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Sebastiani, FedericaORCID iD iconorcid.org/0000-0002-7405-6125
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Luchini, A., Tidemand, F. G., Johansen, N. T., Sebastiani, F., Corucci, G., Fragneto, G., . . . Arleth, L. (2022). Dark peptide discs for the investigation of membrane proteins in supported lipid bilayers: the case of synaptobrevin 2 (VAMP2). Nanoscale Advances, 10(17)
Öppna denna publikation i ny flik eller fönster >>Dark peptide discs for the investigation of membrane proteins in supported lipid bilayers: the case of synaptobrevin 2 (VAMP2)
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2022 (Engelska)Ingår i: Nanoscale Advances, E-ISSN 2516-0230, Vol. 10, nr 17Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Supported lipid bilayers (SLBs) are commonly used as model systems mimicking biological membranes. Recently, we reported a new method to produce SLBs with incorporated membrane proteins, which is based on the application of peptide discs [Luchini et al., Analytical Chemistry, 2020, 92, 1081-1088]. Peptide discs are small discoidal particles composed of a lipid core and an outer belt of self-assembled 18A peptides. SLBs including membrane proteins can be formed by depositing the peptide discs on a solid support and subsequently removing the peptide by buffer rinsing. Here, we introduce a new variant of the 18A peptide, named dark peptide (d18A). d18A exhibits UV absorption at 214 nm, whereas the absorption at 280 nm is negligible. This improves sample preparation as it enables a direct quantification of the membrane protein concentration in the peptide discs by measuring UV absorption at 280 nm. We describe the application of the peptide discs prepared with d18A (dark peptide discs) to produce SLBs with a membrane protein, synaptobrevin 2 (VAMP2). The collected data showed the successful formation of SLBs with high surface coverage and incorporation of VAMP2 in a single orientation with the extramembrane domain exposed towards the bulk solvent. Compared to 18A, we found that d18A was more efficiently removed from the SLB. Our data confirmed the structural organisation of VAMP2 as including both alpha-helical and beta-sheet secondary structure. We further verified the orientation of VAMP2 in the SLBs by characterising the binding of VAMP2 with alpha-synuclein. These results point at the produced SLBs as relevant membrane models for biophysical studies as well as nanostructured biomaterials.

Ort, förlag, år, upplaga, sidor
Royal Society of Chemistry, 2022
Nationell ämneskategori
Biokemi och molekylärbiologi
Identifikatorer
urn:nbn:se:mau:diva-55391 (URN)10.1039/d2na00384h (DOI)000855805500001 ()36341300 (PubMedID)2-s2.0-85139258329 (Scopus ID)
Tillgänglig från: 2022-10-17 Skapad: 2022-10-17 Senast uppdaterad: 2023-10-09Bibliografiskt granskad
Sebastiani, F., Campbell, R. A. & Pfrang, C. (2022). Night-time oxidation at the air-water interface: co-surfactant effects in binary mixtures. Environmental Science: Atmospheres (6), 1324-1337
Öppna denna publikation i ny flik eller fönster >>Night-time oxidation at the air-water interface: co-surfactant effects in binary mixtures
2022 (Engelska)Ingår i: Environmental Science: Atmospheres, E-ISSN 2634-3606, nr 6, s. 1324-1337Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The ageing of organic-coated aqueous aerosols at night is investigated by reacting NO<INF>3</INF> with binary surfactant mixtures floating on water. The surfactants are oleic acid (OA), methyl oleate (MO) and stearic acid (SA). Deuterated surfactants mixed with hydrogenous surfactants were studied using neutron reflectometry to determine the reaction kinetics of organic two-component monolayers with NO<INF>3</INF> at the air-water interface for the first time. We measured the rate coefficients for OA monolayers, mixed with hydrogenous co-surfactant MO or SA to be (3 +/- 1) x 10<SUP>-8</SUP> cm<SUP>2</SUP> per molecule per s or (3.6 +/- 0.9) x 10<SUP>-8</SUP> cm<SUP>2</SUP> per molecule per s and MO monolayers mixed with hydrogenous co-surfactant OA or SA to be (0.7 +/- 0.4) x 10<SUP>-8</SUP> cm<SUP>2</SUP> per molecule per s or (3 +/- 1) x 10<SUP>-8</SUP> cm<SUP>2</SUP> per molecule per s. The initial desorption lifetimes of NO<INF>3</INF>, tau<INF>d,NO<INF>3,1</INF></INF>, were 8 +/- 3 ns, 14 +/- 4 ns, 12 +/- 3 ns and 21 +/- 10 ns. The approximately doubled desorption lifetime for MO-SA compared to the other mixtures is consistent with a more accessible double bond associated with the larger area per molecule of MO in the presence of SA facilitating NO<INF>3</INF> attack. The significantly slower reactive loss of MO-OA compared to a MO monolayer demonstrates that multi-component surfactant mixtures need to be studied in addition to single-component monolayers. Such a retarded decay would cause the residence time to change from ca. 4 to 22 minutes associated with increased transport distances of surfactant species together with any other pollutants that may be protected underneath the surfactant film.

