Molecular mechanisms of spontaneous curvature and softening in complex lipid bilayer mixtures

Published:August 03, 2022DOI:


      Membrane reshaping is an essential biological process. The chemical composition of lipid membranes determines their mechanical properties and thus the energetics of their shape. Hundreds of distinct lipid species make up native bilayers, and this diversity complicates efforts to uncover what compositional factors drive membrane stability in cells. Simplifying assumptions, therefore, are used to generate quantitative predictions of bilayer dynamics based on lipid composition. One assumption commonly used is that “per lipid” mechanical properties are both additive and constant—that they are an intrinsic property of lipids independent of the surrounding composition. Related to this is the assumption that lipid bulkiness, or “shape,” determines its curvature preference, independently of context. In this study, all-atom molecular dynamics simulations on three separate multilipid systems were used to explicitly test these assumptions, applying methodology recently developed to isolate properties of single lipids or nanometer-scale patches of lipids. The curvature preference experienced by populations of lipid conformations were inferred from their redistribution on a dynamically fluctuating bilayer. Representative populations were extracted by both structural similarity and semi-automated hidden Markov model analysis. The curvature preferences of lipid dimers were then determined and compared with an additive model that combines the monomer curvature preference of both the individual lipids. In all three systems, we identified conformational subpopulations of lipid dimers that showed non-additive curvature preference, in each case mediated by a special chemical interaction (e.g., hydrogen bonding). Our study highlights the importance of specific chemical interactions between lipids in multicomponent bilayers and the impact of interactions on bilayer stiffness. We identify two mechanisms of bilayer softening: diffusional softening, driven by the dynamic coupling between lipid distributions and membrane undulations, and conformational softening, driven by the inter-conversion between distinct dimeric conformations.
      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Biophysical Journal
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Harayama T.
        • Riezman H.
        Understanding the diversity of membrane lipid composition.
        Nat. Rev. Mol. Cell Biol. 2018; 19: 281-296
        • Dennis E.A.
        • Norris P.C.
        Eicosanoid storm in infection and inflammation.
        Nat. Rev. Immunol. 2015; 15: 511-523
        • Fernandis A.Z.
        • Wenk M.R.
        Membrane lipids as signaling molecules.
        Curr. Opin. Lipidol. 2007; 18: 121-128
        • Mandal K.
        Review of PIP2 in cellular signaling, functions and diseases.
        Int. J. Mol. Sci. 2020;
        • Van Meer G.
        • Voelker D.R.
        • Feigenson G.W.
        Membrane lipids: where they are and how they behave.
        Nat. Rev. Mol. Cell Biol. 2008; 9: 112-124
        • Lujan P.
        • Campelo F.
        Should I stay or should I go? Golgi membrane spatial organization for protein sorting and retention.
        Arch. Biochem. Biophys. 2021; 707: 108921
        • Nakamura M.T.
        • Yudell B.E.
        • Loor J.J.
        Regulation of energy metabolism by long-chain fatty acids.
        Prog. Lipid Res. 2014; 53: 124-144
        • Deevska G.M.
        • Nikolova-Karakashian M.N.
        The expanding role of sphingolipids in lipid droplet biogenesis.
        Biochim. Biophys. Acta. Mol. Cell Biol. Lipids. 2017; 1862: 1155-1165
        • Lorent J.H.
        • Levental K.R.
        • Levental I.
        • et al.
        Plasma membranes are asymmetric in lipid unsaturation, packing and protein shape.
        Nat. Chem. Biol. 2020; 16: 644-652
        • Levental I.
        • Veatch S.
        The continuing mystery of lipid rafts.
        J. Mol. Biol. 2016; 428: 4749-4764
        • Cheng X.
        • Smith J.C.
        Biological membrane organization and cellular signaling.
        Chem. Rev. 2019; 119: 5849-5880
        • Stone M.B.
        • Shelby S.A.
        • Veatch S.L.
        • et al.
        Protein sorting by lipid phase-like domains supports emergent signaling function in b lymphocyte plasma membranes.
        Elife. 2017; 6: e19891
        • Soubias O.
        • Teague W.E.
        • Gawrisch K.
        • et al.
        Contribution of membrane elastic energy to rhodopsin function.
        Biophys. J. 2010; 99: 817-824
        • Beaven A.H.
