Lipid bilayer phase behavior
About: Lipid bilayer phase behavior is a(n) research topic. Over the lifetime, 4381 publication(s) have been published within this topic receiving 221959 citation(s).
01 Dec 1973-Zeitschrift für Naturforschung C
TL;DR: A theory of the elasticity of lipid bilayers is proposed and it is argued that in the case of vesicles (= closed bilayer films) the only elasticity controlling nonspherical shapes is that of curvature.
01 May 1997-Biophysical Journal
TL;DR: Molecular dynamics simulations were performed on a system consisting of a bilayer of 64 molecules of the lipid dipalmitoylphosphatidylcholine and 23 water molecules per lipid to reproduce the correct density and to give a proper estimate of the area per lipid.
Abstract: Molecular dynamics simulations of 500 ps were performed on a system consisting of a bilayer of 64 molecules of the lipid dipalmitoylphosphatidylcholine and 23 water molecules per lipid at an isotropic pressure of 1 atm and 50 degrees C. Special attention was devoted to reproduce the correct density of the lipid, because this quantity is known experimentally with a precision better than 1%. For this purpose, the Lennard-Jones parameters of the hydrocarbon chains were adjusted by simulating a system consisting of 128 pentadecane molecules and varying the Lennard-Jones parameters until the experimental density and heat of vaporization were obtained. With these parameters the lipid density resulted in perfect agreement with the experimental density. The orientational order parameter of the hydrocarbon chains agreed perfectly well with the experimental values, which, because of its correlation with the area per lipid, makes it possible to give a proper estimate of the area per lipid of 0.61 +/- 0.01 nm2.
01 Mar 2001-Biophysical Journal
TL;DR: The notion that in biomembranes selected lipids could laterally aggregate to form more ordered, detergent-resistant lipid rafts into which glycosphingolipid- and cholesterol-rich lipid domains partition is strongly supported by this study.
Abstract: One key tenet of the raft hypothesis is that the formation of glycosphingolipid- and cholesterol-rich lipid domains can be driven solely by characteristic lipid-lipid interactions, suggesting that rafts ought to form in model membranes composed of appropriate lipids. In fact, domains with raft-like properties were found to coexist with fluid lipid regions in both planar supported lipid layers and in giant unilamellar vesicles (GUVs) formed from 1) equimolar mixtures of phospholipid-cholesterol-sphingomyelin or 2) natural lipids extracted from brush border membranes that are rich in sphingomyelin and cholesterol. Employing headgroup-labeled fluorescent phospholipid analogs in planar supported lipid layers, domains typically several microns in diameter were observed by fluorescence microscopy at room temperature (24 degrees C) whereas non-raft mixtures (PC-cholesterol) appeared homogeneous. Both raft and non-raft domains were fluid-like, although diffusion was slower in raft domains, and the probe could exchange between the two phases. Consistent with the raft hypothesis, GM1, a glycosphingolipid (GSL), was highly enriched in the more ordered domains and resistant to detergent extraction, which disrupted the GSL-depleted phase. To exclude the possibility that the domain structure was an artifact caused by the lipid layer support, GUVs were formed from the synthetic and natural lipid mixtures, in which the probe, LAURDAN, was incorporated. The emission spectrum of LAURDAN was examined by two-photon fluorescence microscopy, which allowed identification of regions with high or low order of lipid acyl chain alignment. In GUVs formed from the raft lipid mixture or from brush border membrane lipids an array of more ordered and less ordered domains that were in register in both monolayers could reversibly be formed and disrupted upon cooling and heating. Overall, the notion that in biomembranes selected lipids could laterally aggregate to form more ordered, detergent-resistant lipid rafts into which glycosphingolipids partition is strongly supported by this study.
TL;DR: It is proposed that membranes whose proteins and polar lipids are distributed asymmetrically in the two halves of the membrane bilayer can act as bilayer couples, i.e., theTwo halves can respond differently to a perturbation.
Abstract: We propose that membranes whose proteins and polar lipids are distributed asymmetrically in the two halves of the membrane bilayer can act as bilayer couples, i.e., the two halves can respond differently to a perturbation. This hypothesis is applied to the interactions of amphipathic drugs with human erythrocytes. It is proposed that anionic drugs intercalate mainly into the lipid in the exterior half of the bilayer, expand that layer relative to the cytoplasmic half, and thereby induce the cell to crenate, while permeable cationic drugs do the opposite and cause the cell to form cup-shapes. This differential distribution of the drugs is attributed to interactions with the phosphatidylserine that is concentrated in the cytoplasmic half of the membrane. Impermeable amphipathic drugs intercalate only into the exterior half of the bilayer, and therefore are crenators of the intact cell. Several predictions of this hypothesis have been confirmed experimentally with erythrocytes and erythrocyte ghosts. The bilayer couple hypothesis may contribute to the explanation of many membrane-mediated phenomena in cell biology.
01 Nov 2003-Biophysical Journal
Abstract: We use fluorescence microscopy to directly observe liquid phases in giant unilamellar vesicles. We find that a long list of ternary mixtures of high melting temperature (saturated) lipids, low melting temperature (usually unsaturated) lipids, and cholesterol produce liquid domains. For one model mixture in particular, DPPC/DOPC/Chol, we have mapped phase boundaries for the full ternary system. For this mixture we observe two coexisting liquid phases over a wide range of lipid composition and temperature, with one phase rich in the unsaturated lipid and the other rich in the saturated lipid and cholesterol. We find a simple relationship between chain melting temperature and miscibility transition temperature that holds for both phosphatidylcholine and sphingomyelin lipids. We experimentally cross miscibility boundaries both by changing temperature and by the depletion of cholesterol with β-cyclodextrin. Liquid domains in vesicles exhibit interesting behavior: they collide and coalesce, can finger into stripes, and can bulge out of the vesicle. To date, we have not observed macroscopic separation of liquid phases in only binary lipid mixtures.