Ort, förlag, år, upplaga, sidor
Royal Society of Chemistry, 2022
Nationell ämneskategori
Kemi
Identifikatorer
urn:nbn:se:mau:diva-55392 (URN)10.1039/d2ea00056c (DOI)000859651300001 ()
Tillgänglig från: 2022-10-19 Skapad: 2022-10-19 Senast uppdaterad: 2023-10-05Bibliografiskt granskad
Waldie, S., Sebastiani, F., Moulin, M., Del Giudice, R., Paracini, N., Roosen-Runge, F., . . . Cárdenas, M. (2021). ApoE and ApoE Nascent-Like HDL Particles at Model Cellular Membranes: Effect of Protein Isoform and Membrane Composition. Frontiers in Chemistry, 9, Article ID 630152.
Öppna denna publikation i ny flik eller fönster >>ApoE and ApoE Nascent-Like HDL Particles at Model Cellular Membranes: Effect of Protein Isoform and Membrane Composition
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2021 (Engelska)Ingår i: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 9, artikel-id 630152Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Apolipoprotein E (ApoE), an important mediator of lipid transportation in plasma and the nervous system, plays a large role in diseases such as atherosclerosis and Alzheimer's. The major allele variants ApoE3 and ApoE4 differ only by one amino acid. However, this difference has major consequences for the physiological behaviour of each variant. In this paper, we follow (i) the initial interaction of lipid-free ApoE variants with model membranes as a function of lipid saturation, (ii) the formation of reconstituted High-Density Lipoprotein-like particles (rHDL) and their structural characterisation, and (iii) the rHDL ability to exchange lipids with model membranes made of saturated lipids in the presence and absence of cholesterol [1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC) with and without 20 mol% cholesterol]. Our neutron reflection results demonstrate that the protein variants interact differently with the model membranes, adopting different protein conformations. Moreover, the ApoE3 structure at the model membrane is sensitive to the level of lipid unsaturation. Small-angle neutron scattering shows that the ApoE containing lipid particles form elliptical disc-like structures, similar in shape but larger than nascent or discoidal HDL based on Apolipoprotein A1 (ApoA1). Neutron reflection shows that ApoE-rHDL do not remove cholesterol but rather exchange saturated lipids, as occurs in the brain. In contrast, ApoA1-containing particles remove and exchange lipids to a greater extent as occurs elsewhere in the body.

