1
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Pandey Y, Ingold A, Kumar N, Zenobi R. Nanoscale visualization of phase separation in binary supported lipid monolayer using tip-enhanced Raman spectroscopy. NANOSCALE 2024; 16:10578-10583. [PMID: 38767416 PMCID: PMC11154864 DOI: 10.1039/d4nr00816b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 05/05/2024] [Indexed: 05/22/2024]
Abstract
Supported lipid membranes are an important model system to study the phase separation behavior at the nanoscale. However, the conventional nanoanalytical tools often fail to provide reliable chemical characterization of the phase separated domains in a non-destructive and label-free manner. This study demonstrates the application of scanning tunneling microscopy-based tip-enhanced Raman spectroscopy (TERS) to study the nanoscale phase separation in supported d62-DPPC : DOPC lipid monolayers. Hyperspectral TERS imaging successfully revealed a clear segregation of the d62-DPPC-rich and DOPC-rich domains. Interestingly, nanoscale deposits of d62-DPPC were observed inside the DOPC-rich domains and vice versa. High-resolution TERS imaging also revealed the presence of a 40-120 nm wide interfacial region between the d62-DPPC-rich and DOPC-rich domains signifying a smooth transition rather than a sharp boundary between them. The novel insights obtained in this study demonstrate the effectiveness of TERS in studying binary lipid monolayers at the nanoscale.
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Affiliation(s)
- Yashashwa Pandey
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
| | - Andrea Ingold
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
| | - Naresh Kumar
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
| | - Renato Zenobi
- Department of Chemistry and Applied Biosciences, ETH Zurich, Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
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2
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Bryant SJ, Garvey CJ, Darwish TA, Georgii R, Bryant G. Molecular interactions with bilayer membrane stacks using neutron and X-ray diffraction. Adv Colloid Interface Sci 2024; 326:103134. [PMID: 38518550 DOI: 10.1016/j.cis.2024.103134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/14/2024] [Accepted: 03/14/2024] [Indexed: 03/24/2024]
Abstract
Lamellar unit cell reconstruction from neutron and X-ray diffraction data provides information about the disposition and position of molecules and molecular segments with respect to the bilayer. When supplemented with the judicious use of molecular deuteration, the technique probes the molecular interactions and conformations within the bilayer membrane and the water layer which constitute the crystallographic unit cell. The perspective is model independent, and potentially, with a higher degree of resolution than is available with other techniques. In the case of neutron diffraction the measurement consists of carefully normalised diffracted intensity under conditions of contrast variation of the water layer. The subsequent Fourier reconstruction of the unit cell is made using the phase information from variation of peak intensities with contrast. Although the phase problem is not as easily solved for the corresponding X-ray measurements, an intuitive approach can often suffice. Here we discuss the two complimentary techniques as probes of scattering length density profiles of a bilayer, and how such a perspective provides information about the location and orientation of molecules within or between lipid bilayers. Within the basic paradigm of lamellar phases this method has provided, for example, detailed insights into the location and interaction of cryoprotectants and stress proteins, of the mechanisms of actions of viral proteins, antimicrobial compounds and drugs, and the underlying structure of the stratum corneum. In this paper we review these techniques and provide examples of the systems that have been examined. We finish with a future outlook on the use of these techniques to improve our understanding of the interactions of membranes with biomolecules.
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Affiliation(s)
- Saffron J Bryant
- School of Science, College of STEM, RMIT University, Melbourne, Australia
| | - Christopher J Garvey
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany
| | - Tamim A Darwish
- National Deuteration Facility, Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia; Faculty of Science and Technology, University of Canberra, ACT 2617, Australia
| | - Robert Georgii
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany
| | - Gary Bryant
- School of Science, College of STEM, RMIT University, Melbourne, Australia.
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3
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Grusky DS, Bhattacharya A, Boxer SG. Secondary Ion Mass Spectrometry of Single Giant Unilamellar Vesicles Reveals Compositional Variability. J Am Chem Soc 2023; 145:27521-27530. [PMID: 38056605 PMCID: PMC10904076 DOI: 10.1021/jacs.3c09039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Giant unilamellar vesicles (GUVs) are a widely used model system to interrogate lipid phase behavior, study biomembrane mechanics, reconstitute membrane proteins, and provide a chassis for synthetic cells. It is generally assumed that the composition of individual GUVs is the same as the nominal stock composition; however, there may be significant compositional variability between individual GUVs. Although this compositional heterogeneity likely impacts phase behavior, the function and incorporation of membrane proteins, and the encapsulation of biochemical reactions, it has yet to be directly quantified. To assess heterogeneity, we use secondary ion mass spectrometry (SIMS) to probe the composition of individual GUVs using non-perturbing isotopic labels. Both 13C- and 2H-labeled lipids are incorporated into a ternary mixture, which is then used to produce GUVs via gentle hydration or electroformation. Simultaneous detection of seven different ion species via SIMS allows for the concentration of 13C- and 2H-labeled lipids in single GUVs to be quantified using calibration curves, which correlate ion intensity to composition. Additionally, the relative concentration of 13C- and 2H-labeled lipids is assessed for each GUV via the ion ratio 2H-/13C-, which is highly sensitive to compositional differences between individual GUVs and circumvents the need for calibration by using standards. Both quantification methods suggest that gentle hydration produces GUVs with greater compositional variability than those formed by electroformation. However, both gentle hydration and electroformation display standard deviations in composition (n = 30 GUVs) on the order of 1-4 mol %, consistent with variability seen in previous indirect measurements.
