1
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Kumar A, Daschakraborty S. Anomalous lateral diffusion of lipids during the fluid/gel phase transition of a lipid membrane. Phys Chem Chem Phys 2023; 25:31431-31443. [PMID: 37962400 DOI: 10.1039/d3cp04081j] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
A lipid membrane undergoes a phase transition from fluid to gel phase upon changing external thermodynamic conditions, such as decreasing temperature and increasing pressure. Extremophilic organisms face the challenge of preventing this deleterious phase transition. The main focus of their adaptive strategy is to facilitate effective temperature sensing through sensor proteins, relying on the drastic changes in packing density and membrane fluidity during the phase transition. Although the changes in packing density parameters due to the fluid/gel phase transition are studied in detail, the impact on membrane fluidity is less explored in the literature. Understanding the lateral diffusive dynamics of lipids in response to temperature, particularly during the fluid/gel phase transition, is albeit crucial. Here we have simulated the phase transition of a single component lipid membrane composed of dipalmitoylphosphatidylcholine (DPPC) lipids using a coarse-grained (CG) model and studied the changes of the structural and dynamical properties. It is observed that near the phase transition point, both fluid and gel phase domains coexist together. The dynamics remains highly non-Gaussian for a long time even when the mean square displacement reaches the Fickian regime at a much earlier time. This Fickian yet non-Gaussian diffusion (FnGD) is a characteristic of a highly heterogeneous system, previously observed for the lateral diffusion of lipids in raft mimetic membranes having liquid-ordered and liquid-disordered phases co-existing together. We have analyzed the molecular trajectories and calculated the jump-diffusion of the lipids, stemming from sudden jump translations, using a translational jump-diffusion (TJD) approach. An overwhelming contribution of the jump-diffusion of the lipids is observed suggesting anomalous diffusion of lipids during fluid/gel phase transition of the membrane. These results are important in unravelling the intricate nature of lipid diffusion during the phase transition of the membrane and open up a new possibility of investigating the most significant change of membrane properties during phase transition, which can be effectively sensed by proteins.
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Affiliation(s)
- Abhay Kumar
- Department of Chemistry, Indian Institute of Technology Patna, Bihar 801106, India.
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2
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Klacsová M, Čelková A, Búcsi A, Martínez JC, Uhríková D. Interaction of GC376, a SARS-COV-2 M PRO inhibitor, with model lipid membranes. Colloids Surf B Biointerfaces 2022; 220. [PMCID: PMC9557139 DOI: 10.1016/j.colsurfb.2022.112918] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Partitioning and effect of antiviral GC376, a potential SARS-CoV-2 inhibitor, on model lipid membranes was studied using dynamic light scattering (DLS), UV–VIS spectrometry, Excimer fluorescence, Differential scanning calorimetry (DSC) and Small- and Wide-angle X-ray scattering (SAXS/WAXS). Partition coefficient of GC376 between lipid and water phase was found to be low, reaching KP = 46.8 ± 18.2. Results suggest that GC376 partitions into lipid bilayers at the level of lipid head-groups, close to the polar/hydrophobic interface. Changes in structural and thermodynamic properties strongly depend on the GC376/lipid mole ratio. Already at lowest mole ratios GC376 induces increase of lateral pressures, mainly in the interfacial region of the bilayer. Hereby, the pre- and main-transition temperature of the lipid system increases, what is attributed to tighter packing of acyl chains induced by GC376. At GC376/DPPC ≥ 0.03 mol/mol we detected formation of domains with different GC376 content resulting in the lateral phase separation and changes in both, main transition temperature and enthalpy. The observed changes are attributed to the response of the system on the increased lateral stresses induced by partitioning of GC376. Obtained results are discussed in context of liposome-based drug delivery systems for GC376 and in context of indirect mechanism of virus replication inhibition.
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Affiliation(s)
- Mária Klacsová
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, Odbojárov10, 832 32 Bratislava, Slovakia,Corresponding author
| | - Adriána Čelková
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, Odbojárov10, 832 32 Bratislava, Slovakia
| | - Alexander Búcsi
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, Odbojárov10, 832 32 Bratislava, Slovakia
| | | | - Daniela Uhríková
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University Bratislava, Odbojárov10, 832 32 Bratislava, Slovakia
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3
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Heller WT. Small-Angle Neutron Scattering for Studying Lipid Bilayer Membranes. Biomolecules 2022; 12:1591. [PMID: 36358941 PMCID: PMC9687511 DOI: 10.3390/biom12111591] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/18/2022] [Accepted: 10/26/2022] [Indexed: 09/23/2023] Open
Abstract
Small-angle neutron scattering (SANS) is a powerful tool for studying biological membranes and model lipid bilayer membranes. The length scales probed by SANS, being from 1 nm to over 100 nm, are well-matched to the relevant length scales of the bilayer, particularly when it is in the form of a vesicle. However, it is the ability of SANS to differentiate between isotopes of hydrogen as well as the availability of deuterium labeled lipids that truly enable SANS to reveal details of membranes that are not accessible with the use of other techniques, such as small-angle X-ray scattering. In this work, an overview of the use of SANS for studying unilamellar lipid bilayer vesicles is presented. The technique is briefly presented, and the power of selective deuteration and contrast variation methods is discussed. Approaches to modeling SANS data from unilamellar lipid bilayer vesicles are presented. Finally, recent examples are discussed. While the emphasis is on studies of unilamellar vesicles, examples of the use of SANS to study intact cells are also presented.
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Affiliation(s)
- William T Heller
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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4
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DiPasquale M, Nguyen MHL, Pabst G, Marquardt D. Partial Volumes of Phosphatidylcholines and Vitamin E: α-Tocopherol Prefers Disordered Membranes. J Phys Chem B 2022; 126:6691-6699. [PMID: 36027485 DOI: 10.1021/acs.jpcb.2c04209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Despite its discovery over 95 years ago, the biological and nutritional roles of vitamin E remain subjects of much controversy. Though it is known to possess antioxidant properties, recent assertions have implied that vitamin E may not be limited to this function in living systems. Through densitometry measurements and small-angle X-ray scattering we observe favorable interactions between α-tocopherol and unsaturated phospholipids, with more favorable interactions correlating to an increase in lipid chain unsaturation. Our data provide evidence that vitamin E may preferentially associate with oxygen sensitive lipids─an association that is considered innate for a viable membrane antioxidant.
