient CO-O complex.2020In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 59, no 45, p. 20037-20043Article in journal (Refereed)
    Abstract [en]

    The catalytic oxidation of carbon monoxide (CO) on transition metals, such as platinum (Pt), is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with oxygen (O). However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. The systematic analysis of carbon and oxygen core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces, as indicated by ab-initio theory: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature.

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  • 26.
    Garcia-Martinez, Fernando
    et al.
    Centro de Fĺsica de Materiales CSIC, UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, San Sebastian, 20018, Spain.
    Schiller, Frederik
    Centro de Fĺsica de Materiales CSIC, UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, San Sebastian, 20018, Spain.
    Blomberg, Sara
    Synchrotron Radiation Research, Lund University, Lund, 22100, Sweden; Department of Chemical Engineering, Lund University, Lund, 22100, Sweden.
    Shipilin, Mikhail
    Synchrotron Radiation Research, Lund University, Lund, 22100, Sweden; Department of Physics, AlbaNova University Center, Stockholm University, Stockholm, 10691, Sweden.
    Merte, Lindsay R.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Synchrotron Radiation Research, Lund University, Lund, 22100, Sweden.
    Gustafson, Johan
    Synchrotron Radiation Research, Lund University, Lund, 22100, Sweden.
    Lundgren, Edvin
    Synchrotron Radiation Research, Lund University, Lund, 22100, Sweden.
    Enrique Ortega, J.
    Centro de Fĺsica de Materiales CSIC, UPV-EHU-Materials Physics Center, Manuel Lardizabal 5, San Sebastian, 20018, Spain; Departamento Fĺsica Aplicada i, Universidad Del Paĺs Vasco, San Sebastian, 20018, Spain; Donostia International Physics Centre, Paseo Manuel de Lardizabal 4, San Sebastian, 20018, Spain.
    CO Chemisorption on Vicinal Rh(111) Surfaces Studied with a Curved Crystal2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 17, p. 9305-9313Article in journal (Refereed)
    Abstract [en]

    Curved crystal surfaces enable the systematic and accurate comparison of physical and chemical processes for a full set of vicinal crystal planes, which are probed in the very same environment. Here, we examine the early stages of the CO chemisorption on vicinal Rh(111) surfaces using a curved Rh crystal that exposes a smoothly variable density of {100} (A-type) and {111} (B-type) steps. We readily identify and quanti step and terrace species by resolving their respective core-level lines using X-ray photoelectron spectroscopy at different locations on the curved surface. Uptake experiments show similar sticking probabilities at all surface planes, subtle asymmetries between A- and B-type steps, and significantly lower saturation coverage at densely stepped surfaces as compared to the (111) plane. The analysis of the C is intensity variation across the curved sample allows us to discuss the adsorption geometry around the step edge.

  • 27.
    Gerelli, Yuri
    et al.
    Italian National Research Council – Institute for Complex Systems (CNR-ISC) and Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy.
    Camerin, Fabrizio
    Division of Physical Chemistry, Lund University, P. O. Box 124, SE-22100 Lund, Sweden.
    Bochenek, Steffen
    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany.
    Schmidt, Maximilian M
    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany.
    Maestro, Armando
    Centro de Física de Materiales (CSIC, UPV/EHU) – Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; IKERBASQUE-Basque Foundation for Science, Plaza Euskadi 5, Bilbao, Spain; Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France.
    Richtering, Walter
    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany.
    Zaccarelli, Emanuela
    Italian National Research Council – Institute for Complex Systems (CNR-ISC) and Department of Physics, Sapienza University of Rome, Piazzale Aldo Moro 2, 00185 Rome, Italy.
    Scotti, Andrea
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Softness matters: effects of compression on the behavior of adsorbed microgels at interfaces.2024In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 20, no 17, p. 3653-3665Article in journal (Refereed)
    Abstract [en]

    Deformable colloids and macromolecules adsorb at interfaces as they decrease the interfacial energy between the two media. The deformability, or softness, of these particles plays a pivotal role in the properties of the interface. In this study, we employ a comprehensive in situ approach, combining neutron reflectometry with molecular dynamics simulations, to thoroughly examine the profound influence of softness on the structure of microgel Langmuir monolayers under compression. Lateral compression of both hard and soft microgel particle monolayers induces substantial structural alterations, leading to an amplified protrusion of the microgels into the aqueous phase. However, a critical distinction emerges: hard microgels are pushed away from the interface, in stark contrast to the soft ones, which remain firmly anchored to it. Concurrently, on the air-exposed side of the monolayer, lateral compression induces a flattening of the surface of the hard monolayer. This phenomenon is not observed for the soft particles as the monolayer is already extremely flat even in the absence of compression. These findings significantly advance our understanding of the key role of softness on both the equilibrium phase behavior of the monolayer and its effect when soft colloids are used as stabilizers of responsive interfaces and emulsions.

