Meyuhas D, Lichtenberg D
Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Ramat-Aviv, Israel.
Biochim Biophys Acta. 1995 Mar 22;1234(2):203-13. doi: 10.1016/0005-2736(94)00290-6.
Dilution of phospholipid-detergent mixed micellar systems results in an increase of the fraction of monomeric detergent and, consequently, in a decrease of the effective ratio Re between non-monomeric detergent and phospholipid. The value of Re has been previously shown to be the main determinant of the state of aggregation in such mixtures: at Re values below a critical value ReSAT, the mixture is vesicular; at Re values higher than ReSOL, the mixture is micellar, whereas within the range of ReSAT-ReSOL, vesicles and micelles co-exist. Albumin binds bile salts. Therefore, in PC-cholate mixtures, Re is reduced by the presence of albumin in the system. Within the range of PC concentrations of 2-23 mM, cholate concentrations of 2-15 mM and BSA concentrations of 0-100 mg/ml, binding of cholate to BSA results in reduction of the effective cholate concentration to the extent of 0.11 mM cholate per 1 mg/ml BSA, namely up to 7 cholate molecules bind to each BSA molecule. Yet, the values of ReSAT and ReSOL are essentially independent of BSA. In addition, at any given Re value, the size of vesicles made by dilution of mixed micelles is a complex function of albumin and PC concentrations. Possible mechanistic details which may cause this effect are discussed. These effects of albumin on the state of aggregation of PC-cholate mixtures must be taken into account in studies of such mixtures in the presence of albumin when other effects of albumin (e.g., on phospholipolysis) are investigated. Practical conclusions are reached with respect to the procedures that can be used to prepare vesicles of identical composition and size in the presence of different concentrations of albumin.
磷脂 - 去污剂混合胶束体系的稀释会导致单体去污剂比例增加，进而使非单体去污剂与磷脂之间的有效比例Re降低。先前已表明，Re值是此类混合物聚集状态的主要决定因素：当Re值低于临界值ReSAT时，混合物呈囊泡状；当Re值高于ReSOL时，混合物呈胶束状，而在ReSAT - ReSOL范围内，囊泡和胶束共存。白蛋白结合胆汁盐。因此，在PC - 胆酸盐混合物中，体系中白蛋白的存在会降低Re值。在PC浓度为2 - 23 mM、胆酸盐浓度为2 - 15 mM以及BSA浓度为0 - 100 mg/ml的范围内，胆酸盐与BSA的结合会使有效胆酸盐浓度降低，即每1 mg/ml BSA降低0.11 mM胆酸盐，也就是说每个BSA分子最多可结合7个胆酸盐分子。然而，ReSAT和ReSOL的值基本上与BSA无关。此外，在任何给定的Re值下，通过混合胶束稀释形成的囊泡大小是白蛋白和PC浓度的复杂函数。文中讨论了可能导致这种效应的机制细节。在研究白蛋白存在下PC - 胆酸盐混合物的其他效应（例如对磷脂分解的影响）时，必须考虑白蛋白对PC - 胆酸盐混合物聚集状态的这些影响。对于在不同浓度白蛋白存在下制备相同组成和大小囊泡的可用程序得出了实际结论。