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Affiliation(s)
- Mitchell DiPasquale
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | - Michael H L Nguyen
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, Graz 8010, Austria.,BioTechMed-Graz, Graz 8010, Austria
| | - Drew Marquardt
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada.,Department of Physics, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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5
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Interplay between bulk aggregates, surface properties and foam stability of nonionic surfactants. Adv Colloid Interface Sci 2022; 302:102618. [PMID: 35245855 DOI: 10.1016/j.cis.2022.102618] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2021] [Revised: 02/15/2022] [Accepted: 02/20/2022] [Indexed: 11/21/2022]
Abstract
In our previous study (Mustan et al. 2021) we showed that foams formed from two oil-soluble nonionic surfactants (Span 60 and Brij 72) can remain stable for more than 10 days at room temperature at high sugar concentration. The major aim of the current study is to reveal the interrelation between the surfactant structure and foam stability by investigating 6 polyoxyethelene alkyl ethers and 12 fatty acid esters with a wide variety of hydrophobic chain lengths (C12; C16; C18 and C18:1) and hydrophilic head-groups (sorbitol, glycerol, sucrose). Foams stable for more than 100 days at room temperature are obtained when sucrose palmitate or stearate (P1670 or S1670) are used as surfactants. This exceptional foam stability is related to the gelation of the aqueous phase and to the formation of solid adsorption layer with zero surface tension upon compression, thus preventing water drainage and decelerating the bubble Ostwald ripening. The foam stability decreases with (i) increasing the number of EO groups in polyoxyethylene alkyl ethers and in fatty acid sorbitan esters; (ii) decreasing the number of C-atoms in the surfactant tail for all studied surfactants; (iii) addition of double bond in the surfactant tail. The lower foam stability in all three cases is related to the worse packing of the surfactant molecules within the adsorption layer, leading to faster Ostwald ripening and subsequent bubble coalescence. The diesters present as admixture in the fatty acid esters play an important role in the foam stabilization by further compacting the adsorption layers and lowering the rate of Ostwald ripening. These conclusions can be used as a predictive tool for surfactant selection in the development of food or pharmaceutical foam concentrates that can be diluted before final use.
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6
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Maiti A, Daschakraborty S. Can Urea and Trimethylamine- N-oxide Prevent the Pressure-Induced Phase Transition of Lipid Membrane? J Phys Chem B 2022; 126:1426-1440. [PMID: 35139638 DOI: 10.1021/acs.jpcb.1c08891] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Organisms dwelling in ocean trenches are exposed to the high hydrostatic pressure of ocean water. Increasing pressure can alter the membrane packing density and fluidity and trigger the fluid-to-gel phase transition. To combat environmental stress, the organisms synthesize small polar solutes, which are known as osmolytes. Urea and trimethylamine-N-oxide (TMAO) are two such solutes found in deep-sea creatures. While TMAO stabilizes protein, urea induces protein denaturation. These solutes strongly influence the packing density and membrane fluidity of the lipid bilayer at different conditions. But can these solutes affect the pressure-induced phase transition of the lipid membrane? In the present work, we have studied the effect of these two solutes on pressure-induced fluid-to-gel phase transition based on the all-atom molecular dynamics (MD) simulation approach. A high-pressure-stimulated fluid-to-gel phase transition of the membrane is seen at 800 bar, which is consistent with previous experiments. We have also observed that in the low-pressure region (1-400 bar), urea slightly increases the membrane fluidity where TMAO decreases the same. However, the phase transition pressure remains almost unchanged on the addition of urea while TMAO shifts the phase transition toward a lower pressure. We have found that the hydrogen (H)-bond interaction between lipid and urea plays an important role in preserving the fluidity of the membrane in the low-pressure zone. However, at a higher pressure, both water and urea are excluded from the membrane surface. TMAO is also excluded from the interfacial region of the membrane at all pressures. Exclusion from the membrane surface further triggers the phase transition of the lipid membrane from the fluid to gel phase at a high pressure.
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Affiliation(s)
- Archita Maiti
- Department of Chemistry, Indian Institute of Technology Patna, Bihar 801106, India
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7
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Maiti A, Daschakraborty S. How Do Urea and Trimethylamine N-Oxide Influence the Dehydration-Induced Phase Transition of a Lipid Membrane? J Phys Chem B 2021; 125:10149-10165. [PMID: 34486370 DOI: 10.1021/acs.jpcb.1c05852] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Living organisms are often exposed to extreme dehydration, which is detrimental to the structure and function of the cell membrane. The lipid membrane undergoes fluid-to-gel phase transition due to dehydration and thus loses fluidity and functionality. To protect the fluid phase of the bilayer these organisms adopt several strategies. Enhanced production of small polar organic solutes (also called osmolytes) is one such strategy. Urea and trimethylamine N-oxide (TMAO) are two osmolytes found in different organisms combating osmotic stress. Previous experiments have found that both these osmolytes have strong effects on lipid membrane under different hydration conditions. Urea prevents the dehydration-induced phase transition of the lipid membrane by directly interacting with the lipids, while TMAO does not inhibit the phase transition. To provide atomistic insights, we have carried out all-atom molecular dynamics (MD) simulation of a lipid membrane under varying hydration levels and studied the effect of these osmolytes on different structural and dynamic properties of the membrane. This study suggests that urea significantly inhibits the dehydration-induced fluid-to-gel phase transition by strongly interacting with the lipid membrane via hydrogen bonds, which balances the reduced lipid hydration due to the decreasing water content. In contrast, TMAO is excluded from the membrane surface due to unfavorable interaction with the lipids. This induces further dehydration of the lipids which reinforces the fluid-to-gel phase transition. We have also studied the counteractive role of TMAO on the effect of urea on lipid membrane when both the osmolytes are present. TMAO draws some urea molecules out of the membrane and thereby reduces the effect of urea on the lipid membrane at lower hydration levels. This is similar to the counteraction of urea's deleterious effects on protein by TMAO. All these observations are consistent with the experimental results and thus provide deep molecular insights into the role of these osmolytes in protecting the fluid phase of the membrane, the key survival strategy against osmotic-stress-induced dehydration.
