Pressure Induced Topological Phase Transitions in Membranes

TL;DR

This study investigates how high pressure induces phase transitions in lipid-water liquid crystals, revealing changes in structure, transition volume, and the formation of an intermediate cubic phase, supported by experimental data.

Contribution

It provides experimental evidence of pressure-induced topological phase transitions and the formation of an intermediate cubic phase in lipid-water systems.

Findings

Unit cell size of $H_{II}$ phase increases with pressure

Transition volume $V_{bh}$ decreases and vanishes at high pressure

Increase in scattered light intensity linked to intermediate cubic phase formation

Abstract

Some highly unusual features of a lipid-water liquid crystal are revealed by high pressure x-ray diffraction, light scattering and dilatometric studies of the lamellar (bilayer $L_{\alpha}$) to nonlamellar inverse hexagonal ($H_{II}$) phase transition. (i) The size of the unit cell of the $H_{II}$ phase increases with increasing pressure. (ii) The transition volume, $\Delta V_{bh}$, decreases and appears to vanish as the pressure is increased. (iii) The intensity of scattered light increases as $\Delta V_{bh}$ decreases. Data are presented which suggest that this increase is due to the formation of an intermediate cubic phase, as predicted by recent theoretical suggestions of the underlying universal phase sequence.