        • Maer A.M.
        • Im W.
        • et al.
        Gramicidin A channel formation induces local lipid redistribution I: experiment and simulation.
        Biophys. J. 2017; 112: 1185-1197
        • Brown M.F.
        Curvature forces in membrane lipid-protein interactions.
        Biochemistry. 2012; 51: 9782-9795
        • Steinkühler J.
        • Sezgin E.
        • Dimova R.
        • et al.
        Mechanical properties of plasma membrane vesicles correlate with lipid order, viscosity and cell density.
        Commun. Biol. 2019; 2: 337
        • Gracià R.S.
        • Bezlyepkina N.
        • Dimova R.
        • et al.
        Effect of cholesterol on the rigidity of saturated and unsaturated membranes: fluctuation and electrodeformation analysis of giant vesicles.
        Soft Matter. 2010; 6: 1472-1482
        • Semrau S.
        • Idema T.
        • Storm C.
        • et al.
        Accurate determination of elastic parameters for multicomponent membranes.
        Phys. Rev. Lett. 2008; 100: 088101
        • Needham D.
        • Nunn R.S.
        Elastic deformation and failure of lipid bilayer membranes containing cholesterol.
        Biophys. J. 1990; 58: 997-1009
        • Leibler S.
        Curvature instability in membranes.
        J. Phys. France. 1986; 47: 507-516
        • Sapp K.C.
        • Beaven A.H.
        • Sodt A.J.
        Spatial extent of a single lipid’s influence on bilayer mechanics.
        Phys. Rev. E. 2021; 103: 042413
        • Kozlov M.M.
        • Helfrich W.
        Effects of a cosurfactant on the stretching and bending elasticities of a surfactant monolayer.
        Langmuir. 1992; 8: 2792-2797
        • Bivas I.
        • Méléard P.
        Bending elasticity and bending fluctuations of lipid bilayer containing an additive.
        Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 2003; 67: 012901
        • Tian A.
        • Capraro B.R.
        • Baumgart T.
        • et al.
        Bending stiffness depends on curvature of ternary lipid mixture tubular membranes.
        Biophys. J. 2009; 97: 1636-1646
        • Bashkirov P.V.
        • Kuzmin P.I.
        • Frolov V.A.
        • et al.
        Molecular shape solution for mesoscopic remodeling of cellular membranes.
        Annu. Rev. Biophys. 2022; 51: 473-497
        • Helfrich W.
        Elastic properties of lipid bilayers: theory and possible experiments.
        Z. Naturforsch. C. 1973; 28: 693-703
        • Canham P.B.
        The minimum energy of bending as a possible explanation of the biconcave shape of the human red blood cell.
        J. Theor. Biol. 1970; 26: 61-81
        • Chen Z.
        • Rand R.P.
        The influence of cholesterol on phospholipid membrane curvature and bending elasticity.
        Biophys. J. 1997; 73: 267-276
        • Kaltenegger M.
        • Kremser J.
        • Pabst G.
        • et al.
        Intrinsic lipid curvatures of mammalian plasma membrane outer leaflet lipids and ceramides.
        Biochim. Biophys. Acta Biomembr. 2021; 1863: 183709
        • Sodt A.J.
        • Venable R.M.
        • Pastor R.W.
        • et al.
        Nonadditive compositional curvature energetics of lipid bilayers.
        Phys. Rev. Lett. 2016; 117: 138104
        • Chodera J.D.
        • Noé F.
        Markov state models of biomolecular conformational dynamics.
        Curr. Opin. Struct. Biol. 2014; 25: 135-144
        • Voelz V.A.
        • Jäger M.
        • Pande V.S.
        • et al.
        Slow unfolded-state structuring in acyl-CoA binding protein folding revealed by simulation and experiment.
        J. Am. Chem. Soc. 2012; 134: 12565-12577
        • Voelz V.A.
        • Bowman G.R.
        • Pande V.S.
        • et al.
        Molecular simulation of ab initio protein folding for a millisecond folder NTL9(1-39).
        J. Am. Chem. Soc. 2010; 132: 1526-1528
        • Noé F.
        • Schütte C.
        • Weikl T.R.
        • et al.
        Constructing the equilibrium ensemble of folding pathways from short off-equilibrium simulations.
