Rupert L A, van Breemen J F, van Bruggen E F, Engberts J B, Hoekstra D
J Membr Biol. 1987;95(3):255-63. doi: 10.1007/BF01869487.
Electron microscopic techniques have been employed to investigate the ability of didodecylphosphate vesicles (diameter approx. 900 A) to fuse in the presence of Ca2+. As revealed by negative staining, Ca2+ induces extensive fusion and large vesicles with diameters up to 7000 A are formed. In a process secondary to fusion, the fused vesicles display a tendency to flatten and are subsequently transformed into extended tubular structures. Freeze-fracture electron microscopy, in conjunction with 31P NMR and selected area electron diffraction measurements indicate that the tubes are packed in a hexagonal (HII) array and that the amphiphiles are converted from the lamellar to the hexagonal HII phase. The relationship between membrane fusion and the lamellar-to-hexagonal phase transition is discussed in terms of formation and abundance of transiently stable inverted micellar intermediates at contact regions between two interacting membranes. A model for the conversion of the (vesicular) lamellar into the (tubular) hexagonal HII phase is presented, taking into account the molecular shape of the amphiphile. The relevance of using simple synthetic amphiphiles as models for phospholipid bilayers and complex biomembrane behavior is briefly discussed.
已采用电子显微镜技术研究了二月桂基磷酸酯囊泡（直径约900埃）在Ca2+存在下的融合能力。如负染色所示，Ca2+诱导广泛融合并形成直径达7000埃的大囊泡。在融合的继发过程中，融合的囊泡呈现出扁平化的趋势，随后转变为延伸的管状结构。冷冻断裂电子显微镜结合31P核磁共振和选区电子衍射测量表明，这些管子以六方（HII）阵列排列，两亲分子从层状相转变为六方HII相。根据两个相互作用膜接触区域中瞬态稳定的反胶束中间体的形成和丰度，讨论了膜融合与层状-六方相转变之间的关系。考虑到两亲分子的分子形状，提出了一个从（囊泡状）层状相转变为（管状）六方HII相的模型。简要讨论了使用简单合成两亲分子作为磷脂双层模型和复杂生物膜行为的相关性。