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Affiliation(s)
- Dashiel S Grusky
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Ahanjit Bhattacharya
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
| | - Steven G Boxer
- Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States
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4
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Schwörer F, Trapp M, Silvi L, Gutfreund P, Steitz R, Dahint R. Location of Polyelectrolytes in Swollen Lipid Oligobilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:14958-14968. [PMID: 37815275 DOI: 10.1021/acs.langmuir.3c01792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/11/2023]
Abstract
Osteoarthritis is caused by degeneration of the cartilage, which covers the bone ends of the joints and is decorated with an oligolamellar phospholipid (PL) bilayer. The gap between the bone ends is filled with synovial fluid mainly containing hyaluronic acid (HA). HA and PLs are supposed to reduce friction and protect the cartilage from wear in joint movement. However, a detailed understanding of the molecular mechanisms of joint lubrication is still missing. Previously, we found that aqueous solutions of HA and poly(allylamine hydrochloride) (PAH), the latter serving as a polymeric analogue to HA, adsorb onto the headgroups of surface-bound 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) oligobilayers and significantly enhance their stability with respect to shear forces, typically occurring in joint movement. We now investigated the precise location of PAH chains across the lipid films in neutron reflectivity measurements, as bridging of the oligobilayers by polyelectrolytes (PEs) might be the cause for their improved mechanical stability. In a first set of experiments, we used hydrogenated PAH and chain-deuterated DMPC (DMPC-d54) to improve the contrast between the lipids and potentially intruding PAH. However, due to difficulties in distinguishing between incorporation of water and PAH, penetration into the lipid chain region could hardly be proven quantitatively. Therefore, we designed a more elaborate experiment based on mixed films of DMPC-d54 and hydrogenated DMPC, which is insensitive to water penetration into the films. Beside facilitating a detailed structural characterization of the oligolamellar system, this elaborate approach showed that PAH adsorbs to the DMPC heads and penetrates the lipid tail strata. No PAH was found in the lipid head strata, which excludes bridging of several lipid bilayers by the PE chains. The data are consistent with the assumption that PAH bridges are formed between the headgroups of two adjacent bilayers and contribute to the enhanced mechanical stability.
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Affiliation(s)
- Felicitas Schwörer
- Applied Physical Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 253, Heidelberg 69120, Germany
| | - Marcus Trapp
- Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin 14109, Germany
| | - Luca Silvi
- Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin 14109, Germany
| | | | - Roland Steitz
- Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin 14109, Germany
| | - Reiner Dahint
- Applied Physical Chemistry, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 253, Heidelberg 69120, Germany
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5
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Garvey CJ, Bryant SJ, Elbourne A, Hunt T, Kent B, Kreuzer M, Strobl M, Steitz R, Bryant G. Phase separation in a ternary DPPC/DOPC/POPC system with reducing hydration. J Colloid Interface Sci 2023; 638:719-732. [PMID: 36774881 DOI: 10.1016/j.jcis.2023.01.145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/10/2023] [Accepted: 01/31/2023] [Indexed: 02/05/2023]
Abstract
The maintenance of plasma membrane structure is vital for the viability of cells. Disruption of this structure can lead to cell death. One important example is the macroscopic phase separation observed during dehydration associated with desiccation and freezing, often leading to loss of permeability and cell death. It has previously been shown that the hybrid lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) can act as a line-active component in ternary lipid systems, inhibiting macroscopic phase separation and stabilising membrane microdomains in lipid vesicles [1]. The domain size is found to decrease with increasing POPC concentration until complete mixing is observed. However, no such studies have been carried out at reduced hydration. To examine if this phase separation is unique to vesicles in excess water, we have conducted studies on several binary and ternary model membrane systems at both reduced hydration ("powder" type samples and oriented membrane stacks) and in excess water (supported lipid bilayers) at 0.2 mol fraction POPC, in the range where microdomain stabilisation is reported. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) are used to map phase transition temperatures, with X-ray and neutron scattering providing details of the changes in lipid packing and phase information within these boundaries. Atomic force microscopy (AFM) is used to image bilayers on a substrate in excess water. In all cases, macroscopic phase separation was observed rather than microdomain formation at this molar ratio. Thus POPC does not stabilise microdomains under these conditions, regardless of the type of model membrane, hydration or temperature. Thus we conclude that the driving force for separation under these conditions overcomes any linactant effects of the hybrid lipid.
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Affiliation(s)
- Christopher J Garvey
- Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany.
| | | | - Aaron Elbourne
- School of Science, RMIT University, Melbourne, Australia
| | - Taavi Hunt
- School of Science, RMIT University, Melbourne, Australia
| | - Ben Kent
- Centre for Advanced Macromolecular Design, School of Chemistry, The University of New South Wales, Sydney 2052, Australia; Institute for Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin, Germany
| | - Martin Kreuzer
- Institute for Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin, Germany; ALBA Synchrotron, Barcelona, Spain
| | - Markus Strobl
- Institute for Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin, Germany; Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, 5232 Villigen, Switzerland
| | - Roland Steitz
- Institute for Soft Matter and Functional Materials, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz 1, Berlin, Germany
| | - Gary Bryant
- School of Science, RMIT University, Melbourne, Australia.
