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Zabala-Ferrera O, Liu P, Beltramo PJ. Determining the Bending Rigidity of Free-Standing Planar Phospholipid Bilayers. MEMBRANES 2023; 13:129. [PMID: 36837632 PMCID: PMC9959114 DOI: 10.3390/membranes13020129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/14/2023] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
We describe a method to determine membrane bending rigidity from capacitance measurements on large area, free-standing, planar, biomembranes. The bending rigidity of lipid membranes is an important biological mechanical property that is commonly optically measured in vesicles, but difficult to quantify in a planar, unsupported system. To accomplish this, we simultaneously image and apply an electric potential to free-standing, millimeter area, planar lipid bilayers composed of DOPC and DOPG phospholipids to measure the membrane Young's (elasticity) modulus. The bilayer is then modeled as two adjacent thin elastic films to calculate bending rigidity from the electromechanical response of the membrane to the applied field. Using DOPC, we show that bending rigidities determined by this approach are in good agreement with the existing work using neutron spin echo on vesicles, atomic force spectroscopy on supported lipid bilayers, and micropipette aspiration of giant unilamellar vesicles. We study the effect of asymmetric calcium concentration on symmetric DOPC and DOPG membranes and quantify the resulting changes in bending rigidity. This platform offers the ability to create planar bilayers of controlled lipid composition and aqueous ionic environment, with the ability to asymmetrically alter both. We aim to leverage this high degree of compositional and environmental control, along with the capacity to measure physical properties, in the study of various biological processes in the future.
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2
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Vishvakarma V, Engberg O, Huster D, Maiti S. The effect of cholesterol on highly curved membranes measured by nanosecond Fluorescence Correlation Spectroscopy. Methods Appl Fluoresc 2022; 10. [PMID: 35940167 DOI: 10.1088/2050-6120/ac87ea] [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: 05/18/2022] [Accepted: 08/08/2022] [Indexed: 11/11/2022]
Abstract
Small lipid vesicles (with diameter ≤ 100nm) with their highly curved membranes comprise a special class of biological lipid bilayers. The mechanical properties of such membranes are critical for their function, e.g. exocytosis. Cholesterol is a near-universal regulator of membrane properties in animal cells. Yet measurements of the effect of cholesterol on the mechanical properties of membranes have remained challenging, and the interpretation of such measurements has remained a matter of debate. Here we show that nanosecond fluorescence correlation spectroscopy (FCS) can directly measure the ns-microsecond rotational correlation time (τr) of a lipid probe in high curvature vesicles with extraordinary sensitivity. Using a home-built 4-Pi fluorescence cross-correlation spectrometer containing polarization-modulating elements, we measure the rotational correlation time (τr) of Nile Red in neurotransmitter vesicle mimics. As the cholesterol mole fraction increases from 0 to 50 %, τr increases from 17 ± 1 to 112 ± 12 ns, indicating a viscosity change of nearly a factor of 7. These measurements are corroborated by solid-state NMR results, which show that the order parameter of the lipid acyl chains increases by about 50% for the same change in cholesterol concentration. Additionally, we measured the spectral parameters of polarity-sensitive fluorescence dyes, which provide an indirect measure of viscosity. The green/red ratio of Nile Red and the generalized polarization of Laurdan show consistent increases of 1.3x and 2.6x, respectively. Our results demonstrate that rotational FCS can directly measure the viscosity of highly curved membranes with higher sensitivity and wider dynamic range compared to other conventional techniques. Significantly, we observe that the viscosity of neurotransmitter vesicle mimics is remarkably sensitive to their cholesterol content.
