1996 年 21 巻 5 号 p. 311-317
It was now well established that phosphatidylcholines or phosphatidylglycerols can form an interdigitated structural phase (Iphase), in which acyl chains of the lipids fully interpenetrate the hydrocarbon chains of the opposing monolayer in the presence of short chain alcohols and some other amphiphiles. It has been suggested that the interdigitated structure as well as a hexagonal II structure plays an important role in regulating many functions of biological membranes. We have demonstrated the participation ofIphase formation in ethanol-induced liposomal aggregation and fusion. We have also focused on control of permeability as one of the biomembrane functions, and the effects of ethanol on the permeability of large unilamellar vesicles composed of various phospho-lipids were studied by monitoring the leakage of the fluorescent dye, calcein, entrapped in the inner aqueous phase of the vesicles. In the cases of mixed membranes composed of DPPC and dilauroyl phosphatidylethanolamine (DLPE), as well as DPPC liposomal membranes, large permeabilities were observed in the wide range of ethanol concentrations, where the normal bilayer andIphase coexist and the membrane is in a phase-separated state. These results suggested that ethanol can disturb the normal control of biological membrane permeability.