Conductometric and 1H NMR determination of the critical micellar concentrations of two oxo-derivatives of cholic acid. Which of the two is more hydrophobic?
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Conductometric and 1H NMR determination of the critical micellar concentrations of two oxo-derivatives of cholic acid. Which of the two is more hydrophobic?
Zdrojový dokument:Sensing in electroanalysis. K. Vytřas, K. Kalcher, I. Švancara (Eds.). 2010, Volume 5.
Abstrakt:
Critical micellar concentrations (CMCs) were determined for two novel
promoters of membrane permeability – 7-monoketocholic acid (7-MKC) and 12-
monoketocholic acid (12-MKC), using two non-invasive (conductometry and 1H NMR
relaxation experiment) methods. Studies by these methods suggest the different
aggregation abilities of the investigated bile acid derivatives. In an aqueous solution,
7-MKC has a somewhat lower CMC value (43 mM) than 12-MKC (50 mM). Further,
it was found that, in addition to the primary micelles, 7-MKC forms also secondary
micelles. Based on the CMC value 7-MKC is more hydrophobic than 12-MKC,
although the opposite data can be found in the literature. The apparent hydrophobicity
of 7-MKC is a consequence of the formation of secondary micelles, shifting the
monomer equilibrium to the direction of first micelles, which is manifested as a
decrease in the CMC value.