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Affiliation(s)
- Archita Maiti
- Department of Chemistry, Indian Institute of Technology Patna, Bihar 801106, India
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8
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Seper BC, Ko A, Abma AF, Folkerts AD, Tristram-Nagle S, Harper PE. Methylene volumes in monoglyceride bilayers are larger than in liquid alkanes. Chem Phys Lipids 2019; 226:104833. [PMID: 31738879 DOI: 10.1016/j.chemphyslip.2019.104833] [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: 07/29/2019] [Revised: 09/26/2019] [Accepted: 10/09/2019] [Indexed: 11/26/2022]
Abstract
The densities as a function of temperature of four fully hydrated saturated monoglycerides with even chain lengths ranging from eight to fourteen were determined by vibrating tube densitometry and their phase transition temperatures were determined by differential scanning calorimetry (DSC). We find the volume of a methylene group in a monoglyceride bilayer is 2% larger than in liquid alkanes at physiological temperatures, similar to the methylene group volumes found in phosphatidylcholine (PC) bilayers. Additionally, we carefully consider the traditional method of calculating component volumes from experimental data and note potential difficulties in this approach. In the literature, the ratio of terminal methyl volume (CH3) to methylene (CH2) volumes is typically assumed to be 2. By analysis of literature alkane data, we find this ratio actually ranges from 1.9 to 2.3 for temperatures ranging from 0 °C to 100 °C. For a rough sense of scale, we note that to effect a 2% reduction in volume requires of order 200 atmospheres of pressure, and pressures of this magnitude are biologically relevant. For instance, this amount of pressure is sufficient to reverse the effect of anesthesia. The component volumes obtained are an important parameter used for determining the structure of lipid bilayers and for molecular dynamics simulations.
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Affiliation(s)
- Brian C Seper
- Department of Physics and Astronomy, Calvin University, Grand Rapids, MI 49546, USA
| | - Anthony Ko
- Biological Physics Group, Physics Department, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
| | - Aaron F Abma
- Department of Physics and Astronomy, Calvin University, Grand Rapids, MI 49546, USA
| | - Andrew D Folkerts
- Department of Physics and Astronomy, Calvin University, Grand Rapids, MI 49546, USA
| | - Stephanie Tristram-Nagle
- Biological Physics Group, Physics Department, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
| | - Paul E Harper
- Department of Physics and Astronomy, Calvin University, Grand Rapids, MI 49546, USA.
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9
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Erimban S, Daschakraborty S. Compatibility of advanced water models with a united atom model of lipid in lipid bilayer simulation. J Chem Phys 2019. [DOI: 10.1063/1.5108830] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Shakkira Erimban
- Department of Chemistry, Indian Institute of Technology Patna, Bihar 801106, India
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10
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Nagle JF, Venable RM, Maroclo-Kemmerling E, Tristram-Nagle S, Harper PE, Pastor RW. Revisiting Volumes of Lipid Components in Bilayers. J Phys Chem B 2019; 123:2697-2709. [PMID: 30836006 DOI: 10.1021/acs.jpcb.8b12010] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In addition to obtaining the highly precise volumes of lipids in lipid bilayers, it has been desirable to obtain the volumes of parts of each lipid, such as the methylenes and terminal methyls on the hydrocarbon chains and the head group. Obtaining such component volumes from experiment and from simulations is re-examined, first by distinguishing methods based on apparent versus partial molar volumes. Although somewhat different, both these methods give results that are counterintuitive and that differ from results obtained by a more local method that can only be applied to simulations. These comparisons reveal differences in the average methylene component volume that result in larger differences in the head group component volumes. Literature experimental volume data for unsaturated phosphocholines and for alkanes have been used and new data have been acquired for saturated phosphocholines. Data and simulations cover extended ranges of temperature to assess both the temperature and chain length dependence of the component volumes. A new method to refine the determination of component volumes is proposed that uses experimental data for different chain lengths at temperatures guided by the temperature dependence determined in simulations. These refinements enable more precise comparisons of the component volumes of different lipids and alkanes in different phases. Finally, the notion of free volume is extended to components using the Lennard-Jones radii to estimate the excluded volume of each component. This analysis reveals that head group free volumes are relatively independent of thermodynamic phase, whereas both the methylene and methyl free volumes increase dramatically when bilayers transition from gel to fluid.
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Affiliation(s)
- John F Nagle
- Department of Physics , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Richard M Venable
- Laboratory of Computational Biology , National Heart, Lung, and Blood Institute, National Institutes of Health , Bethesda , Maryland 20892 , United States
| | | | - Stephanie Tristram-Nagle
- Department of Physics , Carnegie Mellon University , Pittsburgh , Pennsylvania 15213 , United States
| | - Paul E Harper
- Department of Physics & Astronomy , Calvin College , Grand Rapids , Michigan 49546 , United States
| | - Richard W Pastor
- Laboratory of Computational Biology , National Heart, Lung, and Blood Institute, National Institutes of Health , Bethesda , Maryland 20892 , United States
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11
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Cockcroft JK, Shamsabadi A, Wu H, Rennie AR. Understanding the structure and dynamics of cationic surfactants from studies of pure solid phases. Phys Chem Chem Phys 2019; 21:25945-25951. [DOI: 10.1039/c9cp04486h] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Unravelling the phase behaviour of n-alkyltrimethylammonium bromides (C10 to C18): from tight-packed interdigitation to rotational disorder with increasing temperature.