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Affiliation(s)
- Vicky Vishvakarma
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Navy Nagar Colaba, MUMBAI, Mumbai, Maharashtra, 400005, INDIA
| | - Oskar Engberg
- Institut für Medizinische Physik und Biophysik Universität Leipzig, Universität Leipzig Medizinische Fakultät, Härtelstr. 16-18 04107 Leipzig Germany, Leipzig, Sachsen, 04107, GERMANY
| | - Daniel Huster
- Institut für Medizinische Physik und Biophysik, Universität Leipzig Medizinische Fakultät, Härtelstr. 16-18 04107 Leipzig, Leipzig, Sachsen, 04107, GERMANY
| | - Sudipta Maiti
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Navy Nagar Colaba, Mumbai, 400005, INDIA
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3
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Fu M, Franquelim HG, Kretschmer S, Schwille P. Non‐Equilibrium Large‐Scale Membrane Transformations Driven by MinDE Biochemical Reaction Cycles. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202015184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Meifang Fu
- Dept. Cellular and Molecular Biophysics Max Planck Institute of Biochemistry Am Klopferspitz 18 82152 Martinsried Germany
| | - Henri G. Franquelim
- Dept. Cellular and Molecular Biophysics Max Planck Institute of Biochemistry Am Klopferspitz 18 82152 Martinsried Germany
| | - Simon Kretschmer
- Dept. Cellular and Molecular Biophysics Max Planck Institute of Biochemistry Am Klopferspitz 18 82152 Martinsried Germany
- Department of Bioengineering and Therapeutic Science University of California San Francisco San Francisco CA USA
| | - Petra Schwille
- Dept. Cellular and Molecular Biophysics Max Planck Institute of Biochemistry Am Klopferspitz 18 82152 Martinsried Germany
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4
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Fu M, Franquelim HG, Kretschmer S, Schwille P. Non-Equilibrium Large-Scale Membrane Transformations Driven by MinDE Biochemical Reaction Cycles. Angew Chem Int Ed Engl 2021; 60:6496-6502. [PMID: 33285025 PMCID: PMC7986748 DOI: 10.1002/anie.202015184] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Indexed: 12/11/2022]
Abstract
The MinDE proteins from E. coli have received great attention as a paradigmatic biological pattern-forming system. Recently, it has surfaced that these proteins do not only generate oscillating concentration gradients driven by ATP hydrolysis, but that they can reversibly deform giant vesicles. In order to explore the potential of Min proteins to actually perform mechanical work, we introduce a new model membrane system, flat vesicle stacks on top of a supported lipid bilayer. MinDE oscillations can repeatedly deform these flat vesicles into tubules and promote progressive membrane spreading through membrane adhesion. Dependent on membrane and buffer compositions, Min oscillations further induce robust bud formation. Altogether, we demonstrate that under specific conditions, MinDE self-organization can result in work performed on biomimetic systems and achieve a straightforward mechanochemical coupling between the MinDE biochemical reaction cycle and membrane transformation.
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Affiliation(s)
- Meifang Fu
- Dept. Cellular and Molecular BiophysicsMax Planck Institute of BiochemistryAm Klopferspitz 1882152MartinsriedGermany
| | - Henri G. Franquelim
- Dept. Cellular and Molecular BiophysicsMax Planck Institute of BiochemistryAm Klopferspitz 1882152MartinsriedGermany
| | - Simon Kretschmer
- Dept. Cellular and Molecular BiophysicsMax Planck Institute of BiochemistryAm Klopferspitz 1882152MartinsriedGermany
- Department of Bioengineering and Therapeutic ScienceUniversity of California San FranciscoSan FranciscoCAUSA
| | - Petra Schwille
- Dept. Cellular and Molecular BiophysicsMax Planck Institute of BiochemistryAm Klopferspitz 1882152MartinsriedGermany
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5
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de Lange N, Kleijn JM, Leermakers FAM. Structural and mechanical parameters of lipid bilayer membranes using a lattice refined self-consistent field theory. Phys Chem Chem Phys 2021; 23:5152-5175. [PMID: 33624676 DOI: 10.1039/d0cp05597b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The self-consistent field theory of Scheutjens and Fleer is implemented on a grid with (lattice) sites that are smaller than the segment size. In this quasi lattice-free implementation we consider united atom-like molecular models and study bilayer self-assembly of phospholipids in a selective solvent (water). We find structural as well as mechanical parameters for these bilayers. The mean (κ) and Gaussian ([small kappa, Greek, macron]) bending moduli, as well as the spontaneous curvature of the monolayer (Jm0), are computed for the first time following a grand canonical ensemble route. Results are in line with previous estimates for mechanical parameters that at the time could not be made following this correct route. This proves that the mean bending modulus is only a very weak function of the membrane tension. We performed a systematic study on the effects of model parameter variations. The mean bending modulus generally grows with increasing bilayer thickness. As expected Jm0 and [small kappa, Greek, macron] behave oppositely with respect to each other and for classical phospholipids assumes values near zero. As an example, an increase in the lipophilic to hydrophilic ratio in the lipids, may cause the Gaussian bending rigidity to switch sign from negative to positive, while - not necessarily at the same point - the spontaneous curvature of the monolayer may switch sign from positive to negative. Together with other investigated trends, these results point to mechanisms of how topological phase transitions of the lipid bilayer membranes may be regulated in the biological context, which correlates with known lipid phase behaviour.
