STUDIES OF SODIUM TAUROCHOLATE MICELLES USING FLUORESCENT PROBE MOLECULES

Abstract Micelles formed by sodium taurocholate (NaTC) and mixed micelles formed by NaTC with detergents (SDS, reduced Triton X-100 and CTAC) were studied with fluorescent probes. Pyrene was used as an indicator of the polarity of the micellar binding site by comparison of the fluorescence spectra and vibronic band intensity ratios of pyrene in the different systems. Perylene was used as a fluorescence polarization probe to study the rigidity of the NaTC and mixed micelles. The fluorescence lifetime of perylene in the different systems was also measured. Results of the studies were compared with measurements of the probes in cyclohexane, ethanol and aqueous beta-cyclodextrin. Perylene was found to be more rigidly bound in the NaTC micelles than in the detergent micelles. Insertion of small amounts of reduced Triton X-100 into the NaTC micelles appears to increase the rigidity. The binding sites of NaTC and CTAC have similar polarities, and are more polar than those of SDS and reduced Triton X-100. Insertion of any of the detergents into the NaTC micelle decreases the polarity of the binding site, possibly by reducing the penetration of water into the micelle.