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Affiliation(s)
| | - André Shamsabadi
- Department of Chemistry
- Christopher Ingold Laboratories
- UCL
- London WC1H 0AJ
- UK
| | - Han Wu
- Department of Chemical Engineering
- UCL
- London WC1E 7JE
- UK
| | - Adrian R. Rennie
- Centre for Neutron Scattering
- Uppsala University
- 75120 Uppsala
- Sweden
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12
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Heberle FA, Pabst G. Complex biomembrane mimetics on the sub-nanometer scale. Biophys Rev 2017; 9:353-373. [PMID: 28717925 PMCID: PMC5578918 DOI: 10.1007/s12551-017-0275-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 06/26/2017] [Indexed: 12/12/2022] Open
Abstract
Biomimetic lipid vesicles are indispensable tools for gaining insight into the biophysics of cell physiology on the molecular level. The level of complexity of these model systems has steadily increased, and now spans from domain-forming lipid mixtures to asymmetric lipid bilayers. Here, we review recent progress in the development and application of elastic neutron and X-ray scattering techniques for studying these systems in situ and under physiologically relevant conditions on the nanometer to sub-nanometer length scales. In particular, we focus on: (1) structural details of coexisting liquid-ordered and liquid-disordered domains, including their thickness and lipid packing mismatch as a function of a size transition from nanoscopic to macroscopic domains; (2) membrane-mediated protein partitioning into lipid domains; (3) the role of the aqueous medium in tuning interactions between membranes and domains; and (4) leaflet-specific structure in asymmetric bilayers and passive lipid flip-flop.
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Affiliation(s)
- Frederick A Heberle
- The Bredesen Center, University of Tennessee, Knoxville, TN, 37996, USA.,Joint Institute for Biological Sciences and Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, University of Graz, 8010, Graz, Austria. .,BioTechMed-Graz, 8010, Graz, Austria.
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13
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Frampton MB, Marquardt D, Letofsky-Papst I, Pabst G, Zelisko PM. Analysis of Trisiloxane Phosphocholine Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4948-4953. [PMID: 28471667 PMCID: PMC5462096 DOI: 10.1021/acs.langmuir.6b04162] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We have synthesized unique siloxane phosphocholines and characterized their aggregates in aqueous solution. The siloxane phosphocholines form nearly monodisperse vesicles in aqueous solution without the need for secondary extrusion processes. The area/lipid, lipid volume, and bilayer thickness were determined from small-angle X-ray scattering experiments. The impetus for the spontaneous formation of unilamellar vesicles by these compounds is discussed.
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Affiliation(s)
- Mark B. Frampton
- Department of Chemistry and Centre for Biotechnology, Brock University, St. Catharines, Ontario, Canada
| | - Drew Marquardt
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, NAWI Graz, Graz, 8010, Austria
- BioTechMed-Graz, Graz, 8010, Austria
| | - Ilse Letofsky-Papst
- Graz University of Technology, NAWI Graz, Institute for Electron Microscopy & Nanoanalysis and Center for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria
| | - Georg Pabst
- Institute of Molecular Biosciences, Biophysics Division, University of Graz, NAWI Graz, Graz, 8010, Austria
- BioTechMed-Graz, Graz, 8010, Austria
| | - Paul M. Zelisko
- Department of Chemistry and Centre for Biotechnology, Brock University, St. Catharines, Ontario, Canada
- Corresponding Author: Paul M. Zelisko
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14
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Belička M, Weitzer A, Pabst G. High-resolution structure of coexisting nanoscopic and microscopic lipid domains. SOFT MATTER 2017; 13:1823-1833. [PMID: 28170020 DOI: 10.1039/c6sm02727j] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
We studied coexisting micro- and nanoscopic liquid-ordered/liquid-disordered domains in fully hydrated multilamellar vesicles using small-angle X-ray scattering. Large domains exhibited long-range out-of-plane positional correlations of like domains, consistent with previous reports. In contrast, such correlations were absent in nanoscopic domains. Advancing a global analysis of the in situ data allowed us to gain a deep insight into the structural and elastic properties of the coexisting domains, including the partitioning of cholesterol in each domain. In agreement with a previous report, we found that the thickness mismatch between ordered and disordered domains decreased for nanoscopic domains. At the same time, we found also the lipid packing mismatch to be decreased for nano-domains, mainly due to the liquid-disordered domains becoming more densely packed when decreasing their size.
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Affiliation(s)
- Michal Belička
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, A-8010 Graz, Austria. and BioTechMed-Graz, A-8010 Graz, Austria
| | - Anna Weitzer
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, A-8010 Graz, Austria. and BioTechMed-Graz, A-8010 Graz, Austria
| | - Georg Pabst
- University of Graz, Institute of Molecular Biosciences, Biophysics Division, NAWI Graz, Humboldtstr. 50/III, A-8010 Graz, Austria. and BioTechMed-Graz, A-8010 Graz, Austria
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15
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Litz JP, Thakkar N, Portet T, Keller SL. Depletion with Cyclodextrin Reveals Two Populations of Cholesterol in Model Lipid Membranes. Biophys J 2017; 110:635-645. [PMID: 26840728 DOI: 10.1016/j.bpj.2015.11.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 11/06/2015] [Accepted: 11/10/2015] [Indexed: 10/22/2022] Open
Abstract
Recent results provide evidence that cholesterol is highly accessible for removal from both cell and model membranes above a threshold concentration that varies with membrane composition. Here we measured the rate at which methyl-β-cyclodextrin depletes cholesterol from a supported lipid bilayer as a function of cholesterol mole fraction. We formed supported bilayers from two-component mixtures of cholesterol and a PC (phosphatidylcholine) lipid, and we directly visualized the rate of decrease in area of the bilayers with fluorescence microscopy. Our technique yields the accessibility of cholesterol over a wide range of concentrations (30-66 mol %) for many individual bilayers, enabling fast acquisition of replicate data. We found that the bilayers contain two populations of cholesterol, one with low surface accessibility and the other with high accessibility. A larger fraction of the total membrane cholesterol appears in the more accessible population when the acyl chains of the PC-lipid tails are more unsaturated. Our findings are most consistent with the predictions of the condensed-complex and cholesterol bilayer domain models of cholesterol-phospholipid interactions in lipid membranes.