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Affiliation(s)
- N de Lange
- Physical Chemistry and Soft Matter, Wageningen University & Research Center, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - J M Kleijn
- Physical Chemistry and Soft Matter, Wageningen University & Research Center, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
| | - F A M Leermakers
- Physical Chemistry and Soft Matter, Wageningen University & Research Center, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
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6
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Karal MAS, Ahmed M, Levadny V, Belaya M, Ahamed MK, Rahman M, Shakil MM. Electrostatic interaction effects on the size distribution of self-assembled giant unilamellar vesicles. Phys Rev E 2020; 101:012404. [PMID: 32069606 DOI: 10.1103/physreve.101.012404] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2019] [Indexed: 12/26/2022]
Abstract
The influence of electrostatic conditions (salt concentration of the solution and vesicle surface charge density) on the size distribution of self-assembled giant unilamellar vesicles (GUVs) is considered. The membranes of GUVs are synthesized by a mixture of dioleoylphosphatidylglycerol and dioleoylphosphatidylcholine in a physiological buffer using the natural swelling method. The experimental results are presented in the form of a set of histograms. The log-normal distribution is used for statistical treatment of results. It is obtained that the decrease of salt concentration and the increase of vesicle surface charge density of the membranes increase the average size of the GUV population. To explain the experimental results, a theory using the Helmholtz free energy of the system describing the GUV vesiculation is developed. The size distribution histograms and average size of GUVs under various conditions are fitted with the proposed theory. It is shown that the variation of the bending modulus due to changing of electrostatic parameters of the system is the main factor causing a change in the average size of GUVs.
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Affiliation(s)
- Mohammad Abu Sayem Karal
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
| | - Marzuk Ahmed
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
| | - Victor Levadny
- Theoretical Problem Center of Physico-Chemical Pharmacology, Russian Academy of Sciences, Moscow 117977, Russia
| | - Marina Belaya
- Department of Mathematics of Russian State University for the Humanities, Moscow GSP-3 125993, Russia
| | - Md Kabir Ahamed
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
| | - Mostafizur Rahman
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
| | - Md Mostofa Shakil
- Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh
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7
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Fink L, Steiner A, Szekely O, Szekely P, Raviv U. Structure and Interactions between Charged Lipid Membranes in the Presence of Multivalent Ions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:9694-9703. [PMID: 31283884 DOI: 10.1021/acs.langmuir.9b00778] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
When aqueous salt solutions contain multivalent ions (like Ca2+ or Mg2+), strong correlation effects may lead to ion-bridging, net attraction, and tight-coupling between like-charged interfaces. To examine the effects of surface charge density, temperature, salt type, and salt concentration on the structures of tightly coupled charged interfaces, we have used mixed lipid membranes, containing either saturated or unsaturated tails in the presence of multivalent ions. We discovered that tightly coupled membrane lamellar phases, dominated by attractive interactions, coexisted with weakly coupled lamellar phases, dominated by repulsive interactions. To control the membrane charge density, we mixed lipids with negatively charged headgroups, DLPS and DOPS, with their zwitterionic analogue having the same tails, DLPC and DOPC, respectively. Using solution X-ray scattering we measured the lamellar repeat distance, D, at different ion concentrations, temperatures, and membrane charge densities. The multivalent ions tightly coupled the mixed lipid bilayers whose charged lipid molar fraction was between 0.1 and 1. The repeat distance of the tightly coupled phase was about 4 nm for the DLPS/DLPC mixtures and about 5 nm for the DOPS/DOPC mixtures. In this phase, the repeat distance slightly increased with increasing temperature and decreased with increasing charge density. When the molar fraction of charged lipid was 0.1 or 0.25, a less tightly coupled phase coexisted with the tightly coupled phase. The weakly coupled lamellar phase had significantly larger D values, although they were consistently shorter than the D values in monovalent salt solutions with similar screening lengths.
