EXAFS: a new approach to the structure of micellar aggregates

Abstract

A helical model was previously proposed for sodium (NaDC) and rubidium (RbDC) deoxycholate micellar aggregates in\naqueous solutions. SAXS, NMR, ESR, and CD meehurements verified the helical model. Here we report an EXAFS study\nby the spherical wave formalism on the coordination of the Rb' ions in the crystal, macromolecular fiber, and micellar aqueous\nsolution of RbDC together with measurements carried out on rubidium oxalate (crystal and aqueous solution). The results\nshow that the Rb" ions of the micellar aggregates have the same (or very similar) peculiar coordination as that inside the\nhelices of the crystal and macromolecular fiber. Moreover, their coordination remarkably differs from that observed in the\naqueous solutions of rubidium oxalate, where the situation would be similar to that of a classical micelle. Thus, the helical\nmodel is unquestionably confirmed.