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  • 28.
    Gericke, Sabrina Maria
    et al.
    Division of Combustion Physics, Lunds University, P.O. Box 118, 221 00 Lund, Sweden.
    Rissler, Jenny
    RISE—Research Institutes of Sweden, P.O. Box 857, 501 15 Borås, Sweden; NanoLund, Lund University, P.O. Box 188, 221 00 Lund, Sweden; Ergonomics and Aerosol Technology, Faculty of Engineering, Lund University, P.O. Box 118, 221 00 Lund, Sweden.
    Bermeo, Marie
    NanoLund, Lund University, P.O. Box 188, 221 00 Lund, Sweden; Solid State Physics, Lund University, 221 00 Lund, Sweden.
    Wallander, Harald J.
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Karlsson, Hanna
    Department of Chemical Engineering, Lund University, 221 00 Lund, Sweden.
    Kollberg, Linnéa
    Department of Chemical Engineering, Lund University, 221 00 Lund, Sweden.
    Scardamaglia, Mattia
    MAX IV Laboratory, Lund University, 221 00 Lund, Sweden.
    Temperton, Robert
    MAX IV Laboratory, Lund University, 221 00 Lund, Sweden.
    Zhu, Suyun
    MAX IV Laboratory, Lund University, 221 00 Lund, Sweden.
    Sigfridsson Clauss, Kajsa G. V.
    MAX IV Laboratory, Lund University, 221 00 Lund, Sweden.
    Hulteberg, Christian
    Department of Chemical Engineering, Lund University, 221 00 Lund, Sweden.
    Shavorskiy, Andrey
    MAX IV Laboratory, Lund University, 221 00 Lund, Sweden.
    Merte, Lindsay Richard
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Messing, Maria Elise
    NanoLund, Lund University, P.O. Box 188, 221 00 Lund, Sweden; Solid State Physics, Lund University, 221 00 Lund, Sweden.
    Zetterberg, Johan
    Division of Combustion Physics, Lunds University, P.O. Box 118, 221 00 Lund, Sweden.
    Blomberg, Sara
    Department of Chemical Engineering, Lund University, 221 00 Lund, Sweden.
    In Situ H2 Reduction of Al2O3-Supported Ni- and Mo-Based Catalysts2022In: Catalysts, E-ISSN 2073-4344, Vol. 12, no 7, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Nickel (Ni)-promoted Molybdenum (Mo)-based catalysts are used for hydrotreatment processes in the chemical industry where the catalysts are exposed to high-pressure H2 at elevated temperature. In this environment, the catalyst transforms into the active phase, which involves the reduction of the oxide. Here, we report on the first in situ study on the reduction of alumina supported Ni- and Mo-based catalysts in 1 mbar H2 using ambient-pressure X-ray photoelectron spectroscopy (APXPS). The study confirms that mixing Ni and Mo lowers the reduction temperature of both Ni- and Mo-oxide as compared to the monometallic catalysts and shows that the MoO3 reduction starts at a lower temperature than the reduction of NiO in NiMo/Al2O3 catalysts. Additionally, the reduction of Ni and Mo foil was directly compared to the reduction of the Al2O3-supported catalysts and it was observed that the reduction of the supported catalysts is more gradual than the reduction of the foils, indicating a strong interaction between the Ni/Mo and the alumina support.

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  • 29.
    Gonzalez-Martinez, Juan F
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Boyd, Hannah
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Gutfreund, Philipp
    Institut Laue Langevin, 71 avenue des Martyrs, Grenoble 38000, France.
    Welbourn, Rebecca J L
    ISIS Facility, STFC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, United Kingdom.
    Robertsson, Carolina
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Wickström, Claes
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Arnebrant, Thomas
    Malmö University, Biofilms Research Center for Biointerfaces. Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    Richardson, Robert M
    School of Physics, University of Bristol, Tyndall Avenue, BS8 1TL Bristol, United Kingdom.
    Prescott, Stuart W
    School of Chemical Engineering, University of New South Wales, Sydney, NSW 2052, Australi.
    Barker, Robert
    School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, United Kingdom.
    Sotres, Javier
    Malmö University, Biofilms Research Center for Biointerfaces. Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    MUC5B mucin films under mechanical confinement: A combined neutron reflectometry and atomic force microscopy study.2022In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 614, p. 120-129, article id S0021-9797(22)00109-6Article in journal (Refereed)
    Abstract [en]

    HYPOTHESIS: Among other functions, mucins hydrate and protect biological interfaces from mechanical challenges. Mucins also attract interest as biocompatible coatings with excellent lubrication performance. Therefore, it is of high interest to understand the structural response of mucin films to mechanical challenges. We hypothesized that this could be done with Neutron Reflectometry using a novel sample environment where mechanical confinement is achieved by inflating a membrane against the films.

    EXPERIMENTS: Oral MUC5B mucin films were investigated by Force Microscopy/Spectroscopy and Neutron Reflectometry both at solid-liquid interfaces and under mechanical confinement.

    FINDINGS: NR indicated that MUC5B films were almost completely compressed and dehydrated when confined at 1 bar. This was supported by Force Microscopy/Spectroscopy investigations. Force Spectroscopy also indicated that MUC5B films could withstand mechanical confinement by means of steric interactions for pressures lower than ∼ 0.5 bar i.e., mucins could protect interfaces from mechanical challenges of this magnitude while keeping them hydrated. To investigate mucin films under these pressures by means of the employed sample environment for NR, further technological developments are needed. The most critical would be identifying or developing more flexible membranes that would still meet certain requirements like chemical homogeneity and very low roughness.

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  • 30.
    Gunnarsson, Maria
    et al.
    Division of Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
    Mojumdar, Enamul Haque
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Division of Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
    Topgaard, Daniel
    Division of Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
    Sparr, Emma
    Division of Physical Chemistry, Department of Chemistry, Lund University, Box 124, SE-221 00 Lund, Sweden.
    Extraction of natural moisturizing factor from the stratum corneum and its implication on skin molecular mobility2021In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 604, p. 480-491, article id S0021-9797(21)01070-5Article in journal (Refereed)
    Abstract [en]

    The natural moisturizing factor (NMF) is a mixture of small water-soluble compounds present in the upper layer of the skin, stratum corneum (SC). Soaking of SC in water leads to extraction of the NMF molecules, which may influence the SC molecular properties and lead to brittle and dry skin. In this study, we investigate how the molecular dynamics in SC lipid and protein components are affected by the removal of the NMF compounds. We then explore whether the changes in SC components caused by NMF removal can be reversed by a subsequent addition of one single NMF component: urea, pyrrolidone carboxylic acid (PCA) or potassium lactate. Samples of intact SC were investigated using NMR, X-ray diffraction, infrared spectroscopy and sorption microbalance. It is shown that the removal of NMF leads to reduced molecular mobility in keratin filaments and SC lipids compared to untreated SC. When the complex NMF mixture is replaced by one single NMF component, the molecular mobility in both keratin filaments and lipids is regained. From this we propose a general relation between the molecular mobility in SC and the amount of polar solutes which does not appear specific to the precise chemical identify of the NMF compounds.

