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Islam T, Chesnokov ON, Oleinikov AV, Yi P. Supported Erythrocyte Membranes on Piezoelectric Sensors for Studying the Interactions with Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:17770-17781. [PMID: 38039387 DOI: 10.1021/acs.langmuir.3c02396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2023]
Abstract
Applications of nanoparticles (NPs) in nanodrugs, food additives, and cosmetics can result in the presence of nanomaterials in the human circulatory system and their attachment to red blood cells (RBCs), which may lead to cytotoxic effects. To investigate the interactions of NPs with RBC membranes (RBCm), supported erythrocyte membranes (SRBCm) were developed on piezoelectric sensors in a quartz crystal microbalance with dissipation (QCM-D) at 25 °C. A well-dispersed RBCm suspension at 1 mM NaCl and 0.2 mM NaHCO3 was obtained from whole blood and comprised colloidal membrane fragments with the average hydrodynamic diameter and zeta potential of 390 nm and -0.53 mV, respectively, at pH 7.0. The thin and rigid SRBCm was formed mainly through the deposition of RBCm fragments on the poly-l-lysine-modified crystal sensor, leading to the average frequency shift of -26.2 Hz and the low ratio of the dissipation to frequency shift (7.2 × 10-8 Hz-1). The complete coverage of SRBCm was indicated by the plateau of the frequency shift in the stage of SRBCm formation and no deposition of negatively charged 106 nm polystyrene nanoparticles (PSNPs) on the SRBCm. Atomic force microscopy and immunofluorescence microscopy images showed that RBCm aggregates with the average size of 420 nm and erythrocyte membrane proteins existed on SRBCm, respectively. The methods of determining attachment efficiencies of model positively charged NPs (i.e., hematite NPs or HemNPs) and model negatively charged NPs (i.e., PSNPs) on SRBCm were demonstrated in 1 mM NaCl solution at pH 5.1 and pH 7.0, respectively. HemNPs exhibited a favorable deposition with an attachment efficiency of 0.99 while PSNPs did not show any attachment propensity toward SRBCm.
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Affiliation(s)
- Tanaz Islam
- Department of Civil, Environmental, and Geomatics Engineering, College of Engineering & Computer Science, Florida Atlantic University, Boca Raton, Florida 33431-6496, United States
| | - Olga N Chesnokov
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida 33431-6496, United States
| | - Andrew V Oleinikov
- Department of Biomedical Science, Charles E. Schmidt College of Medicine, Florida Atlantic University, Boca Raton, Florida 33431-6496, United States
| | - Peng Yi
- Department of Civil, Environmental, and Geomatics Engineering, College of Engineering & Computer Science, Florida Atlantic University, Boca Raton, Florida 33431-6496, United States
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2
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Pereira D, Santamaria A, Pawar N, Carrascosa-Tejedor J, Sardo M, Mafra L, Guzmán E, Owen DJ, Zaccai NR, Maestro A, Marín-Montesinos I. Engineering phosphatidylinositol-4,5-bisphosphate model membranes enriched in endocytic cargo: A neutron reflectometry, AFM and QCM-D structural study. Colloids Surf B Biointerfaces 2023; 227:113341. [PMID: 37210796 DOI: 10.1016/j.colsurfb.2023.113341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Revised: 05/05/2023] [Accepted: 05/09/2023] [Indexed: 05/23/2023]
Abstract
The combination of in vitro models of biological membranes based on solid-supported lipid bilayers (SLBs) and of surface sensitive techniques, such as neutron reflectometry (NR), atomic force microscopy (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D), is well suited to provide quantitative information about molecular level interactions and lipid spatial distributions. In this work, cellular plasma membranes have been mimicked by designing complex SLB, containing phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P2) lipids as well as incorporating synthetic lipo-peptides that simulate the cytoplasmic tails of transmembrane proteins. The QCM-D results revealed that the adsorption and fusion kinetics of PtdIns4,5P2 are highly dependent of Mg2+. Additionally, it was shown that increasing concentrations of PtdIns4,5P2 leads to the formation of SLBs with higher homogeneity. The presence of PtdIns4,5P2 clusters was visualized by AFM. NR provided important insights about the structural organization of the various components within the SLB, highlighting that the leaflet symmetry of these SLBs is broken by the presence of CD4-derived cargo peptides. Finally, we foresee our study to be a starting point for more sophisticated in vitro models of biological membranes with the incorporation of inositol phospholipids and synthetic endocytic motifs.