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6
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Kinnun JJ, Scott HL, Bolmatov D, Collier CP, Charlton TR, Katsaras J. Biophysical studies of lipid nanodomains using different physical characterization techniques. Biophys J 2023; 122:931-949. [PMID: 36698312 PMCID: PMC10111277 DOI: 10.1016/j.bpj.2023.01.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2022] [Revised: 01/12/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023] Open
Abstract
For the past 50 years, evidence for the existence of functional lipid domains has been steadily accumulating. Although the notion of functional lipid domains, also known as "lipid rafts," is now widely accepted, this was not always the case. This ambiguity surrounding lipid domains could be partly attributed to the fact that they are highly dynamic, nanoscopic structures. Since most commonly used techniques are sensitive to microscale structural features, it is therefore, not surprising that it took some time to reach a consensus regarding their existence. In this review article, we will discuss studies that have used techniques that are inherently sensitive to nanoscopic structural features (i.e., neutron scatting, nuclear magnetic resonance, and Förster resonance energy transfer). We will also mention techniques that may be of use in the future (i.e., cryoelectron microscopy, droplet interface bilayers, inelastic x-ray scattering, and neutron reflectometry), which can further our understanding of the different and unique physicochemical properties of nanoscopic lipid domains.
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Affiliation(s)
- Jacob J Kinnun
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
| | - Haden L Scott
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Dima Bolmatov
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee
| | - C Patrick Collier
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Timothy R Charlton
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - John Katsaras
- Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee; Labs and Soft Matter Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
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7
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Stengel D, Thai R, Li Y, Peters NM, Holland GP. Biphasic nature of lipid bilayers assembled on silica nanoparticles and evidence for an interdigitated phase. SOFT MATTER 2023; 19:1882-1889. [PMID: 36799359 DOI: 10.1039/d2sm01517j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Functionalizing silica nanoparticles with a lipid bilayer shell is a common first step in fabricating drug delivery and biosensing devices that are further decorated with other biomolecules for a range of nanoscience applications and therapeutics. Although the molecular structure and dynamics of lipid bilayers have been thoroughly investigated on larger 100 nm-1 μm silica spheres where the lipid bilayer exhibits the typical Lα bilayer phase, the molecular organization of lipids assembled on mesoscale (4-100 nm diameter) nanoparticles is scarce. Here, DSC, TEM and 2H and 31P solid-state NMR are implemented to probe the organization of 1,2-dipalmitoyl-d54-glycero-3-phosphocholine (DMPC-d54) assembled on mesoscale silica nanoparticles illustrating a significant deviation from Lα bilayer structure due to the increasing curvature of mesoscale supports. A biphasic system is observed that exhibits a combination of high-curvature, non-lamellar and lamellar phases for mesoscale (<100 nm) supports with evidence of an interdigitated phase on the smallest diameter support (4 nm).
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Affiliation(s)
- Dillan Stengel
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Dr, San Diego CA, 92182-1030, USA.
| | - Rich Thai
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Dr, San Diego CA, 92182-1030, USA.
| | - Yuan Li
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Dr, San Diego CA, 92182-1030, USA.
| | - Nikki M Peters
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Dr, San Diego CA, 92182-1030, USA.
| | - Gregory P Holland
- Department of Chemistry and Biochemistry, San Diego State University, 5500 Campanile Dr, San Diego CA, 92182-1030, USA.
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8
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Phan HT, Passos Gibson V, Guédin A, Ibarboure E, El Mammeri N, Grélard A, Le Meins JF, Dufourc EJ, Loquet A, Giasson S, Leblond Chain J. Switchable Lipids: From Conformational Switch to Macroscopic Changes in Lipid Vesicles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3072-3082. [PMID: 36793207 DOI: 10.1021/acs.langmuir.2c03149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
It has been shown that the use of conformationally pH-switchable lipids can drastically enhance the cytosolic drug delivery of lipid vesicles. Understanding the process by which the pH-switchable lipids disturb the lipid assembly of nanoparticles and trigger the cargo release is crucial to optimize the rational design of pH-switchable lipids. Here, we gather morphological observations (FF-SEM, Cryo-TEM, AFM, confocal microscopy), physicochemical characterization (DLS, ELS), as well as phase behavior studies (DSC, 2H NMR, Langmuir isotherm, and MAS NMR) to propose a mechanism of pH-triggered membrane destabilization. We demonstrate that the switchable lipids are homogeneously incorporated with other co-lipids (DSPC, cholesterol, and DSPE-PEG2000) and promote a liquid-ordered phase insensitive to temperature variation. Upon acidification, the protonation of the switchable lipids triggers a conformational switch altering the self-assembly properties of lipid nanoparticles. These modifications do not lead to a phase separation of the lipid membrane; however, they cause fluctuations and local defects, which result in morphological changes of the lipid vesicles. These changes are proposed to affect the permeability of vesicle membrane, triggering the release of the cargo encapsulated in the lipid vesicles (LVs). Our results confirm that pH-triggered release does not require major morphological changes, but can result from small defects affecting the lipid membrane permeability.
