Studies on the microstructure of bile salt aggregates in aqueous n-alkanol solutions by Small Angle Neutron Scattering

Small Angle Neutron Scattering (SANS) measurements on two bile salt micelle systems sodium cholate (NaC) and sodium deoxycholate (NaDC) each 0.1 M in the absence and presence of 0.05 M 1-butanol, 1-pentanol, 1-hexanol and 1-octanol were carried out in D20 at ambient conditions (25 degrees C). The scattering cross-section as a function of wave vector transfer (Q) showed the presence of correlation peaks characteristic of strong inter micellar interactions. The correlation peak positions were shifted to low Q values in the presence of n-alkanols for both NaC and NaDC micelles. Best fit curves of SANS were produced by applying Hayter-Penfold analysis considering monodisperse ellipsoid model for the micelles. The best fits were found for constant semi-minor axis = 8A with an increasing semi-major axis for increasing n-alkanol chain lengths. The micellar growths in presence of n-alkanols were studied using the ESR correlation time measurements on suitable spin probe incorporated micelles. The growth parameter and the hydrodynamic radii values were found to be agreeable with SANS data. Intermicellar interaction potentials seem to increase with the Cn of n-alkanols.