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  • 31.
    Hagman, Benjamin
    et al.
    Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden.
    Posada-Borbon, Alvaro
    Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Schaefer, Andreas
    Department of Chemistry and Chemical Engineering and Competence Centre for Catalysis, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Shipilin, Mikhail
    Department of Physics, AlbaNova University Center, Stockholm University, 106 91 Stockholm, Sweden.
    Zhang, Chu
    Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden.
    Merte, Lindsay Richard
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM).
    Hellman, Anders
    Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Lundgren, Edvin
    Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden.
    Grönbeck, Henrik
    Department of Physics and Competence Centre for Catalysis, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
    Gustafson, Johan
    Synchrotron Radiation Research, Lund University, Box 118, 221 00 Lund, Sweden.
    Steps Control the Dissociation of CO2 on Cu(100)2018In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 140, no 40, p. 12974-12979Article in journal (Refereed)
    Abstract [en]

    CO2 reduction reactions, which provide one route to limit the emission of this greenhouse gas, are commonly performed over Cu-based catalysts. Here, we use ambient pressure X-ray photoelectron spectroscopy together with density functional theory to obtain an atomistic understanding of the dissociative adsorption of CO2 on Cu(100). We find that the process is dominated by the presence of steps, which promote both a lowering of the dissociation barrier and an efficient separation between adsorbed O and CO, reducing the probability for recombination. The identification of steps as sites for efficient CO2 dissociation provides an understanding that can be used in the design of future CO2 reduction catalysts.

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  • 32. Hahn Berg, Cecilia I
    et al.
    Lindh, Liselott
    Malmö högskola, Faculty of Odontology (OD). Malmö högskola, Faculty of Health and Society (HS).
    Arnebrant, Thomas
    Malmö högskola, Faculty of Odontology (OD). Malmö högskola, Faculty of Health and Society (HS).
    Intraoral Lubrication of PRP-1, Statherin and Mucin as Studied by AFM2004In: Biofouling (Print), ISSN 0892-7014, E-ISSN 1029-2454, Vol. 20, no 1, p. 65-70Article in journal (Refereed)
    Abstract [en]

    The aim of this paper was to elucidate the mechanisms behind salivary lubrication with special emphasis on the lubricity of three key components of the pellicle, viz human acidic proline-rich protein 1 (PRP-1), human statherin and bovine submaxillary mucin (BSM). The lubricating properties of the proteins have been assessed by means of colloidal probe atomic force microscopy, and are discussed in relation to their adsorption behaviour. To various extents, the proteins investigated all showed a lubricating effect when adsorbed to silica surfaces. For comparable concentrations, PRP-1 was found to have a more pronounced lubricating effect than BSM, which in turn showed a higher lubricity than statherin. The relative lubricity is in accordance with previously reported relative adsorbed amounts of the three proteins, within the investigated concentration interval. It is concluded that PRP-1 has the highest lubricating capacity as a pure fraction among the preparations investigated, and that the lubricating effect of PRP-1 as a pure fraction is notably large as compared to the lubricity of human whole saliva.

  • 33.
    Hayashi, Mariko
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Jimbo, R.
    Xue, Y.
    Mustafa, K.
    Andersson, M.
    Wennerberg, Ann
    Malmö högskola, Faculty of Odontology (OD).
    Photocatalytically induced hydrophilicity influences bone remodelling at longer healing periods: a rabbit study2014In: Clinical Oral Implants Research, ISSN 0905-7161, E-ISSN 1600-0501, Vol. 25, no 6, p. 749-754Article in journal (Refereed)
    Abstract [en]

    ObjectivesPreviously, we have reported that photocatalytically active hydrophilicity of the anatase titanium dioxide (TiO2) nanoparticles coated onto commercially pure titanium discs presented significantly improved hydrophilicity after ultraviolet irradiation. As hydrophilicity has shown enhancement of osseointegration, the in vivo responses were of great interest. The aim of this study was to evaluate whether or not the photo-activated hydrophilicity generated at the time of implant placement has an effect on the longer healing periods for osseointegration. Materials and methodsPhotocatatytically active nanostructured TiO2 powder (Degussa P-25), which consists of approximately 80% anatase and 20% rutile, was spin-coated onto commercially pure titanium discs and was heat-treated thereafter. These P25-coated discs were irradiated with ultraviolet (UV) light for the test (+UV) group, and non-irradiated discs were prepared for the control (-UV) group. Both groups of discs were placed in the rabbits' tibiae. After 12weeks of healing period, histological analysis and gene expression analysis using real-time RT-PCR were performed. ResultsFrom the histological analyses, there were no specific differences between -UV and +UV groups. However, from the gene expression analysis, ALP, RUNX-2 and IL-10 were significantly upregulated for the +UV group compared with the -UV group. ConclusionsThe biologically enhancing effect to photocatalytically activated surfaces remained even after 12weeks of healing time in terms of genetic responses.

