Sugioka H, Moroi Y
Department of Chemistry, Faculty of Science, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan.
Biochim Biophys Acta. 1998 Oct 2;1394(1):99-110. doi: 10.1016/s0005-2760(98)00090-3.
The micellization of sodium cholate (NaC) was studied at 298.2 K by aqueous solubility at different pH values. Using a stepwise association model of cholate anions without the sodium counterion, the aggregation number (n) of the cholate micelle was evaluated and found to increase with the total concentration, indicating that the mass action model worked quite well. The n value at 60 mM was found equal to 16. The membrane potential measurement of sodium ion with a cation exchange membrane was made in order to confirm the low counterion binding to micelle. The solubilization of alkylbenzenes (benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, n-pentylbenzene, n-hexylbenzene) and polycyclic aromatic compounds (naphthalene, anthracene, pyrene) into the aqueous micellar solution of sodium cholate was carried out. Solubilizate concentrations at equilibrium were determined spectrophotometrically at 298.2 K. The first stepwise association constants (K1) between solubilizate monomer and vacant micelle were evaluated from the equilibrium concentrations and found to increase with increasing hydrophobicity of the solubilizate molecules. From the Gibbs energy change for solubilization at the different mean aggregation numbers and from molecular structure of the solubilizates, the function of sodium cholate micelle for solubilization was discussed and was compared with data from conventional aliphatic micelles.
在298.2 K下，通过不同pH值下的水溶性研究了胆酸钠（NaC）的胶束化作用。使用不考虑钠离子抗衡离子的胆酸根阴离子逐步缔合模型，对胆酸胶束的聚集数（n）进行了评估，发现其随总浓度增加，这表明质量作用模型效果良好。发现60 mM时的n值等于16。为了确认抗衡离子与胶束的低结合，用阳离子交换膜进行了钠离子膜电位测量。进行了烷基苯（苯、甲苯、乙苯、正丙苯、正丁苯、正戊苯、正己苯）和多环芳烃（萘、蒽、芘）在胆酸钠水胶束溶液中的增溶作用研究。在298.2 K下用分光光度法测定了平衡时增溶物的浓度。根据平衡浓度评估了增溶物单体与空胶束之间的第一步缔合常数（K1），发现其随增溶物分子疏水性的增加而增大。根据不同平均聚集数下增溶作用的吉布斯自由能变化以及增溶物的分子结构，讨论了胆酸钠胶束的增溶作用，并与传统脂肪族胶束的数据进行了比较。