Ort, förlag, år, upplaga, sidor
Frontiers Media S.A., 2021
Nyckelord
ApoE isoforms, lipid exchange, reconstituted HDL, model membranes, neutron reflection, small-angle neutron scattering
Nationell ämneskategori
Biokemi och molekylärbiologi
Identifikatorer
urn:nbn:se:mau:diva-42335 (URN)10.3389/fchem.2021.630152 (DOI)000649795200001 ()33996741 (PubMedID)2-s2.0-85105930481 (Scopus ID)
Tillgänglig från: 2021-05-26 Skapad: 2021-05-26 Senast uppdaterad: 2023-10-17Bibliografiskt granskad
Sebastiani, F., Yanez Arteta, M., Lerche, M., Porcar, L., Lang, C., Bragg, R. A., . . . Cárdenas, M. (2021). Apolipoprotein E Binding Drives Structural and Compositional Rearrangement of mRNA-Containing Lipid Nanoparticles. ACS Nano, 15(4), 6709-6722
Öppna denna publikation i ny flik eller fönster >>Apolipoprotein E Binding Drives Structural and Compositional Rearrangement of mRNA-Containing Lipid Nanoparticles
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2021 (Engelska)Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 15, nr 4, s. 6709-6722Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Emerging therapeutic treatments based on the production of proteins by delivering mRNA have become increasingly important in recent times. While lipid nanoparticles (LNPs) are approved vehicles for small interfering RNA delivery, there are still challenges to use this formulation for mRNA delivery. LNPs are typically a mixture of a cationic lipid, distearoylphosphatidylcholine (DSPC), cholesterol, and a PEG-lipid. The structural characterization of mRNA-containing LNPs (mRNA-LNPs) is crucial for a full understanding of the way in which they function, but this information alone is not enough to predict their fate upon entering the bloodstream. The biodistribution and cellular uptake of LNPs are affected by their surface composition as well as by the extracellular proteins present at the site of LNP administration, e.g., apolipoproteinE (ApoE). ApoE, being responsible for fat transport in the body, plays a key role in the LNP’s plasma circulation time. In this work, we use small-angle neutron scattering, together with selective lipid, cholesterol, and solvent deuteration, to elucidate the structure of the LNP and the distribution of the lipid components in the absence and the presence of ApoE. While DSPC and cholesterol are found to be enriched at the surface of the LNPs in buffer, binding of ApoE induces a redistribution of the lipids at the shell and the core, which also impacts the LNP internal structure, causing release of mRNA. The rearrangement of LNP components upon ApoE incubation is discussed in terms of potential relevance to LNP endosomal escape. 

Ort, förlag, år, upplaga, sidor
American Chemical Society (ACS), 2021
Nyckelord
ApoE, lipid nanoparticles, mRNA delivery, protein corona, small-angle scattering
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:mau:diva-62966 (URN)10.1021/acsnano.0c10064 (DOI)000645436800066 ()33754708 (PubMedID)2-s2.0-85104076829 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet, 2014-3981Vetenskapsrådet, 2018-03990Vetenskapsrådet, 2018-0483EU, Horisont 2020, 654000EU, Horisont 2020, 731019
Tillgänglig från: 2023-10-05 Skapad: 2023-10-05 Senast uppdaterad: 2023-10-05Bibliografiskt granskad
Luchini, A., Sebastiani, F., Tidemand, F. G., Batchu, K. C., Campana, M., Fragneto, G., . . . Arleth, L. (2021). Peptide discs as precursors of biologically relevant supported lipid bilayers. Journal of Colloid and Interface Science, 585, 376-385, Article ID S0021-9797(20)31605-2.
Öppna denna publikation i ny flik eller fönster >>Peptide discs as precursors of biologically relevant supported lipid bilayers
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2021 (Engelska)Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 585, s. 376-385, artikel-id S0021-9797(20)31605-2Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Supported lipid bilayers (SLBs) are commonly used to investigate the structure and dynamics of biological membranes. Vesicle fusion is a widely exploited method to produce SLBs. However, this process becomes less favoured when the vesicles contain complex lipid mixtures, e.g. natural lipid extracts. In these cases, it is often necessary to change experimental parameters, such as temperature, to unphysiological values to trigger the SLB formation. This may induce lipid degradation and is also not compatible with including membrane proteins or other biomolecules into the bilayers. Here, we show that the peptide discs, ~10 nm discoidal lipid bilayers stabilized in solution by a self-assembled 18A peptide belt, can be used as precursors for SLBs. The characterizations by means of neutron reflectometry and attenuated total reflectance-FTIR spectroscopy show that SLBs were successfully formed both from synthetic lipid mixtures (surface coverage 90-95%) and from natural lipid mixtures (surface coverage ~85%). Traces of 18A peptide (below 0.02 M ratio) left at the support surface after the bilayer formation do not affect the SLB structure. Altogether, we demonstrate that peptide disc formation of SLBs is much faster than the SLB formation by vesicle fusion and without the need of altering any experimental variable from physiologically relevant values.

