Composition of sodium taurocholate micellar solutions

Abstract

The composition and range of existence of aggregates formed by sodium taurocholate in aqueous micellar solutions were studied. Electromotive force measurements were used to obtain concentrations of free hydrogen and sodium ions. Experimental data obtained at 25 degrees C and at three N(CH3)(4)Cl concentrations, used as anionic medium, can be explained by assuming the presence of aggregates with different compositions depending on the reagent concentrations and the ionic strength. Comparison with taurodeoxycholate shows wide differences. Protonated species of taurocholate are observed only at pH less than or similar to 5. At higher pH, the micellar aggregate distribution remains nearly constant at a given ionic medium concentration. As expected, the size of the micellar aggregates increases on increasing the ionic strength. A dimer is found at all concentrations of the ionic medium. All species found have aggregation numbers of anions in multiples of two. The affinity of sodium ions for micellar aggregates is greater than that of N(CH3)(4)(+) ions

Taurocholate and Taurodeoxycholate: Gel Formation and Protonation Constants

“…The same gel formation is favoured by high bile salt and hydrogen ion concentration. This conclusion agrees well with experiments carried out in previous researches 12,13 . The gel formation takes place more easily in TDC than in TC solutions.…”

“…From the protonation constants of the two investigated bile salts, it can be deduced that their protonation to form the corresponding acid takes place only at high hydrogen ion concentration (-log c H ≤ 2). Previously, it was found that the formation of protonated micellar species started at lower c H both for TDC (-log c H ≤ 7.5) and for TC (-log c H ≤ 4), respectively 12,13 .…”

“…This result agrees well with that obtained under the same experimental conditions in previously papers. Previously 12,13 , by employing as ionic medium (0.100, 0.200, 0.300, 0.400. 0.500 and 0.750 mol dm -3 ) N(CH 3 ) 4 Cl, gel formation was never observed.…”

The Influence of the Ionic Medium on the Behaviour of Sodium Glycocholate and Cholate Aqueous Solutions

“…measurements as a function of hydrogen ion and reagent concentration. [6][7][8][9][10][11] Reagent activity coefficients were kept constant, in spite of a wide change of concentrations, adopting the constant ionic medium method. 12 N(CH 3 ) 4 Cl at different concentrations was selected as an ionic medium considered inert.…”

“…In the investigations on the dihydroxycholanic salts, 6-8 W was 0.100, 0.200, 0.300, 0.400, 0.500, 0.600 and 0.750 mol dm -3 , while in the case of the trihydroxycholanic salts [9][10][11] , W was only 0.100, 0.500 and 0.800 mol dm -3 .…”