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Affiliation(s)
- Daniel Pereira
- Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal; Large Scale Structures Group, Institut Laue-Langevin, 38042 Cedex 9, Grenoble, France
| | - Andreas Santamaria
- Large Scale Structures Group, Institut Laue-Langevin, 38042 Cedex 9, Grenoble, France; Departamento de Química Física, Universidad Complutense de Madrid, 28040, Madrid, Spain
| | - Nisha Pawar
- Centro de Fı́sica de Materiales (CSIC, UPV/EHU) - Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain
| | - Javier Carrascosa-Tejedor
- Large Scale Structures Group, Institut Laue-Langevin, 38042 Cedex 9, Grenoble, France; Division of Pharmacy and Optometry, University of Manchester, M13 9PT Manchester, UK
| | - Mariana Sardo
- Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Luís Mafra
- Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
| | - Eduardo Guzmán
- Departamento de Química Física, Universidad Complutense de Madrid, 28040, Madrid, Spain; Instituto Pluridisciplinar, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - David J Owen
- Cambridge Institute for Medical Research, University of Cambridge, CB22 7QQ Cambridge, UK
| | - Nathan R Zaccai
- Cambridge Institute for Medical Research, University of Cambridge, CB22 7QQ Cambridge, UK
| | - Armando Maestro
- Centro de Fı́sica de Materiales (CSIC, UPV/EHU) - Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; IKERBASQUE-Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain.
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3
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Paracini N, Gutfreund P, Welbourn R, Gonzalez-Martinez JF, Zhu K, Miao Y, Yepuri N, Darwish TA, Garvey C, Waldie S, Larsson J, Wolff M, Cárdenas M. Structural Characterization of Nanoparticle-Supported Lipid Bilayer Arrays by Grazing Incidence X-ray and Neutron Scattering. ACS APPLIED MATERIALS & INTERFACES 2023; 15:3772-3780. [PMID: 36625710 PMCID: PMC9880997 DOI: 10.1021/acsami.2c18956] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Arrays of nanoparticle-supported lipid bilayers (nanoSLB) are lipid-coated nanopatterned interfaces that provide a platform to study curved model biological membranes using surface-sensitive techniques. We combined scattering techniques with direct imaging, to gain access to sub-nanometer scale structural information on stable nanoparticle monolayers assembled on silicon crystals in a noncovalent manner using a Langmuir-Schaefer deposition. The structure of supported lipid bilayers formed on the nanoparticle arrays via vesicle fusion was investigated using a combination of grazing incidence X-ray and neutron scattering techniques complemented by fluorescence microscopy imaging. Ordered nanoparticle assemblies were shown to be suitable and stable substrates for the formation of curved and fluid lipid bilayers that retained lateral mobility, as shown by fluorescence recovery after photobleaching and quartz crystal microbalance measurements. Neutron reflectometry revealed the formation of high-coverage lipid bilayers around the spherical particles together with a flat lipid bilayer on the substrate below the nanoparticles. The presence of coexisting flat and curved supported lipid bilayers on the same substrate, combined with the sub-nanometer accuracy and isotopic sensitivity of grazing incidence neutron scattering, provides a promising novel approach to investigate curvature-dependent membrane phenomena on supported lipid bilayers.
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Affiliation(s)
- Nicolò Paracini
- Department
for Biomedical Science and Biofilms − Research Center for Biointerfaces,
Faculty of Health and Society, Malmö
University, 205 06Malmö, Sweden
| | | | - Rebecca Welbourn
- ISIS
Neutron & Muon Source, STFC, Rutherford
Appleton Laboratory, Harwell, OxfordshireOX11 0QX, U.K.
| | - Juan Francisco Gonzalez-Martinez
- Department
for Biomedical Science and Biofilms − Research Center for Biointerfaces,
Faculty of Health and Society, Malmö
University, 205 06Malmö, Sweden
| | - Kexin Zhu
- School
of Biological Sciences, Nanyang Technological
University, 639798Singapore
| | - Yansong Miao
- School
of Biological Sciences, Nanyang Technological
University, 639798Singapore
| | - Nageshwar Yepuri
- National
Deuteration Facility, Australian Nuclear
Science and Technology Organization (ANSTO), Lucas Heights, NSW2234, Australia
| | - Tamim A. Darwish
- National
Deuteration Facility, Australian Nuclear
Science and Technology Organization (ANSTO), Lucas Heights, NSW2234, Australia
| | - Christopher Garvey
- Heinz
Maier-Leibnitz
Zentrum (MLZ), Technische Universität
München, Lichtenbergstraβe 1, 85748Garching, Germany
| | - Sarah Waldie
- Department
for Biomedical Science and Biofilms − Research Center for Biointerfaces,
Faculty of Health and Society, Malmö
University, 205 06Malmö, Sweden
| | - Johan Larsson
- Department
for Biomedical Science and Biofilms − Research Center for Biointerfaces,
Faculty of Health and Society, Malmö
University, 205 06Malmö, Sweden
| | - Max Wolff
- Department
of Physics and Astronomy, Uppsala University, Box 516, 751 20Uppsala, Sweden
| | - Marité Cárdenas
- Department
for Biomedical Science and Biofilms − Research Center for Biointerfaces,
Faculty of Health and Society, Malmö
University, 205 06Malmö, Sweden
- School
of Biological Sciences, Nanyang Technological
University, 639798Singapore
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4
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Santamaria A, Carrascosa-Tejedor J, Guzmán E, Zaccai NR, Maestro A. Unravelling the orientation of the inositol-biphosphate ring and its dependence on phosphatidylinositol 4,5-bisphosphate cluster formation in model membranes. J Colloid Interface Sci 2023; 629:785-795. [PMID: 36195018 DOI: 10.1016/j.jcis.2022.09.095] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 09/03/2022] [Accepted: 09/18/2022] [Indexed: 10/14/2022]
Abstract
HYPOTHESIS Inositol phospholipids are well known to form clusters in the cytoplasmic leaflet of the plasma membrane that are responsible for the interaction and recruitment of proteins involved in key biological processes like endocytosis, ion channel activation and secondary messenger production. Although their phosphorylated inositol ring headgroup plays an important role in protein binding, its orientation with respect to the plane of the membrane and its lateral packing density has not been previously described experimentally. EXPERIMENTS Here, we study phosphatidylinositol 4,5-bisphosphate (PIP2) planar model membranes in the form of Langmuir monolayers by surface pressure-area isotherms, Brewster angle microscopy and neutron reflectometry to elucidate the relation between lateral (in-plane) and perpendicular (out-of-plane) molecular organization of PIP2. FINDINGS Different surface areas were explored through monolayer compression, allowing us to correlate the formation of transient PIP2 clusters with the change in orientation of the inositol-biphosphate headgroup, which was experimentally determined by neutron reflectometry.