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Affiliation(s)
- Lea Fink
- Institute of Chemistry and Center for Nanoscience and Nanotechnology, Edmond J. Safra Campus, Givat Ram , The Hebrew University of Jerusalem , Jerusalem , 9190401 , Israel
| | - Ariel Steiner
- Institute of Chemistry and Center for Nanoscience and Nanotechnology, Edmond J. Safra Campus, Givat Ram , The Hebrew University of Jerusalem , Jerusalem , 9190401 , Israel
| | - Or Szekely
- Institute of Chemistry and Center for Nanoscience and Nanotechnology, Edmond J. Safra Campus, Givat Ram , The Hebrew University of Jerusalem , Jerusalem , 9190401 , Israel
| | - Pablo Szekely
- Institute of Chemistry and Center for Nanoscience and Nanotechnology, Edmond J. Safra Campus, Givat Ram , The Hebrew University of Jerusalem , Jerusalem , 9190401 , Israel
| | - Uri Raviv
- Institute of Chemistry and Center for Nanoscience and Nanotechnology, Edmond J. Safra Campus, Givat Ram , The Hebrew University of Jerusalem , Jerusalem , 9190401 , Israel
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8
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Zhang M, Corona PT, Ruocco N, Alvarez D, Malo de Molina P, Mitragotri S, Helgeson ME. Controlling Complex Nanoemulsion Morphology Using Asymmetric Cosurfactants for the Preparation of Polymer Nanocapsules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:978-990. [PMID: 29087721 DOI: 10.1021/acs.langmuir.7b02843] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Complex nanoemulsions, comprising multiphase nanoscale droplets, hold considerable potential advantages as vehicles for encapsulation and delivery as well as templates for nanoparticle synthesis. Although methods exist to controllably produce complex emulsions on the microscale, very few methods exist to produce them on the nanoscale. Here, we examine a recently developed method involving a combination of high-energy emulsification with conventional cosurfactants to produce oil-water-oil (O/W/O) complex nanoemulsions. Specifically, we study in detail how the composition of conventional ethoxylated cosurfactants Span80 and Tween20 influences the morphology and structure of the resulting complex nanoemulsions in the water-cyclohexane system. Using a combination of small-angle neutron scattering and cryo-electron microscopy, we find that the cosurfactant composition controls the generation of complex droplet morphologies including core-shell and multicore-shell O/W/O nanodroplets, resulting in an effective state diagram for the selection of nanoemulsion morphology. Additionally, the cosurfactant composition can be used to control the thickness of the water shell contained within the complex nanodroplets. We hypothesize that this degree of control, despite the highly nonequilibrium nature of the nanoemulsions, is ultimately determined by a competition between the opposing spontaneous curvature of the two cosurfactants, which strongly influences the interfacial curvature of the nanodroplets as a result of their ultralow interfacial tension. This is supported by a correlation between cosurfactant compositions that produces complex nanoemulsions and those that produce homogeneous mixed micelles in equilibrium surfactant-cyclohexane solutions. Ultimately, we show that the formation of complex O/W/O nanoemulsions is weakly perturbed upon the addition of hydrophilic polymer precursors, facilitating their use as templates for the formation of polymer nanocapsules.