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Affiliation(s)
- Jonathan P Litz
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Niket Thakkar
- Department of Chemistry, University of Washington, Seattle, Washington; Department of Applied Mathematics, University of Washington, Seattle, Washington
| | - Thomas Portet
- Department of Chemistry, University of Washington, Seattle, Washington
| | - Sarah L Keller
- Department of Chemistry, University of Washington, Seattle, Washington; Department of Physics, University of Washington, Seattle, Washington.
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16
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Poger D, Caron B, Mark AE. Validating lipid force fields against experimental data: Progress, challenges and perspectives. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1556-65. [DOI: 10.1016/j.bbamem.2016.01.029] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/07/2016] [Accepted: 01/27/2016] [Indexed: 01/16/2023]
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17
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Structural Significance of Lipid Diversity as Studied by Small Angle Neutron and X-ray Scattering. MEMBRANES 2015; 5:454-72. [PMID: 26402708 PMCID: PMC4584290 DOI: 10.3390/membranes5030454] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/15/2015] [Indexed: 11/17/2022]
Abstract
We review recent developments in the rapidly growing field of membrane biophysics, with a focus on the structural properties of single lipid bilayers determined by different scattering techniques, namely neutron and X-ray scattering. The need for accurate lipid structural properties is emphasized by the sometimes conflicting results found in the literature, even in the case of the most studied lipid bilayers. Increasingly, accurate and detailed structural models require more experimental data, such as those from contrast varied neutron scattering and X-ray scattering experiments that are jointly refined with molecular dynamics simulations. This experimental and computational approach produces robust bilayer structural parameters that enable insights, for example, into the interplay between collective membrane properties and its components (e.g., hydrocarbon chain length and unsaturation, and lipid headgroup composition). From model studies such as these, one is better able to appreciate how a real biological membrane can be tuned by balancing the contributions from the lipid's different moieties (e.g., acyl chains, headgroups, backbones, etc.).
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Gallová J, Klacsová M, Devínsky F, Balgavý P. Partial volumes of cholesterol and monounsaturated diacylphosphatidylcholines in mixed bilayers. Chem Phys Lipids 2015; 190:1-8. [DOI: 10.1016/j.chemphyslip.2015.06.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 05/20/2015] [Accepted: 06/15/2015] [Indexed: 10/23/2022]
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Belička M, Gerelli Y, Kučerka N, Fragneto G. The component group structure of DPPC bilayers obtained by specular neutron reflectometry. SOFT MATTER 2015; 11:6275-6283. [PMID: 26160133 DOI: 10.1039/c5sm00274e] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Specular neutron reflectometry was measured on a floating bilayer system consisting of 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine deposited over a 1,2-dibehenoyl-sn-glycero-3-phosphocholine bilayer at 25 and 55 °C. The internal structure of lipid bilayers was described by a one-dimensional neutron scattering length density profile model, originally developed for the evaluation of small-angle scattering data. The reflectivity data from the supported bilayer were evaluated separately and used further as constraints in modeling the floating bilayer reflectivity curves. The model reflectivity curves successfully describe the experimental reflectivities of the supported bilayer in the gel phase and the floating bilayer system in the liquid-crystalline phase. The results yield an internal structure of a deposited bilayer and a floating bilayer on the level of component groups of lipid molecules. The obtained structure of the floating d62-diC16:0PC bilayer displays high resemblance of the bilayer structure in the form of unilamellar vesicles. At the same time, however, the results show differences in comparison to unilamellar vesicle bilayers, most likely due to the undulations of supported bilayers.
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Affiliation(s)
- Michal Belička
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, SK-832 32 Bratislava, Slovakia.
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A systematic molecular dynamics simulation study of temperature dependent bilayer structural properties. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:2520-9. [PMID: 24953542 DOI: 10.1016/j.bbamem.2014.06.010] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 06/07/2014] [Accepted: 06/11/2014] [Indexed: 11/21/2022]
Abstract
Although lipid force fields (FFs) used in molecular dynamics (MD) simulations have proved to be accurate, there has not been a systematic study on their accuracy over a range of temperatures. Motivated by the X-ray and neutron scattering measurements of common phosphatidylcholine (PC) bilayers (Kučerka et al. BBA. 1808: 2761, 2011), the CHARMM36 (C36) FF accuracy is tested in this work with MD simulations of six common PC lipid bilayers over a wide range of temperatures. The calculated scattering form factors and deuterium order parameters from the C36 MD simulations agree well with the X-ray, neutron, and NMR experimental data. There is excellent agreement between MD simulations and experimental estimates for the surface area per lipid, bilayer thickness (DB), hydrophobic thickness (DC), and lipid volume (VL). The only minor discrepancy between simulation and experiment is a measure of (DB-DHH)/2 where DHH is the distance between the maxima in the electron density profile along the bilayer normal. Additional MD simulations with pure water and heptane over a range of temperatures provide explanations of possible reasons causing the minor deviation. Overall, the C36 FF is accurate for use with liquid crystalline PC bilayers of varying chain types and over biologically relevant temperatures.
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Belička M, Klacsová M, Karlovská J, Westh P, Devínsky F, Balgavý P. Molecular and component volumes of N,N-dimethyl-N-alkylamine N-oxides in DOPC bilayers. Chem Phys Lipids 2014; 180:1-6. [DOI: 10.1016/j.chemphyslip.2014.02.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2013] [Revised: 02/19/2014] [Accepted: 02/21/2014] [Indexed: 11/28/2022]
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22
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Belička M, Kučerka N, Uhríková D, Islamov AK, Kuklin AI, Devínsky F, Balgavý P. Effects of N,N-dimethyl-N-alkylamine-N-oxides on DOPC bilayers in unilamellar vesicles: small-angle neutron scattering study. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2014; 43:179-89. [DOI: 10.1007/s00249-014-0954-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2014] [Revised: 02/27/2014] [Accepted: 03/10/2014] [Indexed: 10/25/2022]
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23
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Heftberger P, Kollmitzer B, Heberle FA, Pan J, Rappolt M, Amenitsch H, Kučerka N, Katsaras J, Pabst G. Global small-angle X-ray scattering data analysis for multilamellar vesicles: the evolution of the scattering density profile model. J Appl Crystallogr 2014; 47:173-180. [PMID: 24587787 PMCID: PMC3937811 DOI: 10.1107/s1600576713029798] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/30/2013] [Indexed: 12/04/2022] Open
Abstract
The highly successful scattering density profile (SDP) model, used to jointly analyze small-angle X-ray and neutron scattering data from unilamellar vesicles, has been adapted for use with data from fully hydrated, liquid crystalline multilamellar vesicles (MLVs). Using a genetic algorithm, this new method is capable of providing high-resolution structural information, as well as determining bilayer elastic bending fluctuations from standalone X-ray data. Structural parameters such as bilayer thickness and area per lipid were determined for a series of saturated and unsaturated lipids, as well as binary mixtures with cholesterol. The results are in good agreement with previously reported SDP data, which used both neutron and X-ray data. The inclusion of deuterated and non-deuterated MLV neutron data in the analysis improved the lipid backbone information but did not improve, within experimental error, the structural data regarding bilayer thickness and area per lipid.