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Affiliation(s)
- Huu Trong Phan
- Faculty of Pharmacy, University of Montreal, Montréal H3C 3J7, Canada
| | | | - Aurore Guédin
- University of Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, Bordeaux F-33000 France
| | - Emmanuel Ibarboure
- Laboratoire de Chimie des Polymères Organiques LCPO Université de Bordeaux CNRS Bordeaux INP UMR 5629, Pessac F-33600, France
| | - Nadia El Mammeri
- Institut de Chimie et de Biologie des Membranes et des Nano-objets, Institut Européen de Chimie et Biologie, CNRS, UMR 5248, Université de Bordeaux, Pessac F-33600, France
| | - Axelle Grélard
- Institut de Chimie et de Biologie des Membranes et des Nano-objets, Institut Européen de Chimie et Biologie, CNRS, UMR 5248, Université de Bordeaux, Pessac F-33600, France
| | - Jean-François Le Meins
- Laboratoire de Chimie des Polymères Organiques LCPO Université de Bordeaux CNRS Bordeaux INP UMR 5629, Pessac F-33600, France
| | - Erick J Dufourc
- Institut de Chimie et de Biologie des Membranes et des Nano-objets, Institut Européen de Chimie et Biologie, CNRS, UMR 5248, Université de Bordeaux, Pessac F-33600, France
| | - Antoine Loquet
- Institut de Chimie et de Biologie des Membranes et des Nano-objets, Institut Européen de Chimie et Biologie, CNRS, UMR 5248, Université de Bordeaux, Pessac F-33600, France
| | - Suzanne Giasson
- Faculty of Pharmacy, University of Montreal, Montréal H3C 3J7, Canada
- Department of Chemistry, University of Montreal, Montréal H3C 3J7, Canada
| | - Jeanne Leblond Chain
- University of Bordeaux, CNRS, INSERM, ARNA, UMR 5320, U1212, Bordeaux F-33000 France
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9
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Navakauskas E, Niaura G, Strazdaite S. Effect of deuteration on a phosphatidylcholine lipid monolayer structure: New insights from vibrational sum-frequency generation spectroscopy. Colloids Surf B Biointerfaces 2022; 220:112866. [PMID: 36174490 DOI: 10.1016/j.colsurfb.2022.112866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 09/07/2022] [Accepted: 09/19/2022] [Indexed: 10/14/2022]
Abstract
We used vibrational sum-frequency generation (VSFG) spectroscopy to elucidate the possible effect of various levels of isotopic substitution (H/D) on the properties of the DPPC monolayer by probing DPPC/D2O interface. We found that deuteration of the choline group has a great impact on monolayer properties, while monolayers with deuterated alkyl chains do not exhibit any differences under our experimental conditions. In addition, deuteration of the choline group strongly affected the hydration of the phosphate group. We showed by probing symmetric stretching vibration of phosphate group that denser packing only slightly reduced the hydration of DPPC-d13 and DPPC-d75 monolayers. Moreover, addition of calcium ions, which generally cause a marked dehydration of the lipid monolayer, had no effect on lipid monolayers with deuterated choline group. We proposed that one way to explain this experimental finding could be deuteration induced changes in the structure of lipid's choline group, resulting in a well-hydrated but Ca2+ ion blocking structure. These results have important implications for various spectroscopic techniques, which commonly use deuteration of phospholipids to circumvent overlapping between vibrational bands.
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Affiliation(s)
- Edvinas Navakauskas
- Department of Organic Chemistry, Center for Physical Sciences and Technology (FTMC), Saulėtekis ave. 3, LT-10257 Vilnius, Lithuania
| | - Gediminas Niaura
- Department of Organic Chemistry, Center for Physical Sciences and Technology (FTMC), Saulėtekis ave. 3, LT-10257 Vilnius, Lithuania.
| | - Simona Strazdaite
- Department of Organic Chemistry, Center for Physical Sciences and Technology (FTMC), Saulėtekis ave. 3, LT-10257 Vilnius, Lithuania
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10
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Moir M, Yepuri N, Marshall D, Blanksby S, Darwish T. Synthesis of Perdeuterated Linoleic Acid‐d31 and Chain Deuterated 1‐Palmitoyl‐2‐linoleoyl‐sn‐glycero‐3‐phosphocholine‐d62. Adv Synth Catal 2022. [DOI: 10.1002/adsc.202200616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Michael Moir
- Australian Nuclear Science and Technology Organisation AUSTRALIA
| | - Nageshwar Yepuri
- Australian Nuclear Science and Technology Organisation AUSTRALIA
| | | | | | - Tamim Darwish
- Australian Nuclear Science and Technology Organisation AUSTRALIA
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11
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Malajczuk CJ, Stachura SS, Hendry JO, Mancera RL. Redefining the Molecular Interplay between Dimethyl Sulfoxide, Lipid Bilayers, and Dehydration. J Phys Chem B 2022; 126:2513-2529. [PMID: 35344357 DOI: 10.1021/acs.jpcb.2c00353] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The potentially damaging action of dimethyl sulfoxide (DMSO) on phospholipid bilayers remains a matter of controversy. We have conducted a series of long-scale molecular dynamics simulations of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayers at various levels of hydration in the presence of variable quantities of DMSO. These simulations provide evidence for a non-destructive dehydrating mechanism of action for DMSO on DOPC bilayers across a wide concentration range and levels of hydration. Specifically, under full- and low-hydration conditions, the bilayer underwent a minor lateral contraction, coinciding with surface dehydration in the presence of dilute DMSO solutions (XDMSO < 0.3). At higher DMSO concentrations, this bilayer structure was retained despite a progressive deterioration of the hydration structure at the interface. A similar convergence of bilayer structural properties was observed under dehydration conditions for 0.3 < XDMSO < 0.7. Destabilization occurred for dehydrated bilayers in the presence of XDMSO ≥ 0.7, suggesting the existence of a DMSO concentration and/or dehydration threshold. However, such DMSO concentrations far exceed those established as toxic to other cellular components. Our findings represent a computational model for DMSO-DOPC interactions that is consistent with a range of experimental characterizations, offering new molecular insights into the cryoprotective mechanisms of action of DMSO.
