A Two-step Aggregation Scheme of Bile Acid Salts, as Seen From Computer Simulations

Abstract

The concentration dependence of the aggregation scheme of two bile anions, i.e., cholate and deoxycholate is investigated in aqueous environment on the basis of molecular dynamics computer simulations. The distribution of the probability that a bile ion belongs to a cluster of a given size is determined. In the analysis we distinguish between hydrogen bonding connections and links of hydrophobic origin. ne results show that at low concentrations the systems contain small primary micelles, built up by no more than 10 ions. For cholate, these primary micelles are either kept together by hydrophobic interactions, or by hydrogen bonds, whereas in the case of deoxycholate the number of the hydrogen bonded aggregates is negligibly small. At high concentrations large secondary micelles are formed by the attachment of primary hydrophobic micelles to each other by hydrogen bonds.