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Affiliation(s)
- Mengwen Zhang
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Patrick T Corona
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Nino Ruocco
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
| | - David Alvarez
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Paula Malo de Molina
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Samir Mitragotri
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
| | - Matthew E Helgeson
- Department of Chemical Engineering, University of California , Santa Barbara, California 93106, United States
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9
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Zheng Y, Liu X, Samoshina NM, Samoshin VV, Franz AH, Guo X. Fliposomes: trans-2-aminocyclohexanol-based amphiphiles as pH-sensitive conformational switches of liposome membrane - a structure-activity relationship study. Chem Phys Lipids 2017; 210:129-141. [PMID: 29111431 DOI: 10.1016/j.chemphyslip.2017.10.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 10/10/2017] [Accepted: 10/11/2017] [Indexed: 01/20/2023]
Abstract
Recently developed lipids with the trans-2-aminocyclohexanol (TACH) moiety represent unique pH-sensitive conformational switches ("flipids") that can trigger the membrane of liposome-based drug delivery systems at lowered pH as seen in many pathological scenarios. A library of flipids with various TACH-based headgroups and hydrocarbon tails were designed, prepared, and characterized to systematically elucidate the relationship between their chemical structures and their ability to form and to trigger liposomes. Liposomes (fliposomes) consisting of a flipid, POPC and PEG-ceramide were stable at 4°C, pH 7.4 for up to several months and yet released the encapsulated fluorophore in seconds upon acidification. The colloidal properties and encapsulation efficiencies of the fliposomes depended on the structure features of the flipids such as the polarity of the headgroups and the shape and fluidity of the lipid tails. The pH-triggered release also depended on the flipid structure, where shorter linear tails yielded more efficient release. The release of fliposomes was enhanced at different narrow pH ranges, depending on the basicity of the flipid headgroup, which can be estimated either by calculated pKa or by acid/base titration of the flipids while its conformation is monitored by 1H NMR. The structure-activity relationship of the flipids supports "lipid tail conformational shortening" as the mechanism to disrupt lipid membranes and would provide great flexibility in the design of pH-sensitive drug delivery systems.
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Affiliation(s)
- Yu Zheng
- Department of Chemistry, College of the Pacific, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA; Department of Pharmaceutics and Medicinal Chemistry, Thomas J Long School of Pharmacy and Health Sciences, University of the Pacific, 751 Brookside Road, Stockton, CA 95211, USA
| | - Xin Liu
- Department of Chemistry, College of the Pacific, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA
| | - Nataliya M Samoshina
- Department of Chemistry, College of the Pacific, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA; Department of Pharmaceutics and Medicinal Chemistry, Thomas J Long School of Pharmacy and Health Sciences, University of the Pacific, 751 Brookside Road, Stockton, CA 95211, USA
| | - Vyacheslav V Samoshin
- Department of Chemistry, College of the Pacific, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA.
| | - Andreas H Franz
- Department of Chemistry, College of the Pacific, University of the Pacific, 3601 Pacific Avenue, Stockton, CA 95211, USA
| | - Xin Guo
- Department of Pharmaceutics and Medicinal Chemistry, Thomas J Long School of Pharmacy and Health Sciences, University of the Pacific, 751 Brookside Road, Stockton, CA 95211, USA.