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Affiliation(s)
- Peter Heftberger
- Instiute of Molecular Biosciences, Biophysics Division, University of Graz, Austria
| | - Benjamin Kollmitzer
- Instiute of Molecular Biosciences, Biophysics Division, University of Graz, Austria
| | - Frederick A. Heberle
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Jianjun Pan
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | - Michael Rappolt
- Institute of Inorganic Chemistry, Graz University of Technology, Austria
- School of Food Science and Nutrition, University of Leeds, UK
| | - Heinz Amenitsch
- Institute of Inorganic Chemistry, Graz University of Technology, Austria
| | - Norbert Kučerka
- Canadian Neutron Beam Centre, National Research Council, Chalk River, ON, Canada
| | - John Katsaras
- Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Joint Institute for Neutron Sciences, Oak Ridge, TN, USA
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, USA
- Department of Physics, Brock University, St Catharines, ON, Canada
| | - Georg Pabst
- Instiute of Molecular Biosciences, Biophysics Division, University of Graz, Austria
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Murugova TN, Balgavý P. Molecular volumes of DOPC and DOPS in mixed bilayers of multilamellar vesicles. Phys Chem Chem Phys 2014; 16:18211-6. [DOI: 10.1039/c4cp01980f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Specific volume of 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phospho-l-serine mixtures in bilayers linearly depends on the molar fraction of the constituents, indicating an ideal volume mixing.
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Affiliation(s)
- T. N. Murugova
- Frank Laboratory of Neutron Physics
- Joint Institute for Nuclear Research
- 141980 Dubna, Russia
- Moscow Institute of Physics and Technology
- 141700 Dolgoprudny, Russia
| | - P. Balgavý
- Department of Physical Chemistry of Drugs
- Faculty of Pharmacy
- Comenius University
- 832 32 Bratislava, Slovakia
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25
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Damas C, Carcenac Y, Abarbri M, Coudert R. Synthesis and physicochemical properties of unsaturated trifluoromethylated sodium carboxylates in aqueous media. J Colloid Interface Sci 2013; 395:119-26. [DOI: 10.1016/j.jcis.2012.11.060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 11/27/2012] [Accepted: 11/28/2012] [Indexed: 10/27/2022]
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26
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Structural Versatility of Bicellar Systems and Their Possibilities as Colloidal Carriers. Pharmaceutics 2011; 3:636-64. [PMID: 24310601 PMCID: PMC3857087 DOI: 10.3390/pharmaceutics3030636] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/21/2011] [Accepted: 09/05/2011] [Indexed: 11/17/2022] Open
Abstract
Bicellar systems are lipid nanostructures formed by long- and short-chained phospholipids dispersed in aqueous solution. The morphological transitions of bicellar aggregates due to temperature, composition and time variations have been revised in this work. To this end, two bicellar systems have been considered; one formed by dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC) and another formed by dipalmitoyl-phosphatidylcholine (DPPC) and DHPC. The relationship between the magnetic alignment, the morphology of the aggregates and the phase transition temperature (Tm) of lipids is discussed. In general terms, the non-alignable samples present rounded objects at temperature below the Tm. Above this temperature, an increase of viscosity is followed by the formation of large elongated aggregates. Alignable samples presented discoidal objects below the Tm. The best alignment was achieved above this temperature with large areas of lamellar stacked bilayers and some multilamellar vesicles. The effect of the inclusion of ceramides with different chain lengths in the structure of bicelles is also revised in the present article. A number of physical techniques show that the bicellar structures are affected by both the concentration and the type of ceramide. Systems are able to incorporate 10% mol of ceramides that probably are organized forming domains. The addition of 20% mol of ceramides promotes destabilization of bicelles, promoting the formation of mixed systems that include large structures. Bicellar systems have demonstrated to be morphologically stable with time, able to encapsulate different actives and to induce specific effects on the skin. These facts make bicellar systems good candidates as colloidal carriers for dermal delivery. However, water dilution induces structural changes and formation of vesicular structures in the systems; stabilization strategies have been been explored in recent works and are also updated here.
