Choline and acetylcholine induce interdigitation of hydrocarbon chains in dipalmitoylphosphatidylglycerol lamellar phase with stiff chains

摘要: In some soap gels [l] and in L-DPPG-water system [2] lamellar phases have been observed which the hydrocarbon chains, stiff parallel to each other, interdigitate; other words, CH3 ends of chains one layer are near polar groups opposite (see fig. 1C). From operational standpoint these characterized by: (i) The thickness lipid bilayer, is almost one-half value expected for non-interdigitating phase L/3; (ii) area per group at lipid-water interface, 4-times cross-section chain; (iii) intensities reflections. Moreover, 3 types organization observed; by a family sharp reflections 0.240-0.780 A ’ range, correspond two-dimensional lattices: p6, cmm pgg. detailed description can be found PI. NH4 became available us [5,6] we searched interdigitated but failed observe it. This negative result prompted study batches L-DPPG-NH4, also from Serdary; again phase. Similarly, Watts et al. [3,4] who studied as function pH, did not report discrepancy between our early observations those all subsequent studies was puzzling. An explanation could sought presence impurity sample used work: since preparation that involved DPPG-glycerol transesterification step, likely candidate choline. We demonstrate here indeed choline, well acetylcholine promote interdigitation; show [13] antibiotic polymyxin B has same effect.