Smoothed acyl chain orientational order parameter profiles in dimyristoylphosphatidylcholine-distearoylphosphatidylcholine mixtures: a 2H-NMR study

Lu, Dalian; Vavasour, I.; Morrow, Michael R.

doi:10.1016/s0006-3495(95)80219-5

Cited by 39 publications

(40 citation statements)

References 37 publications

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“…From phosphorus site distributions and order parameters, it is apparent that the headgroups of the two lipid types are conformationally nearly indistinguishable, particularly at 22.5 and 48.7% DLPC. Taking together the observations of density profiles and order parameters, the structure of these mixtures appears to be quite consistent with the picture of DMPC/DSPC fluid mixtures described by Lu et al 13 on the basis of NMR measurements of smoothed C-D bond order parameters. The DPPC tails extend to fill in a disordered zone around the bilayer midplane in which they have significant overlap with the opposing leaflet.…”

Section: Discussionsupporting

confidence: 87%

Equilibrium Distributions of Dipalmitoyl Phosphatidylcholine and Dilauroyl Phosphatidylcholine in a Mixed Lipid Bilayer: Atomistic Semigrand Canonical Ensemble Simulations

et al. 2006

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Conventional molecular dynamics (MD) simulations are seriously limited by the slow rate of diffusive mixing in their ability to predict lateral distributions of different lipid types within mixed-lipid bilayers using atomistic models. A method to overcome this limitation, using configuration-bias Monte Carlo (MC) "mutation" moves to transform lipids from one type to another in dynamic equilibrium, is demonstrated in binary fluid-phase mixtures of lipids whose tails differ in length by four carbons. The hybrid MC-MD method operates within a semigrand canonical ensemble, so that an equilibrium composition of the mixture is determined by a constant difference in chemical potential (Delta(mu)) chosen for the components. Within several nanoseconds, bilayer structures initiated as pure dipalmitoyl phosphatidylcholine (DPPC) or pure dilauroyl phosphatidylcholine (DLPC) converge to a common composition and structure in independent simulations conducted at the same Delta(mu). Trends in bilayer thickness, area per lipid, density distributions across the bilayer, and order parameters have been investigated at three mixture compositions and compared with results from the pure bilayers at 323 K. The mixtures showed a moderate increase in DPPC acyl tail sites crossing the bilayer midplane relative to pure DPPC. Correlations between lateral positions of the two lipid types within or across the bilayer were found to be weak or absent. While the lateral distribution is consistent with nearly ideal mixing, the dependence of composition on Delta(mu) indicates a positive excess free energy of mixing.

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Section: Discussionsupporting

confidence: 87%

Equilibrium Distributions of Dipalmitoyl Phosphatidylcholine and Dilauroyl Phosphatidylcholine in a Mixed Lipid Bilayer: Atomistic Semigrand Canonical Ensemble Simulations

et al. 2006

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“…This agrees well with high acyl chain dynamics found in NMR studies of bilayers with significant chainlength mismatch: Although the methylene groups of the longer acyl chains penetrate, on average, across the bilayer midplane, they are highly disordered and their mobility is not significantly constrained by interaction with the opposite leaflet [32]. Our result is also in line with a number of experimental and modeling studies that have shown a high propensity for acyl chain backfolding, i.e., a significant probability of finding the methyl group of a given chain close to the headgroup region of the same leaflet [33].…”

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confidence: 88%

Long and Short Lipid Molecules Experience the Same Interleaflet Drag in Lipid Bilayers

2013

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Membrane interleaflet viscosity η e affects tether formation, phase separation into domains, cell shape changes, and budding. Contrary to the expected contribution to interleaflet coupling from interdigitation, the slide of lipid patches in opposing monolayers conferred the same value η e ≈ 3×10 9 J s m −4 for the friction experienced by the ends of both short and long chain fluorescent lipid analogues. Consistent with the weak dependence of the translational diffusion coefficient on lipid length, the in-layer viscosity was, albeit length dependent, much smaller than η e .The ability of the two membrane leaflets to slide against each other is of utmost importance for manifold cellular processes like (i) filopodia formation in cell migration [1], (ii) tether formation for neutrophil attachment to platelets during inflammation or thrombosis [2], (iii) membrane fusion [3], or (iv) membrane budding and fission [4]. In order for signaling platforms, so-called rafts to emerge, sterol and sphingolipid enriched domains must align in the two membrane monolayers [5]. Experiments on lipid bilayers suggest that such alignment is stabilized by a yet unidentified coupling mechanism. For example, lipid mixture in one leaflet of asymmetric lipid bilayers may induce the formation of registered clusters on the other leaflet, though it contains lipids which would not phase separate in a symmetric bilayer [6]. Finally, lipid interactions at the membrane midplane seem to have an impact on the mobility of individual lipid molecules [7].What actually determines how tightly the leaflets are coupled to each other or how easily they slide against each other is under debate [6,[8][9][10]. For example, minimization of energy expenses on local curvature [11] or maximization of the free undulation energy [12] have been put forward to explain registration of ligand-induced lipid spots of higher chain orientational order in the two leaflets. Gelation of both leaflets upon binding of negatively charged particles to only one monolayer of initially homogenous fluid lipid bilayers [13] may reflect a decreased capacity of one leaflet to accommodate disorder due to bindinginduced local stiffening of the other leaflet.