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Klacsová M, Bulacu M, Kučerka N, Uhríková D, Teixeira J, Marrink S, Balgavý P. The effect of aliphatic alcohols on fluid bilayers in unilamellar DOPC vesicles — A small-angle neutron scattering and molecular dynamics study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2136-46. [DOI: 10.1016/j.bbamem.2011.04.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2010] [Revised: 03/30/2011] [Accepted: 04/21/2011] [Indexed: 10/18/2022]
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Gallová J, Uhríková D, Kučerka N, Svorková M, Funari SS, Murugova TN, Almásy L, Mazúr M, Balgavý P. Influence of cholesterol and β-sitosterol on the structure of EYPC bilayers. J Membr Biol 2011; 243:1-13. [PMID: 21814861 DOI: 10.1007/s00232-011-9387-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 07/13/2011] [Indexed: 11/28/2022]
Abstract
The influence of cholesterol and β-sitosterol on egg yolk phosphatidylcholine (EYPC) bilayers is compared. Different interactions of these sterols with EYPC bilayers were observed using X-ray diffraction. Cholesterol was miscible with EYPC in the studied concentration range (0-50 mol%), but crystallization of β-sitosterol in EYPC bilayers was observed at X ≥ 41 mol% as detected by X-ray diffraction. Moreover, the repeat distance (d) of the lamellar phase was similar upon addition of the two sterols up to mole fraction 17%, while for X ≥ 17 mol% it became higher in the presence of β-sitosterol compared to cholesterol. SANS data on suspensions of unilamellar vesicles showed that both cholesterol and β-sitosterol similarly increase the EYPC bilayer thickness. Cholesterol in amounts above 33 mol% decreased the interlamellar water layer thickness, probably due to "stiffening" of the bilayer. This effect was not manifested by β-sitosterol, in particular due to the lower solubility of β-sitosterol in EYPC bilayers. Applying the formalism of partial molecular areas, it is shown that the condensing effect of both sterols on the EYPC area at the lipid-water interface is small, if any. The parameters of ESR spectra of spin labels localized in different regions of the EYPC bilayer did not reveal any differences between the effects of cholesterol and β-sitosterol in the range of full miscibility.
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Affiliation(s)
- Jana Gallová
- Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, 832 32 Bratislava, Slovakia.
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Kučerka N, Nieh MP, Katsaras J. Fluid phase lipid areas and bilayer thicknesses of commonly used phosphatidylcholines as a function of temperature. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2761-71. [PMID: 21819968 DOI: 10.1016/j.bbamem.2011.07.022] [Citation(s) in RCA: 741] [Impact Index Per Article: 57.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 07/14/2011] [Accepted: 07/15/2011] [Indexed: 10/18/2022]
Abstract
The structural parameters of fluid phase bilayers composed of phosphatidylcholines with fully saturated, mixed, and branched fatty acid chains, at several temperatures, have been determined by simultaneously analyzing small-angle neutron and X-ray scattering data. Bilayer parameters, such as area per lipid and overall bilayer thickness have been obtained in conjunction with intrabilayer structural parameters (e.g. hydrocarbon region thickness). The results have allowed us to assess the effect of temperature and hydrocarbon chain composition on bilayer structure. For example, we found that for all lipids there is, not surprisingly, an increase in fatty acid chain trans-gauche isomerization with increasing temperature. Moreover, this increase in trans-gauche isomerization scales with fatty acid chain length in mixed chain lipids. However, in the case of lipids with saturated fatty acid chains, trans-gauche isomerization is increasingly tempered by attractive chain-chain van der Waals interactions with increasing chain length. Finally, our results confirm a strong dependence of lipid chain dynamics as a function of double bond position along fatty acid chains.
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Affiliation(s)
- Norbert Kučerka
- Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, Canada.
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30
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Gallová J, Uhríková D, Kučerka N, Teixeira J, Balgavý P. Partial area of cholesterol in monounsaturated diacylphosphatidylcholine bilayers. Chem Phys Lipids 2010; 163:765-70. [DOI: 10.1016/j.chemphyslip.2010.08.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Revised: 08/03/2010] [Accepted: 08/12/2010] [Indexed: 11/16/2022]
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31
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Marsh D. Molecular volumes of phospholipids and glycolipids in membranes. Chem Phys Lipids 2010; 163:667-77. [DOI: 10.1016/j.chemphyslip.2010.06.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2010] [Revised: 06/17/2010] [Accepted: 06/17/2010] [Indexed: 12/17/2022]
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32
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Klacsová M, Westh P, Balgavý P. Molecular and component volumes of saturated n-alkanols in DOPC+DOPS bilayers. Chem Phys Lipids 2010; 163:498-505. [DOI: 10.1016/j.chemphyslip.2010.04.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Revised: 04/07/2010] [Accepted: 04/08/2010] [Indexed: 10/19/2022]
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Mannock DA, Lewis RN, McMullen TP, McElhaney RN. The effect of variations in phospholipid and sterol structure on the nature of lipid–sterol interactions in lipid bilayer model membranes. Chem Phys Lipids 2010; 163:403-48. [DOI: 10.1016/j.chemphyslip.2010.03.011] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Revised: 03/13/2010] [Accepted: 03/27/2010] [Indexed: 01/30/2023]
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34
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Kučerka N, Nieh MP, Katsaras J. Small-Angle Scattering from Homogenous and Heterogeneous Lipid Bilayers. ADVANCES IN PLANAR LIPID BILAYERS AND LIPOSOMES 2010. [DOI: 10.1016/b978-0-12-381266-7.00008-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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35
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Kucerka N, Gallová J, Uhríková D, Balgavý P, Bulacu M, Marrink SJ, Katsaras J. Areas of monounsaturated diacylphosphatidylcholines. Biophys J 2009; 97:1926-32. [PMID: 19804723 DOI: 10.1016/j.bpj.2009.06.050] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 06/17/2009] [Accepted: 06/23/2009] [Indexed: 11/17/2022] Open
Abstract
We have studied the structural properties of monounsaturated diacylphosphatidylcholine lipid bilayers (i.e., diCn:1PC, where n = 14, 16, 18, 20, 22, and 24 is the number of acyl chain carbons). High-resolution x-ray scattering data were analyzed in conjunction with contrast-varied neutron scattering data using a technique we recently developed. Analyses of the data show that the manner by which bilayer thickness increases with increasing n in monounsaturated diacylphosphatidylcholines is dependent on the double bond's position. For commonly available monounsaturated diacylphosphatidylcholines, this results in the nonlinear behavior of both bilayer thickness and lipid area, whereas for diC18:1PC bilayers, lipid area assumes a maximum value. It is worthwhile to note that compared to previous data, our results indicate that lipid areas are smaller by approximately 10%. This observation highlights the need to revisit lipid areas, as they are often used in comparisons with molecular dynamics simulations. Moreover, simulators are encouraged to compare their results not only to x-ray scattering data, but to neutron data as well.