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  • 34.
    Hirschmann, Frank
    et al.
    Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Lopez, Hender
    School of Physics, Clinical and Optometric Sciences, Technological University Dublin, Grangegorman D07 ADY7, Ireland.
    Roosen-Runge, Felix
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Seydel, Tilo
    Institut Max von Laue—Paul Langevin, 71 Avenue des Martyrs, 38042 Grenoble, France.
    Schreiber, Frank
    Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Oettel, Martin
    Institute for Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Effects of flexibility in coarse-grained models for bovine serum albumin and immunoglobulin G2023In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 158, no 8, article id 084112Article in journal (Refereed)
    Abstract [en]

    We construct a coarse-grained, structure-based, low-resolution, 6-bead flexible model of bovine serum albumin (BSA, PDB: 4F5S), which is a popular example of a globular protein in biophysical research. The model is obtained via direct Boltzmann inversion using all-atom simulations of a single molecule, and its particular form is selected from a large pool of 6-bead coarse-grained models using two suitable metrics that quantify the agreement in the distribution of collective coordinates between all-atom and coarse-grained Brownian dynamics simulations of solutions in the dilute limit. For immunoglobulin G (IgG), a similar structure-based 12-bead model has been introduced in the literature [Chaudhri et al., J. Phys. Chem. B 116, 8045 (2012)] and is employed here to compare findings for the compact BSA molecule and the more anisotropic IgG molecule. We define several modified coarse-grained models of BSA and IgG, which differ in their internal constraints and thus account for a variation of flexibility. We study denser solutions of the coarse-grained models with purely repulsive molecules (achievable by suitable salt conditions) and address the effect of packing and flexibility on dynamic and static behavior. Translational and rotational self-diffusivity is enhanced for more elastic models. Finally, we discuss a number of effective sphere sizes for the BSA molecule, which can be defined from its static and dynamic properties. Here, it is found that the effective sphere diameters lie between 4.9 and 6.1 nm, corresponding to a relative spread of about ±10% around a mean of 5.5 nm.

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  • 35.
    Höfken, Tom
    et al.
    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
    Gasser, Urs
    Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland.
    Schneider, Stefanie
    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
    Petrunin, Alexander V
    Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
    Scotti, Andrea
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    Real and In-Silico Microgels Show Comparable Bulk Moduli Below and Above the Volume Phase Transition.2024In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, article id e2400043Article in journal (Refereed)
    Abstract [en]

    The compressibility of soft colloids influences their phase behavior and flow properties, especially in concentrated suspensions. Particle compressibility, which is proportional to the reciprocal of the bulk modulus K, is a key parameter for soft polymer-based particles that can be compressed in crowded environments. Here, microgels with different degrees of crosslinking, i.e. softness, are investigated below and above their volume phase transition temperature VPTT. By combining molecular dynamics simulations with small-angle neutron scattering with contrast variation, a change in the particle bulk moduli of two orders of magnitude is observed. The degree of crosslinking has a significant impact on the bulk modulus of the swollen microgel, while above the VPTT the values of K are almost independent of the crosslinking density. The excellent agreement between experimental results and simulations also highlight that the model microgels posses both the internal architecture and the elastic properties of real polymeric networks. This paves the way to a systematic use of simulations to investigate the behavior of dense microgel suspensions. This article is protected by copyright. All rights reserved.

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  • 36.
    Kamal, Md Arif
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Raman Res Inst, C V Raman Ave, Bangalore 560080, Karnataka, India.
    Pal, Antara
    Raman Res Inst, C V Raman Ave, Bangalore 560080, Karnataka, India.;Stockholm Univ, Dept Phys, Stockholm, Sweden.;MAX IV Lab, Lund, Sweden..
    Effect of Desmosterol, Lathosterol and Coprostanol on the phase behaviour of phospholipid membranes2023In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 673, article id 131489Article in journal (Refereed)
    Abstract [en]

    Sterols have played an important role in membrane evolution. The effect of these molecules, particularly the naturally occurring ones, such as cholesterol, ergosterol, lanosterol, phytosterols and oxysterols on the prop-erties of lipid model membranes have been extensively investigated. Unfortunately, other naturally occurring sterols such as desmosterol and lathosterol have received very little attention. Using small angle X-ray scattering (SAXS), we have carried out detailed investigations on the influence of desmosterol and lathosterol along with coprostanol on the phase behaviour of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes. SAXS results indicate both that these sterols modulate the properties of the DPPC bilayer in a manner similar to cholesterol. However, we have found desmosterol to be more efficient than cholesterol in suppressing the main transition of DPPC, with the fluid phase stabilized at around 15 mol% (compared to around 20 mol% in cholesterol). Coprostanol on the other hand was found to be less efficient in stabilizing the fluid phase than the other two. The results obtained from our study in combination with those existing in the literature will help in establishing a complete picture of how different sterols influence the properties of lipid membranes.

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  • 37.
    Kamal, Mohammad Arif
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Lund Univ, Dept Chem, Div Phys Chem, Lund, Sweden..
    Brizioli, Matteo
    Univ Milan, Dept Med Biotechnol & Translat Med, Milan, Italy..
    Zinn, Thomas
    ESRF European Synchrotron, Grenoble, France.;Diamond Light Source Ltd, Didcot, England..
    Narayanan, Theyencheri
    ESRF European Synchrotron, Grenoble, France..
    Cerbino, Roberto
    Univ Vienna, Fac Phys, Vienna, Austria..
    Giavazzi, Fabio
    Univ Milan, Dept Med Biotechnol & Translat Med, Milan, Italy..
    Pal, Antara
    Stockholm Univ, Dept Phys, Stockholm, Sweden.;MAX IV Lab, Lund, Sweden..
    Dynamics of anisotropic colloidal systems: What to choose, DLS, DDM or XPCS?2024In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 660, p. 314-320Article in journal (Refereed)
    Abstract [en]

    Investigation of the dynamics of colloids in bulk can be hindered by issues such as multiple scattering and sample opacity. These challenges are exacerbated when dealing with inorganic materials. In this study, we employed a model system of Akaganeite colloidal rods to assess three leading dynamics measurement techniques: 3D -(depolarized) dynamic light scattering (3D-(D)DLS), polarized -differential dynamic microscopy (P-DDM), and x-ray photon correlation spectroscopy (XPCS). Our analysis revealed that the translational and rotational diffusion coefficients captured by these methods show a remarkable alignment. Additionally, by examining the q -ranges and maximum volume fractions for each approach, we offer insights into the best technique for investigating the dynamics of anisotropic systems at the colloidal scale.

