Self-association patterns of sodium taurocholate and taurodeoxycholate as studied by frontal derivative chromatography

The aggregation patterns of sodium taurocholate (TC) and taurodeoxycholate (TDC) in an isotonic sodium chloride solution at 298.2 K are investigated b y frontal derivative chromatography on Sephadex G-10 columns and are quanti tatively analyzed on the basis of several aggregation models. The aggregati on parameters are best fitted to the observed centroid volume data. The der ivative chromatogram of TC at 6.006 mM simulated on the basis of a stepwise aggregation model is in excellent agreement with the observed one, whereas the simulation on the basis of the pentamerization model remarkably differ s in shape from the observed one. The derivative chromatograms of TDC at 1. 500 and 2.003 mM simulated on the basis of another stepwise aggregation mod el are closer to the observed ones than those of the Bottari-Festa model. T hus, TC and TDC form their dimers and polydisperse micelles. These conclusi ons are supported by the fitness to the centroid volume data. In light of t he present results and current reports, the structure and counterion bindin g of bile salt micelles are discussed.