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Affiliation(s)
- Andreas Santamaria
- Large Scale Structures Group, Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, Cedex 9, France; Departamento de Química-Física, Facultad de Ciencias Químicas, Universidad Complutense, Ciudad Universitaria s/n, 28040 Madrid, Spain
| | - Javier Carrascosa-Tejedor
- Large Scale Structures Group, Institut Laue-Langevin, 71 Avenue des Martyrs, 38042 Grenoble, Cedex 9, France; Division of Pharmacy and Optometry, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Eduardo Guzmán
- Departamento de Química-Física, Facultad de Ciencias Químicas, Universidad Complutense, Ciudad Universitaria s/n, 28040 Madrid, Spain; Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII 1, 28040 Madrid, Spain.
| | - Nathan R Zaccai
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB22 7QQ, United Kingdom.
| | - Armando Maestro
- Centro de Fı́sica de Materiales (CSIC, UPV/EHU) - Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, E-20018 San Sebastián, Spain; IKERBASQUE-Basque Foundation for Science, Plaza Euskadi 5, Bilbao 48009, Spain.
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5
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Motlaq VF, Adlmann FA, Hernández VA, Vorobiev A, Wolff M, Bergström LM. Dissolution mechanism of supported phospholipid bilayer in the presence of amphiphilic drug investigated by neutron reflectometry and quartz crystal microbalance with dissipation monitoring. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183976. [PMID: 35662645 DOI: 10.1016/j.bbamem.2022.183976] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 05/12/2022] [Accepted: 05/26/2022] [Indexed: 06/15/2023]
Abstract
The influence and interaction of the ionizable amphiphilic drug amitriptyline hydrochloride (AMT) on a 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) phospholipid bilayer supported on a silica surface have been investigated using a combination of neutron reflectometry and quartz crystal microbalance with dissipation monitoring. Adding AMT solutions with concentrations 3, 12, and 50 mM leaves the lipid bilayer mainly intact and we observe most of the AMT molecules attached to the head-group region of the outer bilayer leaflet. Virtually no AMT penetrates into the hydrophilic head-group region of the inner leaflet close to the silica surface. By adding 200 mM AMT solution, the lipid bilayer dissolved entirely, indicating a threshold concentration for the solubilization of the bilayer by AMT. The observed threshold concentration is consistent with the observation that various bilayer structures abruptly transform into mixed AMT-DOPC micelles beyond a certain AMT-DOPC composition. Based on our experimental observations, we suggest that the penetration of drug into the phospholipid bilayer, and subsequent solubilization of the membrane, follows a two-step mechanism with the outer leaflet being removed prior to the inner leaflet.
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Affiliation(s)
- V Forooqi Motlaq
- Department of Medicinal Chemistry, Uppsala University, P.O. Box 547, 751 23 Uppsala, Sweden; Department of Pharmacy, Uppsala University, P.O. Box 580, 75123 Uppsala, Sweden
| | - F A Adlmann
- Department of Medicinal Chemistry, Uppsala University, P.O. Box 547, 751 23 Uppsala, Sweden; Department of Pharmacy, Uppsala University, P.O. Box 580, 75123 Uppsala, Sweden
| | - V Agmo Hernández
- Department of Medicinal Chemistry, Uppsala University, P.O. Box 547, 751 23 Uppsala, Sweden
| | - A Vorobiev
- Division for Materials Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
| | - M Wolff
- Division for Materials Physics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
| | - L M Bergström
- Department of Medicinal Chemistry, Uppsala University, P.O. Box 547, 751 23 Uppsala, Sweden; Department of Pharmacy, Uppsala University, P.O. Box 580, 75123 Uppsala, Sweden.