  • 38.
    Kocherbitov, V
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Söderman, Olle
    Physical Chemistry 1, Center for Chemistry and Chemical Engineering, P.O. Box 124, Lund University, SE-221 00 Lund, Sweden.
    Lysozyme-Water Interactions Studied by Sorption Calorimetry2004In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 108, no 49, p. 19036-19042Article in journal (Refereed)
    Abstract [en]

    Hydration of hen egg white lysozyme was studied by using the method of sorption calorimetry at 25, 40, and 50 °C. Desorption calorimetric measurements were performed at 25 and 40 °C. The activity of water and partial molar enthalpy of mixing of water were determined as functions of water content. Hydration of lysozyme occurs in four steps:  slow penetration of water into the protein−protein interface; gradual glass transition, which occurs in every protein molecule independently of other molecules; further water uptake with disaggregation of protein aggregates and formation of a monolayer of water; and accumulation of free water. The amount of bound water found in desorption experiments is 420 water molecules per lysozyme molecule. Two hysteresis loops were found in the sorption isotherm of lysozyme. The small loop is caused by the slow penetration of water molecules into the protein−protein interface at very low water contents, while the large loop is due to the slow kinetics of aggregation of protein molecules upon desorption. The phase diagram of the lysozyme−water system is presented. 

  • 39.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    On the calculation of thermodynamic parameters in sorption calorimetric experiments2021In: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 152, article id 106264Article in journal (Refereed)
    Abstract [en]

    The sorption calorimetry method developed by Wadso and co-workers is one of the most successful methods for studying the enthalpy of vapor sorption by solids and gels. A unique feature of this method is a simultaneous measurement of the water sorption isotherm and the sorption enthalpy. The accuracy of the enthalpy measurements in sorption calorimetric experiments can be affected by diffusion of water vapour through the injection channel tube and potentially through small leaks in the sorption cell. At high water activities this leads to an apparent drift of the measured enthalpies towards endothermic values. In this work we propose an improvement of the enthalpy calculation method, that eliminates these effects and substantially improves the accuracy of the enthalpy measurements. The new method is successfully tested on previously published sorption calorimetric data and can be recommended for use in future experiments. (C) 2020 The Author(s). Published by Elsevier Ltd.

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  • 40.
    Kocherbitov, Vitaly
    Malmö högskola, Faculty of Health and Society (HS).
    Properties of Water Confined in an Amphiphilic Nanopore2008In: J. Phys. Chem. C, Vol. 112, p. 16893-16897Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations of water and nitrogen confined in a model amphiphilic nanotube were performed. The nanotube has a diameter of 4 nm and consists of hydrophobic atoms and regularly placed OH groups. The results show that the density of water close to the nanotube walls is lower compared to the density in the center of the nanotube. The hydrogen bonded network of water molecules is practically intact compared with the bulk water. The simulation confirms that the experimentally observed low formal density of water in the nanopores (0.88 g/cm3) is due to formation of small unfilled cavities adjacent to the pore walls. Nitrogen molecules are localized primarily in the unhydrated cavities. The presence of nitrogen molecules is not the main reason for the decrease of water density in the nanotube.

  • 41.
    Kocherbitov, Vitaly
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Alfredsson, Viveka
    Hydration of MCM-41 Studied by Sorption Calorimetry2007In: J. Phys. Chem. C, no 2007, 111 (35)Article in journal (Refereed)
    Abstract [en]

    Hydration of mesoporous silica MCM-41 was studied using the method of sorption calorimetry. By combining water sorption and nitrogen sorption experiments, we calculated the density of silanol groups on the MCM-41 surface as 1.6 nm-2. Comparison of capillary condensation regimes of water and nitrogen showed that the apparent density of water confined in MCM-41 pores is ca. 0.88 g/cm3. The pore diameter calculated using a combination of X-ray and sorption data is 39 Å. Calculations based on application of the Kelvin-Cohan equation on the water sorption data are in reasonable agreement with this value. The sorption calorimetric results show that the capillary condensation of water in the pores is driven by enthalpy; the entropic effect is negative. A mechanism of hydration that involves formation of small unfilled cavities adjacent to pore walls can be used to explain the observed enthalpy end entropy effects. Comparison of sorption and desorption data indicates the presence of air trapped in pores when hydration is performed by mixing MCM-41 with liquid water. The heat effect of pre-capillary condensation adsorption of water on hydroxylated MCM-41 is much more exothermic compared to the original calcined material.

  • 42.
    Kocherbitov, Vitaly
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Argatov, Ivan
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Malmö University, Biofilms Research Center for Biointerfaces. Tech Univ Berlin, Inst Mech, D-10623 Berlin, Germany..
    A thermodynamic theory of sorption in glassy polymers2021In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 233, article id 124195Article in journal (Refereed)
    Abstract [en]

    Sorption of vapors by glassy polymers is known to have properties that are different from those typical for sorption by rubbery polymers or liquids. Despite an importance for many practical applications, this difference is still not fully understood. We developed a thermodynamic theory for description of penetrant activity in the glassy state. The presented approach considers the glass transition in terms of a second order phase transition and utilizes heat capacity changes for calculation of thermodynamic activity. The formalism developed here explains a deviation of penetrant activity in the glassy state from equilibrium values. Moreover, the sorption-desorption hysteresis can be explained in thermodynamic terms as well. We demonstrate that not only the heat capacity change of the polymer, but also the heat capacity change of the penetrant should be considered to understand the difference between three cases: sorption by equilibrium liquid, absorption by glass and desorption from glass. The theory presented here is tested on experimental data on water sorption by maltodextrin and bovine submaxillary gland mucin. A very good fitting of the experimental data for both sorption and desorption cases is demonstrated. The values of heat capacity increments of the components obtained by fitting the penetrant activity data can be used to get new insights into the non-equilibrium properties of glassy materials.

