Hydrophobic Self-Association of Sodium Taurochenodeoxycholate and Tauroursodeoxycholate

Abstract

The aggregation patterns of sodium taurochenodeoxycholate (TCDC) and tauroursodeoxycholate (TUDC) in an isotonic sodium chloride solution are investigated by frontal chromatography on Sephadex G-10 columns at 298.2 K and are quantitatively analyzed on the basis of stepwise aggregation models. The micellar aggregation numbers, critical micelle concentrations (cmc's), stepwise aggregation constants, and micelle size distributions of TCDC and TUDC are determined and compared to those of sodium taurocholate and taurodeoxycholate. The logarithms of gel−water partition coefficients, dimerization constants, and reciprocal cmc values for the four bile salts exhibit linearity with their hydrophobic molecular surface areas, and the slopes are close to that of the logarithms of reciprocal cmc values against the hydrophobic molecular surface areas of lecithins. This fact shows that the gel adsorption, dimerization, and micellization of bile salts are driven mainly by hydrophobic interactions and that the Small model ...