Trapping of short-lived intermediates in phospholipid phase transitions: The Lα* phase

Abstract

Time-resolved small-angle X-ray diffraction of liquid-crystalline phospholipid–water systems under temperature or pressure jump conditions has demonstrated the existence of an ordered, intermediate L_α phase, with a sub-second lifetime, designated as the L_α^*-phase. The lamellar repeat spacing is, universally, 0.3 nm smaller than that of the parent phase, irrespective of the lipid composition and of the jump conditions, provided that the jump leads to a net volume expansion of the phase. The presence of salts, most notably LiCl, leads to a prolongation of the lifetime. The results suggest a non-monotonic potential function for the interbilayer water thickness.