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  • 43.
    Kocherbitov, Vitaly
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Hydration of lysozyme: the protein-protein interface and the enthalpy-entropy compensation2010In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, no 6, p. 3918-3922Article in journal (Refereed)
    Abstract [en]

    Water sorption isotherms of proteins are usually interpreted with such models as BET or GAB that imply the formation of multilayers at solid-gas interface. However, this approach is not applicable to globular proteins such as humid lysozyme where a solid-gas interface does not exist. Another popular approach is the D’Arcy-Watt model, where besides the formation of multilayers the heterogeneity of energies of sorption sites of proteins is taken into account. Here we present sorption calorimetric data on the hydration of lysozyme that confirms the existence of the heterogeneity. The magnitude of the heterogeneity is, however, lower than one can expect on the basis of the existence of a solid-gas interface. Moreover, the calorimetric data show a strong enthalpy-entropy compensation that leads to almost constant effective free energy of hydration in the activity range normally used for fitting the data to sorption models. This allows the use of the Langmuir equation for the fitting of the initial part of the sorption isotherm of lysozyme. Assuming the formation of a monolayer of water at the protein-protein interface, one can estimate the size of the lysozyme molecules from the sorption isotherm. The result of this estimation is in good agreement with the structural data on lysozyme, which supports the presented approach.

  • 44.
    Kocherbitov, Vitaly
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Hydration of Thermally Denatured Lysozyme Studied by Sorption Calorimetry and Differential Scanning Calorimetry2006In: J.Phys.Chem.B., Vol. 110, p. 10144-10150Article in journal (Refereed)
    Abstract [en]

    We have studied hydration (and dehydration) of thermally denatured hen egg lysozyme using sorption calorimetry. Two different procedures of thermal denaturation of lysozyme were used. In the first procedure the protein was denatured in an aqueous solution at 90 °C, in the other procedure a sample that contained 20% of water was denatured at 150 °C. The protein denatured at 90 °C showed very similar sorption behavior to that of the native protein. The lysozyme samples denatured at 150 °C were studied at several temperatures in the range of 25-60 °C. In the beginning of sorption, the sorption isotherms of native and denatured lysozyme are almost identical. At higher water contents, however, the denatured lysozyme can absorb a greater amount of water than the native protein due to the larger number of available sorption sites. Desorption experiments did not reveal a pronounced hysteresis in the sorption isotherm of denatured lysozyme (such hysteresis is typical for native lysozyme). Despite the unfolded structure, the denatured lysozyme binds less water than does the native lysozyme in the desorption experiments at water contents up to 34 wt %. Glass transitions in the denatured lysozyme were observed using both differential scanning calorimetry and sorption calorimetry. Partial molar enthalpy of mixing of water in the glassy state is strongly exothermic, which gives rise to a positive temperature dependence of the water activity. The changes of the free energy of the protein induced by the hydration stabilize the denatured form of lysozyme with respect to the native form.

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  • 45.
    Kocherbitov, Vitaly
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Music, Denis
    Malmö University, Faculty of Technology and Society (TS), Department of Materials Science and Applied Mathematics (MTM). Malmö University, Biofilms Research Center for Biointerfaces.
    Veryazov, Valera
    Computational Chemistry, Kemicentrum, Lund University, P.O. Box 124, SE-22100 Lund, Sweden.
    Hydrogen bonding in glassy trehalose-water system: Insights from density functional theory and molecular dynamics simulations.2024In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 160, no 8, article id 084504Article in journal (Refereed)
    Abstract [en]

    We report a detailed density functional theory and molecular dynamics study of hydrogen bonding between trehalose and water, with a special emphasis on interactions in the amorphous solid state. For comparison, water-water interactions in water dimers and tetramers are evaluated using quantum calculations. The results show that the hydrogen bonding energy is dependent not only on the geometry (bond length and angle) but also on the local environment of the hydrogen bond. This is seen in quantum calculations of complexes in vacuum as well as in amorphous solid states with periodic boundary conditions. The temperature-induced glass transition in the trehalose-water system was studied using molecular dynamics simulations with varying cooling and heating rates. The obtained parameters of the glass transition are in good agreement with the experiments. Moreover, the dehydration of trehalose in the glassy state was investigated through a gradual dehydration with multiple small steps under isothermal conditions. From these simulations, the values of water sorption energy at different temperatures were obtained. The partial molar enthalpy of mixing of water value of -18 kJ/mol found in calorimetric experiments was accurately reproduced in these simulations. These findings are discussed in light of the hydrogen bonding data in the system. We conclude that the observed exothermic effect is due to different responses of liquid and glassy matrices to perturbations associated with the addition or removal of water molecules.

