Evidence for a role of phosphatidyl ethanolamine as a modulator of membrane-membrane contact.

摘要: Phosphatidyl ethanolamine (PE) is shown to be effective in producing membrane aggregation. The aggregation of PE and PE/PC (phosphatidyl choline) mixed vesicles was studied as a function pH cation composition the medium. kinetics equilibria were stopped-flow rapid mixing experiments, which prepared at 9.2 “jumped” 7. H+ ions protonate PE− promote vesicle cooperative fashion. Vesicles containing PC have decreased tendency aggregate compared pure vesicles. apparent rate constant for about two orders magnitude below that diffusion controlled virtually same A theoretical description equilibrium developed terms three parameters: protonation (K A ), (K eq) number molecules an area must interact order (N eff). These parameters are with values trends expected electrostatic calculations based on dipolar repulsion short-range binding, hydrogen bonding may contribute. results interpreted self-consistent fashion indicate: (i) mix randomly, (ii) head-to-tail binding occurs between PE(PC) apposing vesicles, (iii) screening accounts decrease inK molar fraction per vesicle, (iv) 90% protonated before can occur, (v) all lipid systems we considered, point extent dimerization half maximal close physiological pH, indicating regulatory effect biological systems.