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Affiliation(s)
- Chris J Malajczuk
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
| | - Sławomir S Stachura
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
| | - James O Hendry
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
| | - Ricardo L Mancera
- Curtin Medical School, Curtin Health Innovation Research Institute and Curtin Institute for Computation, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
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12
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Hanashima S, Ikeda R, Matsubara Y, Yasuda T, Tsuchikawa H, Slotte JP, Murata M. Effect of cholesterol on the lactosylceramide domains in phospholipid bilayers. Biophys J 2022; 121:1143-1155. [PMID: 35218738 PMCID: PMC9034317 DOI: 10.1016/j.bpj.2022.02.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 10/22/2021] [Accepted: 02/22/2022] [Indexed: 11/02/2022] Open
Abstract
Lactosylceramide (LacCer) in the plasma membranes of immune cells is an important lipid for signaling in innate immunity through the formation of LacCer-rich domains together with cholesterol (Cho). However, the properties of the LacCer domains formed in multicomponent membranes remain unclear. In this study, we examined the properties of the LacCer domains formed in Cho containing 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) membranes by deuterium solid-state NMR and fluorescence lifetimes. The potent affinity of LacCer-LacCer (homophilic interaction) is known to induce a thermally stable gel phase in the unitary LacCer bilayer. In LacCer/Cho binary membranes, Cho gradually destabilized the LacCer gel phase to form the liquid-ordered (Lo) phase by its potent order effect. In the LacCer/POPC binary systems without Cho, the 2H NMR spectra of 10',10'-d2-LacCer and 18',18',18'-d3-LacCer probes revealed that LacCer was poorly miscible with POPC in the membranes and formed stable gel phases without being distributed in the liquid crystalline (Ld) domain. The lamellar structure of the LacCer/POPC membrane was gradually disrupted at around 60 °C, while the addition of Cho increased the thermal stability of the lamellarity. Furthermore, the area of the LacCer gel phase and its chain order were decreased in the LacCer/POPC/Cho ternary membranes, while the Lo domain, which was observed in the LacCer/Cho binary membrane, was not observed. Cho surrounding the LacCer gel domain liberated LacCer and facilitated forming the submicron- to nano-scale small domains in the Ld domain of the LacCer/POPC/Cho membranes, as revealed by the fluorescence lifetimes of trans-parinaric acid (tPA) and tPA-LacCer. Our findings on the membrane properties of the LacCer domains, particularly in the presence of Cho, would help elucidate the properties of the LacCer domains in biological membranes.
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Affiliation(s)
- Shinya Hanashima
- Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan.
| | - Ryuji Ikeda
- Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
| | - Yuki Matsubara
- Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
| | - Tomokazu Yasuda
- Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
| | - Hiroshi Tsuchikawa
- Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
| | - J Peter Slotte
- Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Tykistökatu 6 A, FIN 20520 Turku, Finland
| | - Michio Murata
- Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan; JST ERATO, Lipid Active Structure Project, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
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13
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Khairalla B, Brand I. Membrane Potentials Trigger Molecular-Scale Rearrangements in the Outer Membrane of Gram-Negative Bacteria. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:446-457. [PMID: 34963050 DOI: 10.1021/acs.langmuir.1c02820] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The structural complexity of the cell envelope of Gram-negative bacteria limits the fabrication of realistic models of bacterial cell membranes. A vertical Langmuir-Blodgett withdrawing was used to deposit a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) monolayer on the Au(111) surface. The second leaflet composed of di[3-deoxy-D-manno-octulosonyl]-lipid A (KLA) was deposited using Langmuir-Schaefer transfer. The use of an electrode material as a support for the POPE-KLA bilayer allowed electrochemical control of the membrane's stability, compactness, and structure. Capacitance-potential curves showed a typical pattern for the supported lipid bilayers electrochemical characteristic. The minimum membrane capacitance was ∼4 μF cm-2 and did not change in the following desorption-adsorption cycles, indicating the presence of a stable bilayer structure with an asymmetric composition of both leaflets. However, at a molecular scale, as elucidated in spectroelectrochemical experiments, large differences in the response of both leaflets to electric potentials were observed. The acyl chains in POPE and KLA existed in a liquid state. The quantitative analysis of the CH stretching modes indicated potential-driven reorientations in the hydrophobic fragment of the bilayer, already in the adsorbed state. To assign observed rearrangements to POPE and KLA lipids in both leaflets, per-deuterated d31-POPE was transferred into the inner leaflet. Since no potential-dependent changes of the CD2 stretching modes in the d31-POPE-KLA bilayer were observed, reorientations in the acyl chain region were assigned to the KLA molecules. Mg2+ ions were bound to the polar head groups of KLA. The strength of electrostatic interactions in the polar head group region of KLA was dependent on the direction of the electric field. At negative electric potentials, the binding of divalent cations weakened, which gave the KLA molecules increased orientational flexibility. This behavior in electric fields is peculiar for the outer membrane and indicates that the microbial cell membranes have different electrochemical properties than phospholipid bilayers.
