BEHAVIORS OF SODIUM TAUROCHOLATE AND SODIUM TAURODEOXYCHOLATE IN BINARY MIXED MICELLES OF BILE-SALT AND NONIONIC SURFACTANT

Behavior of sodium taurocholate (NaTC) and sodium deoxycholate (NaTDC) in binary mixed micelles consisting of bile salt and octaethylene gly col mono-n-decyl ether (C(10)E(8)) has been studied on the basis of mi cellar compositions, polarities of interior of intramicelles, mean agg regation numbers, and H-1-NMR. measurements, respectively. Micellar co mpositions for both the NaTC-C(10)E(8) system and NaTDC-C(10)E(8) syst em tended to change from C(10)E(8)-rich micelles to bile-salt-rich mic elles with the mole fraction of bile salts from the results of both th eoretical calculations using critical micellar concentration (cmc) and the micellar polarity, and also a microenvironment of intramicelles f or the NaTDC-C(10)E(8) system was more hydrophobic than that for the N aTC-C(10)E(8) system. Mean aggregation numbers of mined micelles for b oth systems abruptly decreased with the increase of mole fraction of b ile salts in the range of the low mole Fraction, but mean aggregation numbers for the NaTDC-C(10)E(8) system were larger than those for NaTC -C(10)E(8) system. Furthermore, from the results of H-1-NMR measuremen ts, the methyl group protons at the 18, 19, and 21 positions in NaTC m olecules were found to have a slight freedom with an increase of mole fraction of NaTC, but; those of NaTDC were found to be restricted with an increase of mole fraction of NaTDC.