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6
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Formation of a Fully Anionic Supported Lipid Bilayer to Model Bacterial Inner Membrane for QCM-D Studies. MEMBRANES 2022; 12:membranes12060558. [PMID: 35736265 PMCID: PMC9229009 DOI: 10.3390/membranes12060558] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 05/18/2022] [Accepted: 05/25/2022] [Indexed: 12/04/2022]
Abstract
Supported lipid bilayers (SLBs) on quartz crystals are employed as versatile model systems for studying cell membrane behavior with the use of the highly sensitive technique of quartz crystal microbalance with dissipation monitoring (QCM-D). Since the lipids constituting cell membranes vary from predominantly zwitterionic lipids in mammalian cells to predominantly anionic lipids in the inner membrane of Gram-positive bacteria, the ability to create SLBs of different lipid compositions is essential for representing different cell membranes. While methods to generate stable zwitterionic SLBs and zwitterionic-dominant mixed zwitterionic–anionic SLBs on quartz crystals have been well established, there are no reports of being able to form predominantly or fully anionic SLBs. We describe here a method for forming entirely anionic SLBs by treating the quartz crystal with cationic (3-aminopropyl) trimethoxysilane (APTMS). The formation of the anionic SLB was tracked using QCM-D by monitoring the adsorption of anionic lipid vesicles to a quartz surface and subsequent bilayer formation. Anionic egg L-α-phosphatidylglycerol (PG) vesicles adsorbed on the surface-treated quartz crystal, but did not undergo the vesicle-to-bilayer transition to create an SLB. However, when PG was mixed with 10–40 mole% 1-palmitoyl-2-hydroxy-sn-glycero-3-phospho-(1′-rac-glycerol) (LPG), the mixed vesicles led to the formation of stable SLBs. The dynamics of SLB formation monitored by QCM-D showed that while SLB formation by zwitterionic lipids followed a two-step process of vesicle adsorption followed by the breakdown of the adsorbed vesicles (which in turn is a result of multiple events) to create the SLB, the PG/LPG mixed vesicles ruptured immediately on contacting the quartz surface resulting in a one-step process of SLB formation. The QCM-D data also enabled the quantitative characterization of the SLB by allowing estimation of the lipid surface density as well as the thickness of the hydrophobic region of the SLB. These fully anionic SLBs are valuable model systems to conduct QCM-D studies of the interactions of extraneous substances such as antimicrobial peptides and nanoparticles with Gram-positive bacterial membranes.
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7
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Lipid bilayer degradation induced by SARS-CoV-2 spike protein as revealed by neutron reflectometry. Sci Rep 2021; 11:14867. [PMID: 34290262 PMCID: PMC8295359 DOI: 10.1038/s41598-021-93996-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2021] [Accepted: 06/29/2021] [Indexed: 12/19/2022] Open
Abstract
SARS-CoV-2 spike proteins are responsible for the membrane fusion event, which allows the virus to enter the host cell and cause infection. This process starts with the binding of the spike extramembrane domain to the angiotensin-converting enzyme 2 (ACE2), a membrane receptor highly abundant in the lungs. In this study, the extramembrane domain of SARS-CoV-2 Spike (sSpike) was injected on model membranes formed by supported lipid bilayers in presence and absence of the soluble part of receptor ACE2 (sACE2), and the structural features were studied at sub-nanometer level by neutron reflection. In all cases the presence of the protein produced a remarkable degradation of the lipid bilayer. Indeed, both for membranes from synthetic and natural lipids, a significant reduction of the surface coverage was observed. Quartz crystal microbalance measurements showed that lipid extraction starts immediately after sSpike protein injection. All measurements indicate that the presence of proteins induces the removal of membrane lipids, both in the presence and in the absence of ACE2, suggesting that sSpike molecules strongly associate with lipids, and strip them away from the bilayer, via a non-specific interaction. A cooperative effect of sACE2 and sSpike on lipid extraction was also observed.
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8
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Neutron reflectometry study of the interface between two immiscible electrolyte solutions: Effects of electrolyte concentration, applied electric field, and lipid adsorption. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.138336] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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9
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Waldie S, Sebastiani F, Moulin M, Del Giudice R, Paracini N, Roosen-Runge F, Gerelli Y, Prevost S, Voss JC, Darwish TA, Yepuri N, Pichler H, Maric S, Forsyth VT, Haertlein M, Cárdenas M. ApoE and ApoE Nascent-Like HDL Particles at Model Cellular Membranes: Effect of Protein Isoform and Membrane Composition. Front Chem 2021; 9:630152. [PMID: 33996741 PMCID: PMC8117676 DOI: 10.3389/fchem.2021.630152] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 03/30/2021] [Indexed: 11/13/2022] Open
Abstract
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.
