Small-angle neutron scattering study of sodium cholate and sodium deoxycholate interacting micelles in aqueous medium

Small angle neutron scattering (SANS) measurements of D2O solutions (0,10 M) of sodium cholate (NaC) and sodium deoxycholate (NaDC) were carried out at T = 298 K. Under compositions very much above the critical micelle concentration (CMC), the bile salt micelle size growths were monitored by adopting Hayter–Penfold type analysis of the scattering data. NaC and NaDC solutions show presence of correlation peaks at Q = 0,12 and 0,10 Å–1 respectively. Monodisperse ellipsoids of the micelles produce best fits. For NaC and NaDC systems, aggregation number (9,0, 16,0), fraction of the free counterions per micelle (0,79, 0,62), semi-minor (8,0 Å) and semi-major axes (18,4, 31,7 Å) values for the micelles were deduced. Extent of micellar growth was studied using ESR correlation time measurements on a suitable probe incorporating NaC and NaDC micelles. The growth parameter (axial ratio) values were found to be 2,3 and 4,0 for NaC and NaDC systems respectively. The values agree with those of SANS.