Ort, förlag, år, upplaga, sidor
Elsevier, 2021
Nyckelord
ATR-FTIR, Neutron reflectometry, Peptide discs, Supported lipid bilayers
Nationell ämneskategori
Biofysik
Identifikatorer
urn:nbn:se:mau:diva-37777 (URN)10.1016/j.jcis.2020.11.086 (DOI)000604569200010 ()33307306 (PubMedID)2-s2.0-85097582761 (Scopus ID)
Tillgänglig från: 2021-01-05 Skapad: 2021-01-05 Senast uppdaterad: 2023-10-24Bibliografiskt granskad
Sebastiani, F., Yanez Arteta, M., Lindfors, L. & Cárdenas, M. (2021). Screening of the binding affinity of serum proteins to lipid nanoparticles in a cell free environment. Journal of Colloid and Interface Science, 610, 766-774, Article ID S0021-9797(21)02028-2.
Öppna denna publikation i ny flik eller fönster >>Screening of the binding affinity of serum proteins to lipid nanoparticles in a cell free environment
2021 (Engelska)Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 610, s. 766-774, artikel-id S0021-9797(21)02028-2Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Lipid nanoparticles (LNPs) are promising drug and gene carriers. Upon intravenous administration, LNPs' experience different degree of cellular uptake depending on their formulation. Currently, in vitro and in vivo studies are the gold standard for assessing the fate of nano carriers once administered, but they are time consuming and expensive. In this work, we propose a time and cost-effective method to screen a wide range of LNP formulations and select the most promising candidates for in vitro and in vivo studies. Two different approaches were explored to investigate the binding affinity between LNPs and serum proteins using sensor functionalisation with either protein specific antibody or PEG specific antibody. The first approach allowed to identify the presence of a specific protein in the protein corona of lipid particles (reconstituted and native high-density lipoproteins (rHDL and HDL), and low-density lipoproteins LDL); while the second one provided a versatile platform for the immobilisation of pegylated-particles in order to follow the interaction with serum proteins and hence predict the composition of LNP protein corona. Sensing was done using Quartz Crystal Microbalance with Dissipation (QCM-D) but the approach is extendable to other surface sensing techniques such as Surface Plasmon Resonance (SPR) or ellipsometry.

Ort, förlag, år, upplaga, sidor
Elsevier, 2021
Nyckelord
Binding affinity, Lipid-based nanoparticles, Protein corona, QCM-D
Nationell ämneskategori
Biokemi och molekylärbiologi
Identifikatorer
urn:nbn:se:mau:diva-47447 (URN)10.1016/j.jcis.2021.11.117 (DOI)000750676700002 ()34848062 (PubMedID)2-s2.0-85123575197 (Scopus ID)
Tillgänglig från: 2021-12-10 Skapad: 2021-12-10 Senast uppdaterad: 2024-02-05Bibliografiskt granskad
Clifton, L. A., Campbell, R. A., Sebastiani, F., Campos-Terán, J., Gonzalez-Martinez, J. F., Björklund, S., . . . Cárdenas, M. (2020). Design and use of model membranes to study biomolecular interactions using complementary surface-sensitive techniques.. Advances in Colloid and Interface Science, 277, Article ID 102118.
Öppna denna publikation i ny flik eller fönster >>Design and use of model membranes to study biomolecular interactions using complementary surface-sensitive techniques.
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2020 (Engelska)Ingår i: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 277, artikel-id 102118Artikel i tidskrift (Refereegranskat) Published
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.

Ort, förlag, år, upplaga, sidor
Elsevier, 2020
Nyckelord
Antimicrobial peptides., Biomembranes, Biomolecular interactions, Lipids, Model membrane., Surface-sensitive techniques
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:mau:diva-14237 (URN)10.1016/j.cis.2020.102118 (DOI)000521512600007 ()32044469 (PubMedID)2-s2.0-85078986446 (Scopus ID)
Tillgänglig från: 2020-03-31 Skapad: 2020-03-31 Senast uppdaterad: 2024-02-05Bibliografiskt granskad
Waldie, S., Sebastiani, F., Browning, K., Maric, S., Lind, T. K., Yepuri, N., . . . Cárdenas, M. (2020). Lipoprotein ability to exchange and remove lipids from model membranes as a function of fatty acid saturation and presence of cholesterol.. Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids, 1865(10), Article ID 158769.
Öppna denna publikation i ny flik eller fönster >>Lipoprotein ability to exchange and remove lipids from model membranes as a function of fatty acid saturation and presence of cholesterol.
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2020 (Engelska)Ingår i: Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids, ISSN 1388-1981, E-ISSN 1879-2618, Vol. 1865, nr 10, artikel-id 158769Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Lipoproteins play a central role in the development of atherosclerosis. High and low-density lipoproteins (HDL and LDL), known as 'good' and 'bad' cholesterol, respectively, remove and/or deposit lipids into the artery wall. Hence, insight into lipid exchange processes between lipoproteins and cell membranes is of particular importance in understanding the onset and development of cardiovascular disease. In order to elucidate the impact of phospholipid tail saturation and the presence of cholesterol in cell membranes on these processes, neutron reflection was employed in the present investigation to follow lipid exchange with both HDL and LDL against model membranes. Mirroring clinical risk factors for the development of atherosclerosis, lower exchange was observed in the presence of cholesterol, as well as for an unsaturated phospholipid, compared to faster exchange when using a fully saturated phospholipid. These results highlight the importance of membrane composition on the interaction with lipoproteins, chiefly the saturation level of the lipids and presence of cholesterol, and provide novel insight into factors of importance for build-up and reversibility of atherosclerotic plaque. In addition, the correlation between the results and well-established clinical risk factors suggests that the approach taken can be employed also for understanding a broader set of risk factors including, e.g., effects of triglycerides and oxidative stress, as well as local effects of drugs on atherosclerotic plaque formation.