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Affiliation(s)
- Sarah Waldie
- Department of Biomedical Science and Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, Sweden.,Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France
| | - Federica Sebastiani
- Department of Biomedical Science and Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, Sweden
| | - Martine Moulin
- Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France
| | - Rita Del Giudice
- Department of Biomedical Science and Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, Sweden
| | - Nicolò Paracini
- Department of Biomedical Science and Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, Sweden
| | - Felix Roosen-Runge
- Department of Biomedical Science and Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, Sweden
| | - Yuri Gerelli
- Institut Laue-Langevin, Grenoble, France.,Department of Life and Environmental Sciences, Marche Polytechnic University, Ancona, Italy
| | | | - John C Voss
- Department of Biochemistry and Molecular Medicine, University of California, Davis, Davis, CA, United States
| | - Tamim A Darwish
- National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
| | - Nageshwar Yepuri
- National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
| | - Harald Pichler
- Austrian Centre of Industrial Biotechnology, Graz, Austria.,Graz University of Technology, Institute of Molecular Biotechnology, NAWI Graz, BioTechMed Graz, Graz, Austria
| | | | - V Trevor Forsyth
- Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France.,Faculty of Natural Sciences, Keele University, Staffordshire, United Kingdom
| | - Michael Haertlein
- Institut Laue-Langevin, Grenoble, France.,Partnership for Structural Biology (PSB), Grenoble, France
| | - Marité Cárdenas
- Department of Biomedical Science and Biofilms-Research Center for Biointerfaces, Malmö University, Malmö, Sweden
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10
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Luchini A, Corucci G, Chaithanya Batchu K, Laux V, Haertlein M, Cristiglio V, Fragneto G. Structural Characterization of Natural Yeast Phosphatidylcholine and Bacterial Phosphatidylglycerol Lipid Multilayers by Neutron Diffraction. Front Chem 2021; 9:628186. [PMID: 33968895 PMCID: PMC8104085 DOI: 10.3389/fchem.2021.628186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/01/2021] [Indexed: 01/08/2023] Open
Abstract
Eukaryotic and prokaryotic cell membranes are difficult to characterize directly with biophysical methods. Membrane model systems, that include fewer molecular species, are therefore often used to reproduce their fundamental chemical and physical properties. In this context, natural lipid mixtures directly extracted from cells are a valuable resource to produce advanced models of biological membranes for biophysical investigations and for the development of drug testing platforms. In this study we focused on single phospholipid classes, i.e. Pichia pastoris phosphatidylcholine (PC) and Escherichia coli phosphatidylglycerol (PG) lipids. These lipids were characterized by a different distribution of their respective acyl chain lengths and number of unsaturations. We produced both hydrogenous and deuterated lipid mixtures. Neutron diffraction experiments at different relative humidities were performed to characterize multilayers from these lipids and investigate the impact of the acyl chain composition on the structural organization. The novelty of this work resides in the use of natural extracts with a single class head-group and a mixture of chain compositions coming from yeast or bacterial cells. The characterization of the PC and PG multilayers showed that, as a consequence of the heterogeneity of their acyl chain composition, different lamellar phases are formed.
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Affiliation(s)
| | - Giacomo Corucci
- Institut Laue Langevin, Grenoble, France.,Université Grenoble Alpes, Ecole Doctorale de Physique, Saint-Martin-d'Héres, France
| | | | | | | | | | - Giovanna Fragneto
- Institut Laue Langevin, Grenoble, France.,Université Grenoble Alpes, Ecole Doctorale de Physique, Saint-Martin-d'Héres, France
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11
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Luchini A, Vitiello G. Mimicking the Mammalian Plasma Membrane: An Overview of Lipid Membrane Models for Biophysical Studies. Biomimetics (Basel) 2020; 6:biomimetics6010003. [PMID: 33396534 PMCID: PMC7838988 DOI: 10.3390/biomimetics6010003] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 12/23/2020] [Accepted: 12/28/2020] [Indexed: 02/07/2023] Open
Abstract
Cell membranes are very complex biological systems including a large variety of lipids and proteins. Therefore, they are difficult to extract and directly investigate with biophysical methods. For many decades, the characterization of simpler biomimetic lipid membranes, which contain only a few lipid species, provided important physico-chemical information on the most abundant lipid species in cell membranes. These studies described physical and chemical properties that are most likely similar to those of real cell membranes. Indeed, biomimetic lipid membranes can be easily prepared in the lab and are compatible with multiple biophysical techniques. Lipid phase transitions, the bilayer structure, the impact of cholesterol on the structure and dynamics of lipid bilayers, and the selective recognition of target lipids by proteins, peptides, and drugs are all examples of the detailed information about cell membranes obtained by the investigation of biomimetic lipid membranes. This review focuses specifically on the advances that were achieved during the last decade in the field of biomimetic lipid membranes mimicking the mammalian plasma membrane. In particular, we provide a description of the most common types of lipid membrane models used for biophysical characterization, i.e., lipid membranes in solution and on surfaces, as well as recent examples of their applications for the investigation of protein-lipid and drug-lipid interactions. Altogether, promising directions for future developments of biomimetic lipid membranes are the further implementation of natural lipid mixtures for the development of more biologically relevant lipid membranes, as well as the development of sample preparation protocols that enable the incorporation of membrane proteins in the biomimetic lipid membranes.
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Affiliation(s)
- Alessandra Luchini
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark;
| | - Giuseppe Vitiello
- Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Piazzale Tecchio 80, 80125 Naples, Italy
- CSGI-Center for Colloid and Surface Science, via della Lastruccia 3, 50019 Sesto Fiorentino (Florence), Italy
- Correspondence:
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12
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Luchini A, Sebastiani F, Tidemand FG, Batchu KC, Campana M, Fragneto G, Cárdenas M, Arleth L. Peptide discs as precursors of biologically relevant supported lipid bilayers. J Colloid Interface Sci 2020; 585:376-385. [PMID: 33307306 DOI: 10.1016/j.jcis.2020.11.086] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 11/19/2020] [Accepted: 11/23/2020] [Indexed: 12/19/2022]
Abstract
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.