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Affiliation(s)
- Bishoy Khairalla
- Department of Chemistry, University of Oldenburg, 26111 Oldenburg, Germany
| | - Izabella Brand
- Department of Chemistry, University of Oldenburg, 26111 Oldenburg, Germany
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14
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Duff AP, Cagnes M, Darwish TA, Krause-Heuer AM, Moir M, Recsei C, Rekas A, Russell RA, Wilde KL, Yepuri NR. Deuteration for biological SANS: Case studies, success and challenges in chemistry and biology. Methods Enzymol 2022; 677:85-126. [DOI: 10.1016/bs.mie.2022.08.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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15
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Perez-Salas U, Garg S, Gerelli Y, Porcar L. Deciphering lipid transfer between and within membranes with time-resolved small-angle neutron scattering. CURRENT TOPICS IN MEMBRANES 2021; 88:359-412. [PMID: 34862031 DOI: 10.1016/bs.ctm.2021.10.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This review focuses on time-resolved neutron scattering, particularly time-resolved small angle neutron scattering (TR-SANS), as a powerful in situ noninvasive technique to investigate intra- and intermembrane transport and distribution of lipids and sterols in lipid membranes. In contrast to using molecular analogues with potentially large chemical tags that can significantly alter transport properties, small angle neutron scattering relies on the relative amounts of the two most abundant isotope forms of hydrogen: protium and deuterium to detect complex membrane architectures and transport processes unambiguously. This review discusses advances in our understanding of the mechanisms that sustain lipid asymmetry in membranes-a key feature of the plasma membrane of cells-as well as the transport of lipids between membranes, which is an essential metabolic process.
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Affiliation(s)
- Ursula Perez-Salas
- Physics Department, University of Illinois at Chicago, Chicago, IL, United States.
| | - Sumit Garg
- Physics Department, University of Illinois at Chicago, Chicago, IL, United States
| | - Yuri Gerelli
- Department of Life and Environmental Sciences, Universita` Politecnica delle Marche, Ancona, Italy
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16
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Liu X, Counil C, Shi D, Mendoza-Ortega EE, Vela-Gonzalez AV, Maestro A, Campbell RA, Krafft MP. First quantitative assessment of the adsorption of a fluorocarbon gas on phospholipid monolayers at the air/water interface. J Colloid Interface Sci 2021; 593:1-10. [DOI: 10.1016/j.jcis.2021.02.073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 02/15/2021] [Accepted: 02/16/2021] [Indexed: 12/19/2022]
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17
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Kinnun JJ, Scott HL, Ashkar R, Katsaras J. Biomembrane Structure and Material Properties Studied With Neutron Scattering. Front Chem 2021; 9:642851. [PMID: 33987167 PMCID: PMC8110834 DOI: 10.3389/fchem.2021.642851] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 03/16/2021] [Indexed: 12/12/2022] Open
Abstract
Cell membranes and their associated structures are dynamical supramolecular structures where different physiological processes take place. Detailed knowledge of their static and dynamic structures is therefore needed, to better understand membrane biology. The structure–function relationship is a basic tenet in biology and has been pursued using a range of different experimental approaches. In this review, we will discuss one approach, namely the use of neutron scattering techniques as applied, primarily, to model membrane systems composed of lipid bilayers. An advantage of neutron scattering, compared to other scattering techniques, is the differential sensitivity of neutrons to isotopes of hydrogen and, as a result, the relative ease of altering sample contrast by substituting protium for deuterium. This property makes neutrons an ideal probe for the study of hydrogen-rich materials, such as biomembranes. In this review article, we describe isotopic labeling studies of model and viable membranes, and discuss novel applications of neutron contrast variation in order to gain unique insights into the structure, dynamics, and molecular interactions of biological membranes. We specifically focus on how small-angle neutron scattering data is modeled using different contrast data and molecular dynamics simulations. We also briefly discuss neutron reflectometry and present a few recent advances that have taken place in neutron spin echo spectroscopy studies and the unique membrane mechanical data that can be derived from them, primarily due to new models used to fit the data.
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Affiliation(s)
- Jacob J Kinnun
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Oak Ridge National Laboratory, Shull-Wollan Center, Oak Ridge, TN, United States
| | - Haden L Scott
- Large Scale Structures Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Oak Ridge National Laboratory, Shull-Wollan Center, Oak Ridge, TN, United States
| | - Rana Ashkar
- Department of Physics, Virginia Tech, Blacksburg, VA, United States.,Center for Soft Matter and Biological Physics, Virginia Tech, Blacksburg, VA, United States
| | - John Katsaras
- Oak Ridge National Laboratory, Shull-Wollan Center, Oak Ridge, TN, United States.,Sample Environment Group, Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, United States.,Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, United States
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18
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Conn CE, de Campo L, Whitten AE, Garvey CJ, Krause-Heuer AM, van 't Hag L. Membrane Protein Structures in Lipid Bilayers; Small-Angle Neutron Scattering With Contrast-Matched Bicontinuous Cubic Phases. Front Chem 2021; 8:619470. [PMID: 33644002 PMCID: PMC7903247 DOI: 10.3389/fchem.2020.619470] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 12/02/2020] [Indexed: 01/12/2023] Open
Abstract
This perspective describes advances in determining membrane protein structures in lipid bilayers using small-angle neutron scattering (SANS). Differentially labeled detergents with a homogeneous scattering length density facilitate contrast matching of detergent micelles; this has previously been used successfully to obtain the structures of membrane proteins. However, detergent micelles do not mimic the lipid bilayer environment of the cell membrane in vivo. Deuterated vesicles can be used to obtain the radius of gyration of membrane proteins, but protein-protein interference effects within the vesicles severely limits this method such that the protein structure cannot be modeled. We show herein that different membrane protein conformations can be distinguished within the lipid bilayer of the bicontinuous cubic phase using contrast-matching. Time-resolved studies performed using SANS illustrate the complex phase behavior in lyotropic liquid crystalline systems and emphasize the importance of this development. We believe that studying membrane protein structures and phase behavior in contrast-matched lipid bilayers will advance both biological and pharmaceutical applications of membrane-associated proteins, biosensors and food science.
