Structural intermediates in phase transitions involving crystalline phase bilayers of monogalactosyldiacylglycerol in water

Abstract

The mechanism of transition of a saturated monogalactosyldiacylglycerol-water system from low-temperature crystal phases (L C1 and L C2) to the liquid-crystal phase (α) has been examined by time-resolved X-ray diffraction methods. The transition between the metastable L C1 phase and the liquid-crystalline phase involves a continuous transition from one phase to the other with apparently no intermediate phases with lifetimes greater than 100 ms. The transition between the L C2 phase and the liquid-crystalline phase, by contrast, is complex and involves intermediate phases or transitory states with lifetimes of a few hundred milliseconds. This complex behavior appears to be related to the existence of multiple-phase pathways along which the L C2 phase may proceed to the liquid-crystalline phase and there is evidence that both metastable L C1 phase and a lamellar gel phase (L β) may be involved.