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  • 46.
    Kocherbitov, Vitaly
    et al.
    Malmö högskola, Faculty of Health and Society (HS).
    Ulvenlund, Stefan
    Kober, Maria
    Jarring, Kjell
    Arnebrant, Thomas
    Malmö högskola, Faculty of Health and Society (HS).
    Hydration of microcrystalline cellulose and milled cellulose studied by sorption calorimetry.2008In: Phys. Chem. B., Vol. 112, no 12, p. 3728-3734Article in journal (Refereed)
    Abstract [en]

    The hydration of two different polymorphs of microcrystalline cellulose (cellulose I and II), as well as the hydration of amorphous cellulose was studied using water sorption calorimetry, gravimetric water vapor sorption, nitrogen sorption, and X-ray powder diffraction. Amorphous cellulose was prepared by means of ball-milling of microcrystalline cellulose (MCC). Whereas X-ray data showed the untreated MCC to consist of cellulose I, the amorphous cellulose was found to recrystallize into cellulose II after contact with water or water vapor at relative humidities (RHs) above 90%. Sorption isotherms show an increase of water sorption in the sequence cellulose I < cellulose II < amorphous cellulose. The enthalpy of water sorption becomes more exothermic in the same sequence. The specific area of cellulose is dramatically higher when calculated from the water adsorption than when calculated from nitrogen adsorption. A proposed mechanism of water sorption by MCC implies the adsorption of water molecules at solid-solid interfaces, i.e., between neighboring microfibrils, which explains the observed difference between water and nitrogen. The Brunauer-Emmett- Teller (BET) model is therefore not appropriate for the description of the hydration of cellulose. Rather, the Langmuir model represents a more accurate description of water sorption by MCC at low RH. At higher RH, the water adsorption competes with capillary condensation. The thickness of microfibrils, as calculated using the fitting of the sorption isotherm of MCC with the Langmuir equation, is about 4 nm. This value compares favorably with literature data.

  • 47.
    Labecka, Nikol
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Division of Physical Chemistry, Chemistry Department, Lund University, SE-221 00 Lund, Sweden.
    Szczepanczyk, Michal
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Mojumdar, Enamul Haque
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Division of Physical Chemistry, Chemistry Department, Lund University, SE-221 00 Lund, Sweden; CR Competence AB, Box 124, 22100 Lund, Sweden.
    Sparr, Emma
    Division of Physical Chemistry, Chemistry Department, Lund University, SE-221 00 Lund, Sweden.
    Björklund, Sebastian
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Unraveling UVB effects: Catalase activity and molecular alterations in the stratum corneum.2024In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 666, p. 176-188, article id S0021-9797(24)00709-4Article in journal (Refereed)
    Abstract [en]

    AIM: Ultraviolet B (UVB) radiation can compromise the functionality of the skin barrier through various mechanisms. We hypothesize that UVB induce photochemical alterations in the components of the outermost layer of the skin, known as the stratum corneum (SC), and modulate its antioxidative defense mechanisms. Catalase is a well-known antioxidative enzyme found in the SC where it acts to scavenge reactive oxygen species. However, a detailed characterization of acute UVB exposure on the activity of native catalase in the SC is lacking. Moreover, the effects of UVB irradiation on the molecular dynamics and organization of the SC keratin and lipid components remain unclear. Thus, the aim of this work is to characterize consequences of UVB exposure on the structural and antioxidative properties of catalase, as well as on the molecular and global properties of the SC matrix surrounding the enzyme.

    EXPERIMENTS: The effect of UVB irradiation on the catalase function is investigated by chronoamperometry with a skin covered oxygen electrode, which probes the activity of native catalase in the SC matrix. Circular dichroism is used to explore changes of the catalase secondary structure, and gel electrophoresis is used to detect fragmentation of the enzyme following the UVB exposure. UVB induced alterations of the SC molecular dynamics and structural features of the SC barrier, as well as its water sorption behavior, are investigated by a complementary set of techniques, including natural abundance 13C polarization transfer solid-state NMR, wide-angle X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and dynamic vapor sorption microbalance.

    FINDINGS: The findings show that UVB exposure impairs the antioxidative function of catalase by deactivating both native catalase in the SC matrix and lyophilized catalase. However, UVB radiation does not alter the secondary structure of the catalase nor induce any observable enzyme fragmentation, which otherwise could explain deactivation of its function. NMR measurements on SC samples show a subtle increase in the molecular mobility of the terminal segments of the SC lipids, accompanied by a decrease in the mobility of lipid chain trans-gauche conformers after high doses of UVB exposure. At the same time, the NMR data suggest increased rigidity of the polypeptide backbone of the keratin filaments, while the molecular mobility of amino acid residues in random coil domains of keratin remain unaffected by UVB irradiation. The FTIR data show a consistent decrease in absorbance associated with lipid bond vibrations, relative to the main protein bands. Collectively, the NMR and FTIR data suggest a small modification in the composition of fluid and solid phases of the SC lipid and protein components after UVB exposure, unrelated to the hydration capacity of the SC tissue. To conclude, UVB deactivation of catalase is anticipated to elevate oxidative stress of the SC, which, when coupled with subtle changes in the molecular characteristics of the SC, may compromise the overall skin health and elevate the likelihood of developing skin disorders.

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  • 48.
    Lakey, Jeremy H.
    et al.
    Institute for Cell and Molecular Bioscience, Newcastle University 1 , Framlington Place, Newcastle upon Tyne NE2 4HH, United Kingdom.
    Paracini, Nicolò
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Clifton, Luke A.
    ISIS Pulsed Neutron and Muon Source, STFC Rutherford Appleton Laboratory 3 , Didcot OX11 0QX, United Kingdom.
    Exploiting neutron scattering contrast variation in biological membrane studies2022In: Biophysics Reviews, E-ISSN 2688-4089, Vol. 3, no 2Article, review/survey (Refereed)
    Abstract [en]

    Biological membranes composed of lipids and proteins are central for the function of all cells and individual components, such as proteins, that are readily studied by a range of structural approaches, including x-ray crystallography and cryo-electron microscopy. However, the study of complex molecular mixtures within the biological membrane structure and dynamics requires techniques that can study nanometer thick molecular bilayers in an aqueous environment at ambient temperature and pressure. Neutron methods, including scattering and spectroscopic approaches, are useful since they can measure structure and dynamics while also being able to penetrate sample holders and cuvettes. The structural approaches, such as small angle neutron scattering and neutron reflectometry, detect scattering caused by the difference in neutron contrast (scattering length) between different molecular components such as lipids or proteins. Usually, the bigger the contrast, the clearer the structural data, and this review uses examples from our research to illustrate how contrast can be increased to allow the structures of individual membrane components to be resolved. Most often this relies upon the use of deuterium in place of hydrogen, but we also discuss the use of magnetic contrast and other elements with useful scattering length values.  

