Structures and phase transitions in aqueous dispersions of branched-chain glycerophosphoethanolamines

Glycerophosphoethanolamines with alpha-branched fatty acids were synthesize d, varying the side-chain length. Differential scanning calorimetry and X-r ay diffraction were applied to investigate the influence of the chemical al teration on the physico-chemical parameters and the structures formed in li pid-water dispersions. The results show that the introduction and stepwise elongation of side-chains decrease the transition temperature from gel to l iquid-crystalline phases. The T-m values pass through a minimum and increas e slightly on going to the triple-chain lipid. The change in the transition parameters is connected with a modified polymorphism. Short side-chains in duce a tilt in the gel state and the elongation of the branch leads to inte rdigitated gel phases. With increasing side-chain length, non-lamellar liqu id-crystalline phases are stabilized. For the long-branched derivative, an interdigitation of head-groups from adjacent bilayers is proposed.