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Affiliation(s)
- Alessandra Luchini
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark.
| | - Federica Sebastiani
- Biofilms Research Center for Biointerfaces and Department of Biomedical Science, Faculty of Health and Society, Malmö University, Per Albin Hanssons Väg 35, 21432 Malmö, Sweden
| | | | | | - Mario Campana
- ISIS-STFC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom
| | - Giovanna Fragneto
- Institut Laue Langevin, 71 avenue des Martyrs, 38000 Grenoble, France
| | - Marité Cárdenas
- Biofilms Research Center for Biointerfaces and Department of Biomedical Science, Faculty of Health and Society, Malmö University, Per Albin Hanssons Väg 35, 21432 Malmö, Sweden
| | - Lise Arleth
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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13
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Ridolfi A, Caselli L, Montis C, Mangiapia G, Berti D, Brucale M, Valle F. Gold nanoparticles interacting with synthetic lipid rafts: an AFM investigation. J Microsc 2020; 280:194-203. [PMID: 32432336 DOI: 10.1111/jmi.12910] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/12/2020] [Accepted: 05/14/2020] [Indexed: 12/30/2022]
Abstract
Inorganic nanoparticles (NPs) represent promising examples of engineered nanomaterials, providing interesting biomedical solutions in several fields, like therapeutics and diagnostics. Despite the extensive number of investigations motivated by their remarkable potential for nanomedicinal applications, the interactions of NPs with biological interfaces are still poorly understood. The effect of NPs on living organisms is mediated by biological barriers, such as the cell plasma membrane, whose lateral heterogeneity is thought to play a prominent role in NPs adsorption and uptake pathways. In particular, biological membranes feature the presence of rafts, that is segregated lipid micro and/or nanodomains in the so-called liquid ordered phase (Lo ), immiscible with the surrounding liquid disordered phase (Ld ). Rafts are involved in various biological functions and act as sites for the selective adsorption of materials on the membrane. Indeed, the thickness mismatch present along their boundaries generates energetically favourable conditions for the adsorption of NPs. Despite its clear implications in NPs internalisation processes and cytotoxicity, a direct proof of the selective adsorption of NPs along the rafts' boundaries is still missing to date. Here we use multicomponent supported lipid bilayers (SLBs) as reliable synthetic models, reproducing the nanometric lateral heterogeneity of cell membranes. After being characterised by atomic force microscopy (AFM) and neutron reflectivity (NR), multidomain SLBs are challenged by prototypical inorganic nanoparticles, that is citrated gold nanoparticles (AuNPs), under simplified and highly controlled conditions. By exploiting AFM, we demonstrate that AuNPs preferentially target lipid phase boundaries as adsorption sites. The herein reported study consolidates and extends the fundamental knowledge on NPs-membrane interactions, which constitute a key aspect to consider when designing NPs-related biomedical applications. LAY DESCRIPTION: Inorganic nanoparticles (NPs) represent promising examples of engineered nanomaterials, offering interesting biomedical solutions in multiple fields like therapeutics and diagnostics. Despite being extensively investigated due to their remarkable potential for nanomedicinal applications, the interaction of NPs with biological systems is in several cases still poorly understood. The interaction of NPs with living organisms is mediated by biological barriers, such as the cell plasma membrane. Supported lipid bilayers (SLBs) represent suitable synthetic membrane models for studying the physicochemical properties of natural interfaces and their interaction with inorganic nanomaterials under simplified and controlled conditions. Recently, multicomponent SLBs were developed in order to mimic the lateral heterogeneity of most biological membranes. In particular, biological membranes feature the presence of rafts, that is segregated lipid micro and/or nanodomains, enriched in cholesterol, sphingomyelin, saturated glycerophospholipids and glycosphingolipids: these lipids segregate in the so-called liquid-ordered phase (Lo ), characterised by a high molecular packing degree, which promotes the phase separation from the surrounding liquid-crystalline (disordered, Ld ) phase, where the intermolecular mobility is increased. Rafts are thought to participate in the formation and targeting of nano-sized biogenic lipid vesicles and are also actively involved in multiple membrane processes. Indeed, Lo -Ld phase boundaries represent high energy areas, providing active sites for the preferential adsorption of external material. The selective adsorption of NPs along the phase boundaries of rafted membranes has been theorised and indirectly probed by different research groups; however, a direct proof of this phenomenon is still missing to date. We herein exploit atomic force microscopy (AFM) to directly visualise the preferential adsorption of gold nanoparticles (AuNPs) along the phase boundaries of multicomponent SLBs (previously characterised by neutron reflectivity), obtained from synthetic vesicles containing both an Ld and an Lo phase. The quantitative localisation and morphometry of AuNPs adsorbed on the SLB reveal important information on their interaction with the lipid matrix and directly prove the already theorised differential NPs-lipid interaction at the phase boundaries. The presented results could help the development of future NP-based applications, involving NPs adsorption on membranes with nanoscale phase segregations.