  • 49.
    Larsson, Johan
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces. Lund Univ, Dept Chem, Phys Chem, Box 124, S-22100 Lund, Sweden.
    Williams, Ashley P.
    Monash Univ, Sch Chem, Clayton, Vic 3800, Australia..
    Wahlgren, Marie
    Lund Univ, Food Technol Nutr & Engn, Box 124, S-22100 Lund, Sweden.;Enza Biotech AB, Scheelevagen 22, S-22363 Lund, Sweden..
    Porcar, Lionel
    Inst Laue Langevin, DS LSS, 71 Ave Martyrs, F-38000 Grenoble, France..
    Ulvenlund, Stefan
    Lund Univ, Food Technol Nutr & Engn, Box 124, S-22100 Lund, Sweden.;Enza Biotech AB, Scheelevagen 22, S-22363 Lund, Sweden..
    Nylander, Tommy
    Lund Univ, Dept Chem, Phys Chem, Box 124, S-22100 Lund, Sweden.;Lund Univ, NanoLund, Lund, Sweden..
    Tabor, Rico F.
    Monash Univ, Sch Chem, Clayton, Vic 3800, Australia..
    Sanchez-Fernandez, Adrian
    Lund Univ, Food Technol Nutr & Engn, Box 124, S-22100 Lund, Sweden..
    Shear-induced nanostructural changes in micelles formed by sugar-based surfactants with varied anomeric configuration2022In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 606, p. 328-336Article in journal (Refereed)
    Abstract [en]

    Hypothesis: The self-assembly of long tail sugar-based surfactants into worm-like micelles has recently been demonstrated, and the rheological properties of such systems have been shown to be tuneable through subtle modifications of the molecular characteristics of the surfactant monomer. In particular, the anomeric configuration of the hexadecylmaltoside headgroup was shown to induce profound changes in the nanostructure and rheology of the system. The origin of such changes is hypothesised to arise from differences in the structure and relaxation of the micellar networks in the semi-dilute regime. Experiments: Here we explore the molecular background to the flow properties of the two anomers of hexadecylmaltoside (alpha- and beta-C(16)G(2)) by directly connecting their rheological behaviour to the micelle morphology. For this purpose, 1-3 plane rheo-small-angle neutron scattering measurements, using a Couette cell geometry, probed the structural changes in the micellar phase under shear. The effect of surfactant anomeric configuration, surfactant concentration, temperature and mixing ratio of the two anomers were investigated. The static micelle structure in the semi-dilute regime was determined using the polymer reference interaction site model. Findings: The segmental alignment of the micellar phase was studied under several flow conditions, showing that the shear-thinning behaviour relates to the re-arrangement of beta-C(16)G(2) worm-like micelles, whilst shorter alpha-C(16)G(2) micelles are considerably less affected by the flow. The results are rationalised in terms of micelle alignment and disruption of the entangled network, providing a detailed mechanism by which sugar-based surfactants control the rheology of the fluid. To further enable future studies, we provide the complete code for modelling micelle structure in the semi-dilute regime using the polymer reference interaction site model. (C) 2021 The Authors. Published by Elsevier Inc.

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  • 50.
    Lind, Tania K.
    et al.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Nilsson, Emelie J.
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Wyler, Benjamin
    LONZA AG, Switzerland.
    Scherer, Dieter
    LONZA AG, Switzerland.
    Skansberger, Tatyana
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Morin, Maxim
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Kocherbitov, Vitaly
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Engblom, Johan
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Effects of ethylene oxide chain length on crystallization of polysorbate 80 and its related compounds2021In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 592, p. 468-484, article id S0021-9797(21)00078-3Article in journal (Refereed)
    Abstract [en]

    As a result of the synthesis protocol polyoxyethylene sorbitan monooleate (polysorbate 80, PS80) is a highly complex mixture of compounds. PS80 was therefore separated into its main constituents, e.g. polyoxyethylene isosorbide esters and polyoxyethylene esters, as well as mono- di- and polyesters using preparative high-performance liquid chromatography. In this comprehensive study the individual components and their ethoxylation level were verified by matrix assisted laser desorption/ionization time-of-flight and their thermotropic behavior was analyzed using differential scanning calorimetry and X-ray diffraction. A distinct correlation was found between the average length of the ethylene oxide (EO) chains in the headgroup and the individual compounds' ability to crystallize. Importantly, a critical number of EO units required for crystallization of the headgroup was determined (6 EO units per chain or 24 per molecule). The investigation also revealed that the hydrocarbon tails only crystallize for polyoxyethylene sorbitan esters if saturated. PS80 is synthesized by reacting with approximately 20 mol of EO per mole of sorbitol, however, the number of EO units in the sorbitan ester in commercial PS80 products is higher than the expected 20 (5 EO units per chain). The complex behavior of all tested compounds revealed that if the amount of several of the linear by-products is reduced, the number of EO units in the chains will stay below the critical number and the product will not be able to crystallize by the EO chains.

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