Sterols sense swelling in lipid bilayers

Abstract

In the mimetic membrane system of phosphatidylcholine bilayers, thickening ("pre-critical behavior", "anomalous swelling") of the bilayers is observed, in the vicinity of the main transition, which is nonlinear with temperature. The sterols cholesterol and androsten are used as sensors in a time-resolved simultaneous small-and wide angle x-ray diffraction study to investigate the cause of the thickening. We observe precritical behavior in the pure lipid system, as well as with sterol concentrations less than 15%. To describe the precritical behavior we introduce a theory of precritical phenomena. The good temperature resolution of the data shows that a theory of the influence of fluctuations needs modification. The main cause of the critical behavior appears to be a changing hydration of the bilayer.

Chain length dependence of anomalous swelling in multilamellar lipid vesicles

“…The anomaly consists in a continuous increase in repeat distance with decreasing temperature towards the main transition temperature T m . Anomalous swelling behaviour of DMPC in the liquid crystalline phase has also been reported in [3][4][5].…”

Lipid bilayer structure

“…The temperature dependence of D in DMPC and DPPC accelerates as the temperature is lowered towards the main transition [30][31][32][33]. It appears that half this increase is due to thickening of the bilayer caused by a pretransitional straightening of the hydrocarbon chains as T is reduced [32][33][34].…”

The effects of cholesterol and β-sitosterol on the structure of saturated diacylphosphatidylcholine bilayers

“…Both the pretransition and the main phase transition are suppressed. As a result of the greater ordering of lipid chains at temperatures corresponding to the fluid phase of the neat phospholipid, the thickness of the phosphatidylcholine bilayer increases (McIntosh 1978;Pencer et al 2005;Richter et al 1999).…”