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Affiliation(s)
- Charlotte E. Conn
- School of Science, STEM College, RMIT University, Melbourne, VIC, Australia
| | - Liliana de Campo
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
| | - Andrew E. Whitten
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
| | - Christopher J. Garvey
- Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
- Lund Institute for Advanced Neutron and X-Ray Science, Lund, Sweden
- Biolfim-Research Center for Biointerfaces and Biomedical Science Department, Faculty of Health and Society, Malmö University, Malmö, Sweden
| | - Anwen M. Krause-Heuer
- National Deuteration Facility, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia
| | - Leonie van 't Hag
- Department of Chemical Engineering, Monash University, Clayton, VIC, Australia
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19
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Pabois O, Ziolek RM, Lorenz CD, Prévost S, Mahmoudi N, Skoda MWA, Welbourn RJL, Valero M, Harvey RD, Grundy MML, Wilde PJ, Grillo I, Gerelli Y, Dreiss CA. Morphology of bile salts micelles and mixed micelles with lipolysis products, from scattering techniques and atomistic simulations. J Colloid Interface Sci 2020; 587:522-537. [PMID: 33189321 DOI: 10.1016/j.jcis.2020.10.101] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/23/2020] [Accepted: 10/25/2020] [Indexed: 12/17/2022]
Abstract
HYPOTHESES Bile salts (BS) are biosurfactants released into the small intestine, which play key and contrasting roles in lipid digestion: they adsorb at interfaces and promote the adsorption of digestive enzymes onto fat droplets, while they also remove lipolysis products from that interface, solubilising them into mixed micelles. Small architectural variations on their chemical structure, specifically their bile acid moiety, are hypothesised to underlie these conflicting functionalities, which should be reflected in different aggregation and solubilisation behaviour. EXPERIMENTS The micellisation of two BS, sodium taurocholate (NaTC) and sodium taurodeoxycholate (NaTDC), which differ by one hydroxyl group on the bile acid moiety, was assessed by pyrene fluorescence spectroscopy, and the morphology of aggregates formed in the absence and presence of fatty acids (FA) and monoacylglycerols (MAG) - typical lipolysis products - was resolved by small-angle X-ray/neutron scattering (SAXS, SANS) and molecular dynamics simulations. The solubilisation by BS of triacylglycerol-incorporating liposomes - mimicking ingested lipids - was studied by neutron reflectometry and SANS. FINDINGS Our results demonstrate that BS micelles exhibit an ellipsoidal shape. NaTDC displays a lower critical micellar concentration and forms larger and more spherical aggregates than NaTC. Similar observations were made for BS micelles mixed with FA and MAG. Structural studies with liposomes show that the addition of BS induces their solubilisation into mixed micelles, with NaTDC displaying a higher solubilising capacity.
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Affiliation(s)
- Olivia Pabois
- Institut Laue-Langevin, Grenoble 38000, France; Institute of Pharmaceutical Science, King's College London, London SE1 9NH, United Kingdom.
| | - Robert M Ziolek
- Department of Physics, King's College London, London WC2R 2LS, United Kingdom.
| | - Christian D Lorenz
- Department of Physics, King's College London, London WC2R 2LS, United Kingdom.
| | | | - Najet Mahmoudi
- ISIS Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom.
| | - Maximilian W A Skoda
- ISIS Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom.
| | - Rebecca J L Welbourn
- ISIS Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, United Kingdom.
| | - Margarita Valero
- Department of Physical Chemistry, University of Salamanca, Salamanca 37007, Spain.
| | - Richard D Harvey
- Department of Pharmaceutical Chemistry, University of Vienna, Vienna A-1090, Austria.
| | | | - Peter J Wilde
- Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, United Kingdom.
| | | | - Yuri Gerelli
- Institut Laue-Langevin, Grenoble 38000, France; Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona 60131, Italy.
| | - Cécile A Dreiss
- Institute of Pharmaceutical Science, King's College London, London SE1 9NH, United Kingdom.