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Affiliation(s)
- Norbert Kucerka
- Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, Canada
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36
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Saveyn P, De Geeter J, Sinnaeve D, Van der Meeren P, Martins JC. Influence of the vesicular bilayer structure on the sorption of ethylbenzyl alcohol. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:11322-11327. [PMID: 19722601 DOI: 10.1021/la9005295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The influence of the physicochemical properties of the vesicular bilayer on the sorption of poorly water soluble compounds was investigated with pulsed field gradient 1H nuclear magnetic resonance (PFG-NMR) for the case of phosphatidylcholine and dioctadecyldimethylammonium bromide (DODAB), using 4-ethylbenzyl alcohol as a model compound. Hereby, the effect of bilayer thickness at a constant physicochemical state was studied using a range of phosphatidylcholines of varying chain lengths, whereas DODAB was preferred to check the influence of the bilayer physicochemical state since this cationic lipid is characterized by three different states within the studied temperature range. When the phospholipid alkyl chain length was changed, no differences were observed in the sorption which was linked to the surface-mediated sorption. On the other hand, when the chemical composition was preserved but the temperature and thus the physical state of the bilayer were changed, the sorption in dioctadecyldimethylammonium bromide (DODAB) vesicles changed dramatically. From those experiments, a strong relationship between the ordering of the surfactant molecules and the sorption can be assumed.
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Affiliation(s)
- Pieter Saveyn
- Particle and Interfacial Technology Group, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Gent, Belgium.
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Peters GH, Hansen FY, Møller MS, Westh P. Effects of Fatty Acid Inclusion in a DMPC Bilayer Membrane. J Phys Chem B 2008; 113:92-102. [DOI: 10.1021/jp806205m] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Günther H. Peters
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Flemming Y. Hansen
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Martin S. Møller
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
| | - Peter Westh
- Department of Chemistry, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark; Department of Life Sciences and Chemistry, Roskilde University, 4000 Roskilde, Denmark; and MEMPHYS-Center for Biomembrane Physics
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38
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Hydrophobic thickness, lipid surface area and polar region hydration in monounsaturated diacylphosphatidylcholine bilayers: SANS study of effects of cholesterol and beta-sitosterol in unilamellar vesicles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2008; 1778:2627-32. [PMID: 18782557 DOI: 10.1016/j.bbamem.2008.08.009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 07/31/2008] [Accepted: 08/04/2008] [Indexed: 11/20/2022]
Abstract
The influence of a mammalian sterol cholesterol and a plant sterol beta-sitosterol on the structural parameters and hydration of bilayers in unilamellar vesicles made of monounsaturated diacylphosphatidylcholines (diCn:1PC, n=14-22 is the even number of acyl chain carbons) was studied at 30 degrees C using small-angle neutron scattering (SANS). Recently published advanced model of lipid bilayer as a three-strip structure was used with a triangular shape of polar head group probability distribution (Kucerka et al., Models to analyze small-angle neutron scattering from unilamellar lipid vesicles, Physical Review E 69 (2004) Art. No. 051903). It was found that 33 mol% of both sterols increased the thickness of diCn:1PC bilayers with n=18-22 similarly. beta-sitosterol increased the thickness of diC14:1PC and diC16:1PC bilayers a little more than cholesterol. Both sterols increased the surface area per unit cell by cca 12 A(2) and the number of water molecules located in the head group region by cca 4 molecules, irrespective to the acyl chain length of diCn:1PC. The structural difference in the side chain between cholesterol and beta-sitosterol plays a negligible role in influencing the structural parameters of bilayers studied.
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Lipid bilayer structure determined by the simultaneous analysis of neutron and X-ray scattering data. Biophys J 2008; 95:2356-67. [PMID: 18502796 DOI: 10.1529/biophysj.108.132662] [Citation(s) in RCA: 444] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Quantitative structures were obtained for the fully hydrated fluid phases of dioleoylphosphatidylcholine (DOPC) and dipalmitoylphosphatidylcholine (DPPC) bilayers by simultaneously analyzing x-ray and neutron scattering data. The neutron data for DOPC included two solvent contrasts, 50% and 100% D(2)O. For DPPC, additional contrast data were obtained with deuterated analogs DPPC_d62, DPPC_d13, and DPPC_d9. For the analysis, we developed a model that is based on volume probability distributions and their spatial conservation. The model's design was guided and tested by a DOPC molecular dynamics simulation. The model consistently captures the salient features found in both electron and neutron scattering density profiles. A key result of the analysis is the molecular surface area, A. For DPPC at 50 degrees C A = 63.0 A(2), whereas for DOPC at 30 degrees C A = 67.4 A(2), with estimated uncertainties of 1 A(2). Although A for DPPC agrees with a recently reported value obtained solely from the analysis of x-ray scattering data, A for DOPC is almost 10% smaller. This improved method for determining lipid areas helps to reconcile long-standing differences in the values of lipid areas obtained from stand-alone x-ray and neutron scattering experiments and poses new challenges for molecular dynamics simulations.
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Kucerka N, Pencer J, Nieh MP, Katsaras J. Influence of cholesterol on the bilayer properties of monounsaturated phosphatidylcholine unilamellar vesicles. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2007; 23:247-54. [PMID: 17619814 DOI: 10.1140/epje/i2007-10202-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 05/30/2007] [Indexed: 05/16/2023]
Abstract
The influence of cholesterol on the structure of unilamellar-vesicle (ULV) phospholipid bilayers is studied using small-angle neutron scattering. ULVs made up of short-, mid- and long-chain monounsaturated phospholipids (diCn :1PC, n = 14 , 18, 22, respectively) are examined over a range (0-45 mol %) of cholesterol concentrations. Cholesterol's effect on bilayer structure is characterized through changes to the lipid's transmembrane thickness, lateral area and headgroup hydration. For all three lipids, analysis of the experimental data shows that the addition of cholesterol results in a monotonic increase of these parameters. In the case of the short- and mid-chain lipids, this is an expected result, however, such a finding was unexpected for the long-chain lipid. This implies that cholesterol has a pronounced effect on the lipid's hydrocarbon chain organization.
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Affiliation(s)
- N Kucerka
- Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, Canada.
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