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.

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.

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.

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.

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.

Dicarboxylate metallosurfactants (AASM), synthesized by mixing N-dodecyl aminomalonate, -aspartate and -glutamate with CaCl2, MnCl2 and CdCl2, were characterized by XRD, FTIR, and NMR spectroscopy. Layered structures, formed by metallosurfactants, were evidenced from differential scanning calorimetry and thermogravimetric analyses. Solvent-spread monolayer of AASM in combination with soyphosphatidylcholine (SPC) and cholesterol (CHOL) were studied using Langmuir surface balance. With increasing mole fraction of AASM mean molecular area increased and passed through maxima at ~60 mol% of AASMs, indicating molecular packing reorganization. Systems with 20 and 60 mol% AASM exhibited positive deviations from ideal behavior signifying repulsive interaction between the AASM and SPC, while synergistic interactions were established from the negative deviation at other combinations. Dynamic surface elasticity increased with increasing surface pressure signifying formation of rigid monolayer. Transition of monolayer from gaseous to liquid expanded to liquid condensed state was established by Brewster angle microscopic studies. Stability of the hybrid vesicles, formed by AASM+SPC+CHOL, was established by monitoring their size, zeta potential and polydispersity index values over 100 days. Size and spherical morphology of hybrid vesicles were confirmed by transmission electron microscopic studies. Biocompatibility of the hybrid vesicles were established by cytotoxicity studies revealing their possible applications in drug delivery and imaging.

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.

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.

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 Ų/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.

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.

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.

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.

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.

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.

Capacitive humidity sensors typically consist of interdigitated electrodes coated with a dielectric layer sensitive to varying relative humidity levels. Previous studies have investigated different polymeric materials that exhibit changes in conductivity in response to water vapor to design capacitive humidity sensors. However, lipid films like monoolein have not yet been integrated with humidity sensors, nor has the potential use of capacitive sensors for skin hydration measurements been fully explored. This study explores the application of monoolein-coated wireless capacitive sensors for assessing relative humidity and skin hydration, utilizing the sensitive dielectric properties of the monoolein-water system. This sensitivity hinges on the water absorption and release from the surrounding environment. Tested across various humidity levels and temperatures, these novel double functional sensors feature interdigitated electrodes covered with monoolein and show promising potential for wireless detection of skin hydration. The water uptake and rheological behavior of monoolein in response to humidity were evaluated using a quartz crystal microbalance with dissipation monitoring. The findings from these experiments suggest that the capacitance of the system is primarily influenced by the amount of water in the monoolein system, with the lyotropic or physical state of monoolein playing a secondary role. A proof-of-principle demonstration compared the sensor's performance under varying conditions to that of other commercially available skin hydration meters, affirming its effectiveness, reliability, and commercial viability.

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.

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.

. 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.

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.

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.

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.

Oppositely charged polymer -surfactant systems are expected to interact with formation of coacervate complexes near composition of charge -neutrality. Such behaviour is widely used in formulated products ( e.g. household and personal care), where the co -deposition of coacervates and active ingredients on various surfaces is triggered by dilution. A transition towards the use of more sustainable ingredients is currently ongoing as a response to the need of more environmentally conscious choices in production, albeit slowed down by the often more complex and not fully understood bulk and interfacial behaviour of new ingredients. In this work, mixtures of a mediumchain fatty acid (sodium decanoate) and two grades of bio-based cationic modified inulin were studied. The phase behaviour was determined in a wide composition matrix. The formation of coacervate complexes was observed for the mixture with the higher charge density polymer at a surfactant concentration of 1 - 3 wt%, close to the surfactant critical micellar concentration in pure water. Such behaviour was confirmed by DLS and SAXS data, suggesting surfactant -polymer complexation in a concentrated phase of packed micelles with a micelle -tomicelle distance of -4.5 nm. In situ ellipsometry and neutron reflectometry experiments were conducted to study the effect on surface deposition when diluting. The ellipsometry showed an adsorbed mass of -1.3 - 1.9 mg/m 2 , consistent with the deposition of a coacervate layer, and considerably higher than the neat, adsorbed polymer layer of -0.3 mg/m 2 . In the case of the neutron reflectometry experiments, dilution was performed before contact with the surface (pre -mixing), and no adsorption of coacervates was observed, but rather the adsorption of a polymer layer (0.49 - 0.85 mg/m 2 ). The different results obtained with the different techniques highlight the kinetic nature of bulk coacervate formation and deposition, and the competition between these two phenomena. Maximal deposition can be achieved if one can control this time window either by tuning the composition of the system or the experimental set-up, to mimic the conditions of a specific application.

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.

Binary mixtures of sucrose and trehalose in water were investigated using classical molecular dynamics (MD) simulations and free energy calculations. By classical MD simulations, the behavior of sugars was studied across the entire range of concentrations, from 0 to 100 wt % of water. Sugar–sugar and sugar–water affinities in diluted systems were in focus when using umbrella sampling and well-tempered metadynamics calculations. Moreover, in classical MD simulations, two approaches for system equilibration were applied: in the first, mixtures were preheated (using simulated annealing) before simulations under desired conditions, while in the second, no preliminary heating was used. It was discovered that sucrose has a stronger tendency to aggregate than trehalose, while the latter forms more hydrogen bonds with water. Below the concentration of 10 wt % of water, the number of hydrogen bonds between sugars is higher than the number of hydrogen bonds between sugars and water. The free energy calculations and hydrogen bonding analysis reveal certain dissimilarities in the hydration of oxygen-containing molecular groups. While there are noticeable differences in the hydration of various hydroxyl groups in sucrose and trehalose, all hydroxyl groups are clearly more hydrated than the ether oxygens in both sugars. Three factors contribute to the lower hydration of ether oxygens: they do not donate hydrogen bonds, they are slightly less polar than the oxygen atoms in hydroxyl groups, and they are less accessible to the solvent. Moreover, hydroxyl groups play the main role in binding water, and the geometry of trehalose is energetically preferable compared to the geometry of sucrose. Effects of preheating were demonstrated at water concentrations below 70 wt %, with more significant differences between mixtures observed at water concentrations below 40 wt %. Disaccharides bind stronger to each other and weaker with water molecules in preheated systems than in mixtures that were not preheated. The hydroxyl groups of sucrose and trehalose in preheated mixtures rotate slower than in systems that did not undergo thermal treatment. Therefore, while preheating is not necessary for liquid solutions, it is vital for the equilibration of samples in their amorphous solid state. In the experimental community, these findings are relevant for decision-making when choosing one of the disaccharides as a preservative.

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.

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.

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.

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.

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.

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.

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.

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.

Crowding effects significantly influence the phase behavior and the structural and dynamic properties of the concentrated protein mixtures present in the cytoplasm of cells or in the blood serum. This poses enormous difficulties for our theoretical understanding and our ability to predict the behavior of these systems. While the use of course grained colloid-inspired models allows us to reproduce the key physical solution properties of concentrated monodisperse solutions of individual proteins, we lack corresponding theories for complex polydisperse mixtures. Here, we test the applicability of simple mixing rules in order to predict solution properties of protein mixtures. We use binary mixtures of the well-characterized bovine eye lens proteins alpha and gamma(B) crystallin as model systems. Combining microrheology with static and dynamic scattering techniques and observations of the phase diagram for liquid-liquid phase separation, we show that reasonably accurate descriptions are possible for macroscopic and mesoscopic signatures, while information on the length scale of the individual protein size requires more information on cross-component interaction.

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.

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.

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.

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.

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.

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.

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.

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.

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. 

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.

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.

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.

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.

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.

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.

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.