Ort, förlag, år, upplaga, sidor
Elsevier, 2020
Nyckelord
Cholesterol, Lipid removal, Lipoproteins, Neutron reflection, Saturated fats
Nationell ämneskategori
Biokemi och molekylärbiologi
Identifikatorer
urn:nbn:se:mau:diva-18012 (URN)10.1016/j.bbalip.2020.158769 (DOI)000563386500006 ()32712249 (PubMedID)2-s2.0-85088787543 (Scopus ID)
Tillgänglig från: 2020-08-17 Skapad: 2020-08-17 Senast uppdaterad: 2024-02-05Bibliografiskt granskad
Tummino, A., Toscano, J., Sebastiani, F., Noskov, B. A., Varga, I. & Campbell, R. A. (2018). Effects of Aggregate Charge and Subphase Ionic Strength on the Properties of Spread Polyelectrolyte/Surfactant Films at the Air/Water Interface under Static and Dynamic Conditions (ed.). Langmuir, 34(6), 2312-2323
Öppna denna publikation i ny flik eller fönster >>Effects of Aggregate Charge and Subphase Ionic Strength on the Properties of Spread Polyelectrolyte/Surfactant Films at the Air/Water Interface under Static and Dynamic Conditions
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2018 (Engelska)Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, nr 6, s. 2312-2323Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We demonstrate the ability to tune the formation of extended structures in films of poly(sodium styrenesulfonate)/dodecyltrimethylammonium bromide at the air/water interface through control over the charge/structure of aggregates as well as the ionic strength of the subphase. Our methodology to prepare loaded polyelectrolyte/surfactant films from self-assembled liquid crystalline aggregates exploits their fast dissociation and Marangoni spreading of material upon contact with an aqueous subphase. This process is proposed as a potential new route to prepare cheap biocompatible films for transfer applications. We show that films spread on water from Marangoni swollen aggregates of low/negative charge have 1:1 charge Spreading binding and can be compressed only to a monolayer, beyond which material is lost to the bulk. For films spread on water from compact aggregates of positive charge, however, extended structures of the two components are created upon spreading or upon compression of the film beyond a monolayer. The application of ellipsometry, Brewster angle microscopy, and neutron reflectometry as well as measurements of surface pressure isotherms allow us to reason that formation of extended structures is activated by aggregates embedded in the film. The situation upon spreading on 0.1 M NaCl is different as there is a high concentration of small ions that stabilize loops of the polyelectrolyte upon film compression, yet extended structures of both components are only transient. Analogy of the controlled formation of extended structures in fluid monolayers is made to reservoir dynamics in lung surfactant. The work opens up the possibility to control such film dynamics in related systems through the rational design of particles in the future.