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10
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Formation of planar unilamellar phospholipid membranes on oxidized gold substrate. Biointerphases 2016; 11:031017. [DOI: 10.1116/1.4963188] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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11
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Srivastava A, Voth GA. Solvent-Free, Highly Coarse-Grained Models for Charged Lipid Systems. J Chem Theory Comput 2014; 10:4730-4744. [PMID: 25328498 PMCID: PMC4196741 DOI: 10.1021/ct500474a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Indexed: 12/13/2022]
Abstract
![]()
We
present a methodology to develop coarse-grained lipid models
such that electrostatic interactions between the coarse-grained sites
can be derived accurately from an all-atom molecular dynamics trajectory
and expressed as an effective pairwise electrostatic potential with
appropriate screening functions. The reference nonbonded forces from
the all-atom trajectory are decomposed into separate electrostatic
and van der Waals (vdW) forces, based on the multiscale coarse-graining
method. The coarse-grained electrostatic potential is assumed to be
a general function of unknown variables and the final site–site
interactions are obtained variationally, where the residual of the
electrostatic forces from the assumed field is minimized. The resulting
electrostatic interactions are fitted to screened electrostatics functions,
with a special treatment for distance-dependent dielectrics and screened
dipole–dipole interactions. The vdW interactions are derived
separately. The resulting charged hybrid coarse-graining method is
applied to various solvent-free three-site models of anionic lipid
systems.
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Affiliation(s)
- Anand Srivastava
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, and Computation Institute, The University of Chicago , 5735 S. Ellis Ave., Chicago, Illinois 60637, United States
| | - Gregory A Voth
- Department of Chemistry, Institute for Biophysical Dynamics, James Franck Institute, and Computation Institute, The University of Chicago , 5735 S. Ellis Ave., Chicago, Illinois 60637, United States
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12
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Pannuzzo M, Raudino A, Böckmann RA. Peptide-induced membrane curvature in edge-stabilized open bilayers: A theoretical and molecular dynamics study. J Chem Phys 2014; 141:024901. [DOI: 10.1063/1.4885340] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Martina Pannuzzo
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Antonio Raudino
- Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6, 95125 Catania, Italy
| | - Rainer A. Böckmann
- Computational Biology, Department of Biology, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany
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13
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Pera H, Kleijn JM, Leermakers FAM. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling. J Chem Phys 2014; 140:065102. [DOI: 10.1063/1.4863994] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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14
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Leermakers FAM. Bending rigidities of surfactant bilayers using self-consistent field theory. J Chem Phys 2013; 138:154109. [PMID: 23614414 DOI: 10.1063/1.4801327] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Self-consistent field (SCF) theory is used to find bending moduli of surfactant and lipid bilayers. Recently, we successfully applied low-memory search methods to solve the SCF equations. Using these we are now able to directly evaluate the Gaussian bending modulus for molecularly detailed models of bilayers by evaluating the excess Helmholtz energy of tensionless bilayers in a (part of the) Im3m cubic phase. The result prompted us to reconsider the protocol that has been used thus far to find the mean bending modulus kc and Gaussian bending modulus k[overline]. With respect to previous predictions, the value of kc is reduced by a factor of two and the Gaussian bending modulus is less negative and much closer to zero. In line with experimental data we now find that k[overline] can also become positive. In this paper we use the non-ionic surfactants series of the type CnEm for illustration.
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Affiliation(s)
- F A M Leermakers
- Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Dreijenplein 6, Wageningen 6703 HB, The Netherlands
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15
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Srivastava A, Voth GA. A Hybrid Approach for Highly Coarse-grained Lipid Bilayer Models. J Chem Theory Comput 2012; 9:750-765. [PMID: 25100925 DOI: 10.1021/ct300751h] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We present a systematic methodology to develop highly coarse-grained (CG) lipid models for large scale bio-membrane simulations, in which we derive CG interactions using a powerful combination of the multiscale coarse-graining (MS-CG) method, and an analytical form of the CG potential to model interactions at short range. The resulting hybrid coarse-graining (HCG) methodology is used to develop a three-site solvent-free model for 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and a 1:1 mixture of 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) and DOPC. In addition, we developed a four-site model of DOPC, demonstrating the capability of the HCG methodology in designing model lipid systems of a desired resolution. We carried out microsecond-scale molecular dynamics (MD) simulations of large vesicles, highlighting the ability of the model to study systems at mesoscopic length and time scales. The models of DLPC, DOPC and DOPC-DOPS have elastic properties consistent with experiment and structural properties such as the radial distribution functions (RDF), bond and angle distributions, and the z-density distributions that compare well with reference all-atom systems.