        Proc. Natl. Acad. Sci. USA. 2009; 106: 19011-19016
        • Lane T.J.
        • Bowman G.R.
        • Pande V.S.
        • et al.
        Markov State model reveals folding and functional dynamics in ultra-long MD trajectories.
        J. Am. Chem. Soc. 2011; 133: 18413-18419
        • Bowman G.R.
        • Pande V.S.
        Protein folded states are kinetic hubs.
        Proc. Natl. Acad. Sci. USA. 2010; 107: 10890-10895
        • Paul F.
        • Wehmeyer C.
        • Noé F.
        • et al.
        Protein-peptide association kinetics beyond the seconds timescale from atomistic simulations.
        Nat. Commun. 2017; 8: 1095
        • Plattner N.
        • Doerr S.
        • Noé F.
        • et al.
        Complete protein-protein association kinetics in atomic detail revealed by molecular dynamics simulations and Markov modelling.
        Nat. Chem. 2017; 9: 1005-1011
        • Sodt A.J.
        • Sandar M.L.
        • Lyman E.
        • et al.
        The molecular structure of the liquid-ordered phase of lipid bilayers.
        J. Am. Chem. Soc. 2014; 136: 725-732
        • Frisz J.F.
        • Klitzing H.A.
        • Kraft M.L.
        • et al.
        Sphingolipid domains in the plasma membranes of fibroblasts are not enriched with cholesterol.
        J. Biol. Chem. 2013; 288: 16855-16861
        • Klauda J.B.
        • Venable R.M.
        • Pastor R.W.
        • et al.
        Update of the CHARMM all-atom additive force field for lipids: validation on six lipid types.
        J. Phys. Chem. B. 2010; 114: 7830-7843
        • Phillips J.C.
        • Braun R.
        • Schulten K.
        • et al.
        Scalable molecular dynamics with NAMD.
        J. Comput. Chem. 2005; 26: 1781-1802
        • Case D.A.
        • Cheatham T.E.
        • Woods R.J.
        • et al.
        The Amber biomolecular simulation programs.
        J. Comput. Chem. 2005; 26: 1668-1688
        • Case D.A.
        • Ben-Shalom I.Y.
        • Gilson M.K.
        • et al.
        Amber 2018.
        University of California, 2018
        • Gomez Y.K.
        • Natale A.M.
        • Grabe M.
        • et al.
        Taking the Monte-Carlo gamble: how not to buckle under the pressure!.
        J. Comput. Chem. 2022; 43: 431-434
        • Salomon-Ferrer R.
        • Götz A.W.
        • Walker R.C.
        • et al.
        Routine microsecond molecular dynamics simulations with AMBER on GPUs. 2. Explicit solvent particle mesh ewald.
        J. Chem. Theory Comput. 2013; 9: 3878-3888
        • Ryckaert J.P.
        • Ciccotti G.
        • Berendsen H.J.
        Numerical integration of the cartesian equations of motion of a system with constraints: molecular dynamics of n-alkanes.
        J. Comput. Phys. 1977; 23: 327-341
        • Miyamoto S.
        • Kollman P.A.
        Settle: an analytical version of the SHAKE and RATTLE algorithm for rigid water models.
        J. Comput. Chem. 1992; 13: 952-962
        • Gruner S.M.
        Intrinsic curvature hypothesis for biomembrane lipid composition: a role for nonbilayer lipids.
        Proc. Natl. Acad. Sci. USA. 1985; 82: 3665-3669
        • Hamai C.
        • Yang T.
        • Musser S.M.
        • et al.
        Effect of average phospholipid curvature on supported bilayer formation on glass by vesicle fusion.
        Biophys. J. 2006; 90: 1241-1248
        • Sodt A.J.
        • Pastor R.W.
        Molecular modeling of lipid membrane curvature induction by a peptide: more than simply shape.
        Biophys. J. 2014; 106: 1958-1969
        • Mitchell K.T.
        • Ferrell J.E.
        • Huestis W.H.
        Separation of phosphoinositides and other phospholipids by two-dimensional thin-layer chromatography.
        Anal. Biochem. 1986; 158: 447-453
        • Wen Y.
        • Vogt V.M.
        • Feigenson G.W.
        Multivalent cation-bridged PI(4, 5)P2 clusters form at very low concentrations.
        Biophys. J. 2018; 114: 2630-2639
        • Szleifer I.