Ort, förlag, år, upplaga, sidor
American Chemical Society (ACS), 2018
Nyckelord
Chemistry, Multidisciplinary, Chemistry, Physical, Materials Science, Multidisciplinary
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:mau:diva-4011 (URN)10.1021/acs.langmuir.7b03960 (DOI)000425474800010 ()29323919 (PubMedID)2-s2.0-85041959354 (Scopus ID)27251 (Lokalt ID)27251 (Arkivnummer)27251 (OAI)
Tillgänglig från: 2020-02-28 Skapad: 2020-02-28 Senast uppdaterad: 2024-02-05Bibliografiskt granskad
Sebastiani, F., Campbell, R. A., Rastogi, K. & Pfrang, C. (2018). Nighttime oxidation of surfactants at the air-water interface: effects of chain length, head group and saturation (ed.). Atmospheric Chemistry And Physics, 18(5), 3249-3268
Öppna denna publikation i ny flik eller fönster >>Nighttime oxidation of surfactants at the air-water interface: effects of chain length, head group and saturation
2018 (Engelska)Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 18, nr 5, s. 3249-3268Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Reactions of the key atmospheric nighttime oxidant NO3 with organic monolayers at the air-water interface are used as proxies for the ageing of organic-coated aqueous aerosols. The surfactant molecules chosen for this study are oleic acid (OA), palmitoleic acid (POA), methyl oleate ( MO) and stearic acid ( SA) to investigate the effects of chain length, head group and degree of unsaturation on the reaction kinetics and products formed. Fully and partially deuterated surfactants were studied using neutron reflectometry (NR) to determine the reaction kinetics of organic monolayers with NO3 at the air-water interface for the first time. Kinetic modelling allowed us to determine the rate coefficients for the oxidation of OA, POA and MO monolayers to be (2.8 +/- 0.7) x 10(-8), (2.4 +/- 0.5) x 10(-8) and (3.3 +/- 0.6) x 10(-8) cm(2) molecule(-1) s(-1) for fitted initial desorption lifetimes of NO3 at the closely packed organic monolayers, tau(d), NO3, 1, of 8.1 +/- 4.0, 16 +/- 4.0 and 8.1 +/- 3.0 ns, respectively. The approximately doubled desorption lifetime found in the best fit for POA compared to OA and MO is consistent with a more accessible double bond associated with the shorter alkyl chain of POA facilitating initial NO3 attack at the double bond in a closely packed monolayer. The corresponding uptake coefficients for OA, POA and MO were found to be (2.1 +/- 0.5) x 10(-3), (1.7 +/- 0.3) x 10(-3) and (2.1 +/- 0.4) x 10(-3), respectively. For the much slower NO3-initiated oxidation of the saturated surfactant SA we estimated a loss rate of approximately (5 +/- 1) x 10(-12) cm(2) molecule(-1) s(-1), which we consider to be an upper limit for the reactive loss, and estimated an uptake coefficient of ca, (5 +/- 1) x 10(-7). Our investigations demonstrate that NO3 will contribute substantially to the processing of unsaturated surfactants at the air-water interface during nighttime given its reactivity is ca. 2 orders of magnitude higher than that of O-3. Furthermore, the relative contributions of NO3 and O-3 to the oxidative losses vary massively between species that are closely related in structure: NO3 reacts ca. 400 times faster than O-3 with the common model surfactant oleic acid, but only ca. 60 times faster with its methyl ester MO. It is therefore necessary to perform a case-by-case assessment of the relative contributions of the different degradation routes for any specific surfactant. The overall impact of NO3 on the fate of saturated surfactants is slightly less clear given the lack of prior kinetic data for comparison, but NO3 is likely to contribute significantly to the loss of saturated species and dominate their loss during nighttime. The retention of the organic character at the air-water interface differs fundamentally between the different surfactant species: the fatty acids studied (OA and POA) form products with a yield of similar to 20% that are stable at the interface while NO3=initiated oxidation of the methyl ester MO rapidly and effectively removes the organic character (<= 3% surface-active products). The film-forming potential of reaction products in real aerosol is thus likely to depend on the relative proportions of saturated and unsaturated surfactants as well as the head group properties. Atmospheric lifetimes of unsaturated species are much longer than those determined with respect to their reactions at the air-water interface, so they must be protected from oxidative attack, for example, by incorporation into a complex aerosol matrix or in mixed surface films with yet unexplored kinetic behaviour.

Ort, förlag, år, upplaga, sidor
European Geosciences Union (EGU), 2018
Nyckelord
Meteorology & Atmospheric Sciences
Nationell ämneskategori
Naturvetenskap
Identifikatorer
urn:nbn:se:mau:diva-4672 (URN)10.5194/acp-18-3249-2018 (DOI)000426918000001 ()26631 (Lokalt ID)26631 (Arkivnummer)26631 (OAI)
Tillgänglig från: 2020-02-28 Skapad: 2020-02-28 Senast uppdaterad: 2023-10-05Bibliografiskt granskad
Projekt
Lipidnanopartikel – proteininteraktioner: Formuleringsoptimering för bättre terapeutisk effekt; Malmö universitet, Biofilms Research Center for Biointerfaces
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-7405-6125

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