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Affiliation(s)
- Anand Srivastava
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics and Computation Institute, University of Chicago, 5735 S. Ellis Ave., Chicago, Illinois 60637, USA
| | - Gregory A Voth
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics and Computation Institute, University of Chicago, 5735 S. Ellis Ave., Chicago, Illinois 60637, USA
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16
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Shi D, Sfintes G, Laursen BW, Simonsen JB. Fluorescent and highly stable unimodal DMPC based unilamellar vesicles formed by spontaneous curvature. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:8608-8615. [PMID: 22594640 DOI: 10.1021/la301454y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The formation of uniform and highly stable unilamellar vesicles (ULVs) and the theory behind it are ongoing tasks within the vesicle community. Herein, we report the formation of highly stable, fluorescent, and unimodal 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) based ULVs with an average size of ~100 nm, as determined by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). The ULVs are formed by mixing a two-component powder mixture or mixed lipid film of DMPC and 5 mol % of a novel amphiphilic carbenium salt, sodium 2-didecylamino-6,10-bis(N-methyltaruino)-4,8,12-trioxatriangulenium (Na-DSA) in aqueous solution when subjected to shaking. We propose that the high stability and the unimodal size distribution of the 5% DSA ULVs confirmed by DLS studies are a product of spontaneous curvature. UV-vis absorption/emission studies reveal that the structure of DSA promotes a strong interaction between the DMPC and the DSA to take place due to the complementary charge distribution of the DSA and DMPC head groups. The strong interaction may introduce an asymmetric amphiphile composition in the inner and outer leaflet of the bilayer which drives the spontaneous curvature.
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Affiliation(s)
- Dong Shi
- Nano-Science Center & Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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Steiner A, Szekely P, Szekely O, Dvir T, Asor R, Yuval-Naeh N, Keren N, Kesselman E, Danino D, Resh R, Ginsburg A, Guralnik V, Feldblum E, Tamburu C, Peres M, Raviv U. Entropic attraction condenses like-charged interfaces composed of self-assembled molecules. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2012; 28:2604-2613. [PMID: 22191627 DOI: 10.1021/la203540p] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Like-charged solid interfaces repel and separate from one another as much as possible. Charged interfaces composed of self-assembled charged-molecules such as lipids or proteins are ubiquitous. The present study shows that although charged lipid-membranes are sufficiently rigid, in order to swell as much as possible, they deviate markedly from the behavior of typical like-charged solids when diluted below a critical concentration (ca. 15 wt %). Unexpectedly, they swell into lamellar structures with spacing that is up to four times shorter than the layers should assume (if filling the entire available space). This process is reversible with respect to changing the lipid concentration. Additionally, the research shows that, although the repulsion between charged interfaces increases with temperature, like-charged membranes, remarkably, condense with increasing temperature. This effect is also shown to be reversible. Our findings hold for a wide range of conditions including varying membrane charge density, bending rigidity, salt concentration, and conditions of typical living systems. We attribute the limited swelling and condensation of the net repulsive interfaces to their self-assembled character. Unlike solids, membranes can rearrange to gain an effective entropic attraction, which increases with temperature and compensates for the work required for condensing the bilayers. Our findings provide new insight into the thermodynamics and self-organization of like-charged interfaces composed of self-assembled molecules such as charged biomaterials and supramolecular assemblies that are widely found in synthetic and natural constructs.