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“…Because phosphatidylcholines are most abundant in biological membranes, DMPC/DSPC is the most thoroughly investigated two-component lipid bilayer (Koynova and Caffrey, 1998). The thermodynamic parameters of DMPC/ DSPC bilayers have been examined experimentally by a number of experimental methods including differential scanning calorimetry (DSC) (Mabrey and Sturtevant, 1976;Van Dijck et al, 1977;Koynova and Caffrey, 1998), dilatometry (Wilkinson and Nagle, 1979), densitometry (Schmidt and Knoll, 1986), neutron scattering (Knoll et al, 1981(Knoll et al, , 1983, nuclear magnetic resonance (NMR) (Lu et al, 1995;, ESR , Raman spectorscopy (Mendelsohn and Maisano, 1978), and Fourier transformed infrared spectroscopy (Brumm et al, 1996). The structural characteristics of the fluid and gel coexistence region have been examined experimentally by using fluorescance recovery after photobleaching (FRAP) (Vaz et al, 1989;Schram et al, 1996), fluorescence spectroscopy (Piknova et al, 1996), and electron spin resonance (ESR) .…”

Section: Introductionmentioning

confidence: 99%

Component and State Separation in DMPC/DSPC Lipid Bilayers:A Monte Carlo Simulation Study

Michonova-Alexova

Sugár

2002

Biophysical Journal

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In this paper a two-state, two-component, Ising-type model is used to simulate the lateral distribution of the components and gel/fluid state acyl chains in dimyristoylphosphatidylcholine/distearoylphosphatidylcholine (DMPC/DSPC) lipid bilayers. The same model has been successful in calculating the excess heat capacity curves, the fluorescence recovery after photobleaching (FRAP) threshold temperatures, the most frequent center-to-center distances between DSPC clusters, and the fractal dimensions of gel clusters (Sugar, I. P., T. E. Thompson, and R. L. Biltonen, 1999. Biophys. J. 76:2099-2110). Depending on the temperature and mole fraction the population of the cluster size is either homogeneous or inhomogeneous. In the inhomogeneous population the size of the largest cluster scales with the size of the system, while the rest of the clusters remain small with increasing system size. In a homogeneous population, however, every cluster remains small with increasing system size. For both compositional and fluid/gel state clusters, threshold temperatures-the so-called percolation threshold temperatures-are determined where change in the type of the population takes place. At a given mole fraction, the number of percolation threshold temperatures can be 0, 1, 2, or 3. By plotting these percolation threshold temperatures on the temperature/mole fraction plane, the diagrams of component and state separation of DMPC/DSPC bilayers are constructed. In agreement with the small-angle neutron scattering measurements, the component separation diagram shows nonrandom lateral distribution of the components not only in the gel-fluid mixed phase region, but also in the pure gel and pure fluid regions. A combined diagram of component and state separation is constructed to characterize the lateral distribution of lipid components and gel/fluid state acyl chains in DMPC/DSPC mixtures. While theoretical phase diagrams of two component mixtures can be constructed only in the case of first-order transitions, state and component separation diagrams can be constructed whether or not the system is involved in first-order transition. The effects of interchain interactions on the component and state separation diagrams are demonstrated on three different models. The influences of state and component separation on the in-plane and off-plane membrane reactions are discussed.

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Smoothed acyl chain orientational order parameter profiles in dimyristoylphosphatidylcholine-distearoylphosphatidylcholine mixtures: a 2H-NMR study

Cited by 39 publications

References 37 publications

Equilibrium Distributions of Dipalmitoyl Phosphatidylcholine and Dilauroyl Phosphatidylcholine in a Mixed Lipid Bilayer: Atomistic Semigrand Canonical Ensemble Simulations

Equilibrium Distributions of Dipalmitoyl Phosphatidylcholine and Dilauroyl Phosphatidylcholine in a Mixed Lipid Bilayer: Atomistic Semigrand Canonical Ensemble Simulations

Long and Short Lipid Molecules Experience the Same Interleaflet Drag in Lipid Bilayers

Component and State Separation in DMPC/DSPC Lipid Bilayers:A Monte Carlo Simulation Study

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