        • Kramer D.
        • Safran S.A.
        • et al.
        Molecular theory of curvature elasticity in surfactant films.
        J. Chem. Phys. 1990; 92: 6800-6817
        • Frolov V.A.
        • Shnyrova A.V.
        • Zimmerberg J.
        Lipid polymorphisms and membrane shape.
        Cold Spring Harb. Perspect. Biol. 2011; 3: a004747
        • Sodt A.J.
        • Pastor R.W.
        Bending free energy from simulation: correspondence of planar and inverse hexagonal lipid phases.
        Biophys. J. 2013; 104: 2202-2211
        • Baumgart T.
        • Das S.
        • Jenkins J.T.
        • et al.
        Membrane elasticity in giant vesicles with fluid phase coexistence.
        Biophys. J. 2005; 89: 1067-1080
        • Venable R.M.
        • Zhang Y.
        • Pastor R.W.
        • et al.
        Molecular dynamics simulations of a lipid bilayer and of hexadecane: an investigation of membrane fluidity.
        Science. 1993; 262: 223-226
        • Chakraborty S.
        • Doktorova M.
        • Ashkar R.
        • et al.
        How cholesterol stiffens unsaturated lipid membranes.
        Proc. Natl. Acad. Sci. USA. 2020; 117: 21896-21905
        • Nagle J.F.
        • Evans E.A.
        • Dimova R.
        • et al.
        A needless but interesting controversy.
        Proc. Natl. Acad. Sci. USA. 2021;
        • Ashkar R.
        • Doktorova M.
        • Brown M.F.
        • et al.
        Reply to Nagle et al.: the universal stiffening effects of cholesterol on lipid membranes.
        Proc. Natl. Acad. Sci. USA. 2021;
        • Brochard F.
        • Lennon J.
        Frequency spectrum of the flicker phenomenon in erythrocytes.
        J. Phys. France. 1975; 36: 1035-1047
        • Seifert U.
        • Langer S.A.
        Viscous modes of fluid bilayer membranes.
        Europhys. Lett. 1993; 23: 71-76
        • Nagao M.
        • Kelley E.G.
        • Butler P.D.
        • et al.
        Relationship between viscosity and acyl tail dynamics in lipid bilayers.
        Phys. Rev. Lett. 2021; 127: 078102
        • Yamaguchi T.
        • Faraone A.
        Viscoelastic relaxations of high alcohols and alkanes: effects of heterogeneous structure and translation-orientation coupling.
        J. Chem. Phys. 2017; 146: 244506
        • Van Den Bogaart G.
        • Meyenberg K.
        • Jahn R.
        • et al.
        Membrane protein sequestering by ionic protein-lipid interactions.
        Nature. 2011; 479: 552-555
        • Dickson E.J.
        • Hille B.
        Understanding phosphoinositides: rare, dynamic, and essential membrane phospholipids.
        Biochem. J. 2019; 476: 1-23
        • Krajnik A.
        • Brazzo J.A.
        • Bae Y.
        • et al.
        Phosphoinositide signaling and mechanotransduction in cardiovascular biology and disease.
        Front. Cell Dev. Biol. 2020; 8: 595849
        • Toner M.
        • Vaio G.
        • McLaughlin S.
        • et al.
        Adsorption of cations to phosphatidylinositol 4, 5-bisphosphate.
        Biochemistry. 1988; 27: 7435-7443
        • Levental I.
        • Byfield F.J.
        • Janmey P.A.
        • et al.
        Cholesterol-dependent phase separation in cell-derived giant plasma-membrane vesicles.
        Biochem. J. 2009; 424: 163-167
        • Han K.
        • Gericke A.
        • Pastor R.W.
        Characterization of specific ion effects on PI(4, 5)P2 clustering: molecular dynamics simulations and graph-theoretic analysis.
        J. Phys. Chem. B. 2020; 124: 1183-1196
        • Allolio C.
        • Harries D.
        Calcium ions promote membrane fusion by forming negative-curvature inducing clusters on specific anionic lipids.
        ACS Nano. 2021; 15: 12880-12887
        • Hossein A.
        • Deserno M.
        Spontaneous curvature, differential stress, and bending modulus of asymmetric lipid membranes.
        Biophys. J. 2020; 118: 624-642