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Affiliation(s)
- Andrea Ridolfi
- Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Florence, Italy.,Consiglio Nazionale delle Ricerche, Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), Bologna, Italy.,Dipartimento di Chimica 'Ugo Schiff', Università degli Studi di Firenze, Florence, Italy
| | - Lucrezia Caselli
- Dipartimento di Chimica 'Ugo Schiff', Università degli Studi di Firenze, Florence, Italy
| | - Costanza Montis
- Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Florence, Italy.,Dipartimento di Chimica 'Ugo Schiff', Università degli Studi di Firenze, Florence, Italy
| | - Gaetano Mangiapia
- GEMS am Heinz Maier-Leibnitz Zentrum (MLZ), Helmholtz-Zentrum Geesthacht GmbH, Garching, Germany
| | - Debora Berti
- Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Florence, Italy.,Dipartimento di Chimica 'Ugo Schiff', Università degli Studi di Firenze, Florence, Italy
| | - Marco Brucale
- Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Florence, Italy.,Consiglio Nazionale delle Ricerche, Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), Bologna, Italy
| | - Francesco Valle
- Consorzio Interuniversitario per lo Sviluppo dei Sistemi a Grande Interfase (CSGI), Florence, Italy.,Consiglio Nazionale delle Ricerche, Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), Bologna, Italy
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14
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Clifton LA, Campbell RA, Sebastiani F, Campos-Terán J, Gonzalez-Martinez JF, Björklund S, Sotres J, Cárdenas M. Design and use of model membranes to study biomolecular interactions using complementary surface-sensitive techniques. Adv Colloid Interface Sci 2020; 277:102118. [PMID: 32044469 DOI: 10.1016/j.cis.2020.102118] [Citation(s) in RCA: 44] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 01/24/2020] [Accepted: 01/29/2020] [Indexed: 01/07/2023]
Abstract
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.
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Affiliation(s)
- Luke A Clifton
- ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 OQX, United Kingdom
| | - Richard A Campbell
- Division of Pharmacy and Optometry, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Federica Sebastiani
- Department of Biomedical Science and Biofilms - Research Center for Biointerfaces, Malmö University, 20506 Malmö, Sweden
| | - José Campos-Terán
- Departamento de Procesos y Tecnología, Universidad Autónoma Metropolitana, Unidad Cuajimalpa, Av. Vasco de Quiroga 4871, Col. Santa Fe, Delegación Cuajimalpa de Morelos, 05348, Mexico; Lund Institute of advanced Neutron and X-ray Science, Lund University, Scheelevägen 19, 223 70 Lund, Sweden
| | - Juan F Gonzalez-Martinez
- Department of Biomedical Science and Biofilms - Research Center for Biointerfaces, Malmö University, 20506 Malmö, Sweden
| | - Sebastian Björklund
- Department of Biomedical Science and Biofilms - Research Center for Biointerfaces, Malmö University, 20506 Malmö, Sweden
| | - Javier Sotres
- Department of Biomedical Science and Biofilms - Research Center for Biointerfaces, Malmö University, 20506 Malmö, Sweden
| | - Marité Cárdenas
- Department of Biomedical Science and Biofilms - Research Center for Biointerfaces, Malmö University, 20506 Malmö, Sweden.
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Protocol for Investigating the Interactions Between Intrinsically Disordered Proteins and Membranes by Neutron Reflectometry. Methods Mol Biol 2020; 2141:569-584. [PMID: 32696378 DOI: 10.1007/978-1-0716-0524-0_29] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Several intrinsically disordered proteins (IDPs) exhibit high affinity for lipid membranes. Among the different biophysical methods to probe protein-lipid interaction, neutron reflectometry (NR) can provide direct and structural detailed information on the location of the IDP with respect to the membrane. Supported lipid bilayers are commonly used as cell membrane models in such experiments. NR measurements can be collected on the supported lipid bilayer before and after the interaction with the IDP to characterize whether the protein molecules are mainly located on the membrane surface (interaction with the lipid headgroups), are penetrating into the hydrophobic region of the membrane (interaction with the lipid acyl chains), or are not interacting at all with the membrane. The lipid composition of the supported lipid bilayer can easily be tuned; hence the NR experiments can be designed to investigate selective IDP-lipid interactions.This chapter will describe the fundamental steps for performing an NR experiment and the subsequent data analysis aimed at characterizing IDP-lipid bilayer interactions. The specific case of an intrinsically disordered region (IDR) from the membrane protein Na+/H+ exchanger isoform 1 (NHE1) will be used as an example, but the same protocol can be easily adapted to other IDPs.
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16
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Wilson KA, Wang L, MacDermott-Opeskin H, O'Mara ML. The Fats of Life: Using Computational Chemistry to Characterise the Eukaryotic Cell Membrane. Aust J Chem 2020. [DOI: 10.1071/ch19353] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Our current knowledge of the structural dynamics and complexity of lipid bilayers is still developing. Computational techniques, especially molecular dynamics simulations, have increased our understanding significantly as they allow us to model functions that cannot currently be experimentally resolved. Here we review available computational tools and techniques, the role of the major lipid species, insights gained into lipid bilayer structure and function from molecular dynamics simulations, and recent progress towards the computational modelling of the physiological complexity of eukaryotic lipid bilayers.