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20
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Demidov VV. Site-specifically deuterated essential lipids as new drugs against neuronal, retinal and vascular degeneration. Drug Discov Today 2020; 25:1469-1476. [DOI: 10.1016/j.drudis.2020.03.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/07/2020] [Accepted: 03/23/2020] [Indexed: 01/10/2023]
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21
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Agarwal R, Smith MD, Smith JC. Capturing Deuteration Effects in a Molecular Mechanics Force Field: Deuterated THF and the THF-Water Miscibility Gap. J Chem Theory Comput 2020; 16:2529-2540. [PMID: 32175738 DOI: 10.1021/acs.jctc.9b01138] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Deuteration is a common chemical modification used in conjunction with experiments such as neutron scattering, NMR, and Fourier-transform infrared for the study of molecular systems. Under the Born-Oppenheimer (BO) approximation, while the underlying potential energy surface remains unchanged by isotopic substitutions, isotopic substitution still alters intramolecular vibrations, which in turn may alter intermolecular interactions. Molecular mechanics (MM) force fields used in classical molecular dynamics simulations are assumed to represent local approximations of the BO potential energy surfaces, and hence, MD simulations using simple isotopic mass substitutions should capture BO-compatible isotope effects. However, standard MM force-field parameterizations do not directly fit to the local harmonic quantum mechanical (QM) Hessian that describes the BO surface, but rather to QM normal-modes and/or mass-dependent internal-coordinate derived distortion energies. Here, using tetrahydrofuran (THF)-water mixtures as our model system, we show that not only does a simple mass-substitution approach fail to capture an experimentally characterized deuteration effect (the loss of the closed-loop miscibility gap associated with the complete deuteration of THF) but also it is necessary to generate new MM force-field parameters that correctly describe isotopic dependent vibrations to capture the experimental deuteration effect. We show that the origin of this failure is a result of using mass-dependent features to fit the THF MM force field, which unintentionally biases the bonded terms of the force field to represent only the isotopologue used during the original force-field parameterization. In addition, we make use of our isotopologue-corrected force field for D8THF to examine the molecular origins of the isotope-dependent loss of the THF-water miscibility gap.
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Affiliation(s)
- Rupesh Agarwal
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United States.,Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Micholas Dean Smith
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United States.,Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Jeremy C Smith
- UT/ORNL Center for Molecular Biophysics, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United States.,Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
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22
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The European Spallation Source in a personal view for the German Colloid and Soft Matter Society. Colloid Polym Sci 2020. [DOI: 10.1007/s00396-020-04628-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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23
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Luchini A, Delhom R, Cristiglio V, Knecht W, Wacklin-Knecht H, Fragneto G. Effect of ergosterol on the interlamellar spacing of deuterated yeast phospholipid multilayers. Chem Phys Lipids 2020; 227:104873. [PMID: 31926858 DOI: 10.1016/j.chemphyslip.2020.104873] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/14/2019] [Accepted: 01/03/2020] [Indexed: 12/17/2022]
Abstract
Sterols regulate several physico-chemical properties of biological membranes that are considered to be linked to function. Ergosterol is the main sterol molecule found in the cell membranes of yeasts and other fungi. Like the cholesterol found in mammalian cells, ergosterol has been proposed to have an ordering and condensing effect on saturated phospholipid membranes. The effects of cholesterol have been investigated extensively and result in an increase in the membrane thickness and the lipid acyl chain order. Less information is available on the effects of ergosterol on phospholipid membranes. Neutron Diffraction (ND) was used to characterize the effect of ergosterol on lipid multilayers prepared with deuterated natural phospholipids extracted from the yeast Pichia pastoris. The data show that the effect of ergosterol on membranes prepared from the natural phospholipid extract rich in unsaturated acyl chains, differs from what has been observed previously in membranes rich in saturated phospholipids. In contrast to cholesterol in synthetic phospholipid membranes, the presence of ergosterol up to 30 mol % in yeast phospholipid membranes only slightly altered the multilayer structure. In particular, only a small decrease in the multilayer d-spacing was observed as function of increasing ergosterol concentrations. This result highlights the need for further investigation to elucidate the effects of ergosterol in biological lipid mixtures.
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Affiliation(s)
- Alessandra Luchini
- Niels Bohr Institute, University of Copenhagen, UniversiteTsparken 5, 2100 Copenhagen, Denmark.
| | - Robin Delhom
- Department of Biology, Lund University, Sölvegatan 35, 22362 Lund, Sweden
| | | | - Wolfgang Knecht
- Department of Biology, Lund University, Sölvegatan 35, 22362 Lund, Sweden; Lund Protein Production Platform, Lund University, Sölvegatan 35, 22362 Lund, Sweden
| | - Hanna Wacklin-Knecht
- European Spallation Source ERIC, P.O. Box 176, 22100 Lund, Sweden; Division of Physical Chemistry, Lund University, P.O.Box 124, 22100 Lund, Sweden
| | - Giovanna Fragneto
- Institut Laue-Langevin, 71 Avenue Des Martyrs, 38000, Grenoble, France.
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24
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Usuda H, Hishida M, Kelley EG, Yamamura Y, Nagao M, Saito K. Interleaflet coupling of n-alkane incorporated bilayers. Phys Chem Chem Phys 2020; 22:5418-5426. [PMID: 31904060 DOI: 10.1039/c9cp06059f] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The relationship between the membrane bending modulus (κ) and compressibility modulus (KA) depends on the extent of coupling between the two monolayers (leaflets). Using neutron spin echo (NSE) spectroscopy, we investigate the effects of n-alkanes on the interleaflet coupling of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers. Structural studies with small-angle X-ray and neutron scattering (SAXS and SANS) showed that the bilayer thickness increased with increasing n-alkane length, while NSE suggested that the bilayers became softer. Additional measurements of the membrane thickness fluctuations with NSE suggested that the changes in elastic moduli were due to a decrease in coupling between the leaflets upon addition of the longer n-alkanes. The decreased coupling with elongating n-alkane length was explained based on the n-alkane distribution within the bilayers characterized by SANS measurement of bilayers composed of protiated DPPC and deuterated n-alkanes. A higher fraction of the incorporated long n-alkanes were concentrated at the central plane of the bilayers and decreased the physical interaction between the leaflets. Using NSE and SANS, we successfully correlated changes in the mesoscopic collective dynamics and microscopic membrane structure upon incorporation of n-alkanes.
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Affiliation(s)
- Hatsuho Usuda
- Department of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
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25
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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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