Intermolecular interactions in sodium deoxycholate micelles: an NMR study involving a spin-labeled cholestane

Abstract

A IH and I3C NMR study of the interaction between sodium deoxycholate (NaDC) micelles and a nitroxide probe (cholestane spin-label, CSL) is presented. It is shown that CSL primarily interacts with the fi face of NaDC. The 'H NMR relaxation data enable the spatial geometry of the interaction to be defined. van der Waals energy calculations show that the CSL-NaDC interaction corresponds to a minimum if a helical model, previously proposed, is assumed for the NaDC micelle. At high concentrations of CSL, the CSL-NaDC interaction changes and the a face of NaDC may also become involved in the interaction.