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Affiliation(s)
- Ariel Steiner
- The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel
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18
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Szekely O, Steiner A, Szekely P, Amit E, Asor R, Tamburu C, Raviv U. The structure of ions and zwitterionic lipids regulates the charge of dipolar membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:7419-7438. [PMID: 21598965 DOI: 10.1021/la200264s] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In pure water, zwitterionic lipids form lamellar phases with an equilibrium water gap on the order of 2 to 3 nm as a result of the dominating van der Waals attraction between dipolar bilayers. Monovalent ions can swell those neutral lamellae by a small amount. Divalent ions can adsorb onto dipolar membranes and charge them. Using solution X-ray scattering, we studied how the structure of ions and zwitterionic lipids regulates the charge of dipolar membranes. We found that unlike monovalent ions that weakly interact with all of the examined dipolar membranes, divalent and trivalent ions adsorb onto membranes containing lipids with saturated tails, with an association constant on the order of ∼10 M(-1). One double bond in the lipid tail is sufficient to prevent divalent ion adsorption. We suggest that this behavior is due to the relatively loose packing of lipids with unsaturated tails that increases the area per lipid headgroup, enabling their free rotation. Divalent ion adsorption links two lipids and limits their free rotation. The ion-dipole interaction gained by the adsorption of the ions onto unsaturated membranes is insufficient to compensate for the loss of headgroup free-rotational entropy. The ion-dipole interaction is stronger for cations with a higher valence. Nevertheless, polyamines behave as monovalent ions near dipolar interfaces in the sense that they interact weakly with the membrane surface, whereas in the bulk their behavior is similar to that of multivalent cations. Advanced data analysis and comparison with theory provide insight into the structure and interactions between ion-induced regulated charged interfaces. This study models biologically relevant interactions between cell membranes and various ions and the manner in which the lipid structure governs those interactions. The ability to monitor these interactions creates a tool for probing systems that are more complex and forms the basis for controlling the interactions between dipolar membranes and charged proteins or biopolymers for encapsulation and delivery applications.
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Affiliation(s)
- Or Szekely
- The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904 Jerusalem, Israel
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Raudino A, Pannuzzo M. Adhesion Kinetics between a Membrane and a Flat Substrate. An Ideal Upper Bound to the Spreading Rate of an Adhesive Patch. J Phys Chem B 2010; 114:15495-505. [DOI: 10.1021/jp106722w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Antonio Raudino
- Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6-95125, Catania, Italy
| | - Martina Pannuzzo
- Dipartimento di Scienze Chimiche, Università di Catania, Viale A. Doria 6-95125, Catania, Italy
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Raudino A, Pannuzzo M. Nucleation theory with delayed interactions: An application to the early stages of the receptor-mediated adhesion/fusion kinetics of lipid vesicles. J Chem Phys 2010; 132:045103. [DOI: 10.1063/1.3290823] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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21
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Mechler A, Praporski S, Piantavigna S, Heaton SM, Hall KN, Aguilar MI, Martin LL. Structure and homogeneity of pseudo-physiological phospholipid bilayers and their deposition characteristics on carboxylic acid terminated self-assembled monolayers. Biomaterials 2008; 30:682-9. [PMID: 19000635 DOI: 10.1016/j.biomaterials.2008.10.016] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Accepted: 10/21/2008] [Indexed: 11/13/2022]
Abstract
Supported phospholipid bilayers are frequently used to establish a pseudo-physiological environment required for the study of protein function or the design of enzyme-based biosensors and biocatalytic reactors. These membranes are deposited from bilayer vesicles (liposomes) that rupture and fuse into a planar membrane upon adhesion to a surface. However, the morphology and homogeneity of the resulting layer is affected by the characteristics of the precursor liposome suspension and the substrate. Here we show that two distinct liposome populations contribute to membrane formation--equilibrium liposomes and small unilamellar vesicles. Liposome deposition onto carboxylic acid terminated self-assembled monolayers resulted in planar mono- and multilayer, vesicular and composite membranes, as a function of liposome size and composition. Quartz crystal microbalance data provided estimates for layer thicknesses and sheer moduli and were used for classification of the final structure. Finally, atomic force microscopy data illustrated the inherently inhomogeneous and dynamic nature of these membranes.
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Affiliation(s)
- Adam Mechler
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
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