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17
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Luchini A, Tidemand FG, Johansen NT, Campana M, Sotres J, Ploug M, Cárdenas M, Arleth L. Peptide Disc Mediated Control of Membrane Protein Orientation in Supported Lipid Bilayers for Surface-Sensitive Investigations. Anal Chem 2019; 92:1081-1088. [DOI: 10.1021/acs.analchem.9b04125] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Alessandra Luchini
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | | | | | - Mario Campana
- ISIS-STFC, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, United Kingdom
| | - Javier Sotres
- Biofilms Research Center for Biointerfaces and Department of Biomedical Science, Faculty of Health and Society, Malmö University, Per Albin Hanssons Väg 35, 214 32 Malmö, Sweden
| | - Michael Ploug
- Biotech Research and Innovation Center, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark
- Finsen Laboratory, Rigshospitalet, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark
| | - Marité Cárdenas
- Biofilms Research Center for Biointerfaces and Department of Biomedical Science, Faculty of Health and Society, Malmö University, Per Albin Hanssons Väg 35, 214 32 Malmö, Sweden
| | - Lise Arleth
- Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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18
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Lakey JH. Recent advances in neutron reflectivity studies of biological membranes. Curr Opin Colloid Interface Sci 2019. [DOI: 10.1016/j.cocis.2019.02.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Lind TK, Skoda MWA, Cárdenas M. Formation and Characterization of Supported Lipid Bilayers Composed of Phosphatidylethanolamine and Phosphatidylglycerol by Vesicle Fusion, a Simple but Relevant Model for Bacterial Membranes. ACS OMEGA 2019; 4:10687-10694. [PMID: 31460166 PMCID: PMC6648305 DOI: 10.1021/acsomega.9b01075] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 06/06/2019] [Indexed: 05/06/2023]
Abstract
Supported lipid bilayers (SLBs) are simple and robust biomimics with controlled lipid composition that are widely used as models of both mammalian and bacterial membranes. However, the lipids typically used for SLB formation poorly resemble those of bacterial cell membranes due to the lack of available protocols to form SLBs using mixtures of lipids relevant for bacteria such as phosphatidylethanolamine (PE) and phosphatidylglycerol (PG). Although a few reports have been published recently on the formation of SLBs from Escherichia coli lipid extracts, a detailed understanding of these systems is challenging due to the complexity of the lipid composition in such natural extracts. Here, we present for the first time a simple and reliable protocol optimized to form high-quality SLBs using mixtures of PE and PG at compositions relevant for Gram-negative membranes. We show using neutron reflection and quartz microbalance not only that Ca2+ ions and temperature are key parameters for successful bilayer deposition but also that mass transfer to the surface is a limiting factor. Continuous flow of the lipid suspension is thus crucial for obtaining full SLB coverage. We furthermore characterize the resulting bilayers and report structural parameters, for the first time for PE and PG mixtures, which are in good agreement with those reported earlier for pure POPE vesicles. With this protocol in place, more suitable and reproducible studies can be conducted to understand biomolecular processes occurring at cell membranes, for example, for testing specificities and to unravel the mechanism of interaction of antimicrobial peptides.
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Affiliation(s)
- Tania Kjellerup Lind
- Biofilms Research
Centre for Biointerfaces and Biomedical Science Department, Faculty
of Health and Society, Malmo University, Malmo 20506, Sweden
| | | | - Marité Cárdenas
- Biofilms Research
Centre for Biointerfaces and Biomedical Science Department, Faculty
of Health and Society, Malmo University, Malmo 20506, Sweden
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20
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The Production of Matchout-Deuterated Cholesterol and the Study of Bilayer-Cholesterol Interactions. Sci Rep 2019; 9:5118. [PMID: 30914734 PMCID: PMC6435723 DOI: 10.1038/s41598-019-41439-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 03/07/2019] [Indexed: 02/04/2023] Open
Abstract
The deuteration of biomolecules provides advanced opportunities for neutron scattering studies. For low resolution studies using techniques such as small-angle neutron scattering and neutron reflection, the level of deuteration of a sample can be varied to match the scattering length density of a specific D2O/H2O solvent mixture. This can be of major value in structural studies where specific regions of a complex system can be highlighted, and others rendered invisible. This is especially useful in analyses of the structure and dynamics of membrane components. In mammalian membranes, the presence of cholesterol is crucial in modulating the properties of lipids and in their interaction with proteins. Here, a protocol is described for the production of partially deuterated cholesterol which has a neutron scattering length density that matches that of 100% D2O solvent (hereby named matchout cholesterol). The level of deuteration was determined by mass spectrometry and nuclear magnetic resonance. The cholesterol match-point was verified experimentally using small angle neutron scattering. The matchout cholesterol was used to investigate the incorporation of cholesterol in various phosphatidylcholine supported lipid bilayers by neutron reflectometry. The study included both saturated and unsaturated lipids, as well as lipids with varying chain lengths. It was found that cholesterol is distributed asymmetrically within the bilayer, positioned closer to the headgroups of the lipids than to the middle of the tail core, regardless of the phosphatidylcholine species.
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