Composition of Sodium Glycocholate Micellar Solutions

Abstract

Composition and existence range of aggregates formed by sodium glycocholate in aqueous solutions were studied. Electromotive force measurements provided hydrogen, sodium, and glycocholate ion free concentrations. Lead(II) glycocholate solubility measurements yielded the free concentration of glycocholate ions, as well. Experimental data obtained at 25 °C and at three different concentrations of N(CH3)4Cl, used as a constant ionic medium, can be explained by assuming the presence of aggregates with different compositions, depending on reagent and ionic medium concentrations. The distribution of the species found at the same concentration of ionic medium and close to neutrality remains constant. As expected, the size of the aggregates increases by increasing ionic medium and reagent concentrations. A dimer is the prevailing species at low concentrations, and all of the found species have even anion aggregation numbers. In solutions with the highest concentration and ionic strength, aggregate multiples of eight are present at a high percentage. These results agree with structural investigations that proposed as building blocks of sodium glycocholate micellar aggregates a dimer and an octamer. A strong analogy with the composition of taurococholate aqueous solutions is observed. The comparison with deoxycholate, glycodeoxycholate, and taurodeoxycholate shows wide differences.

An investigation on calcium taurodeoxycholate micellar aggregates

“…Its value at 25 C and in 0.500 mol dm À 3 N(CH 3 ) 4 Cl, was found to be ¼ 58.3 mV (also in agreement with Bottari et al, 2002). E s II , a constant, was determined in the first part of each measurement, when only sodium ions were present, i.e.…”

“…As many other papers (Bottari and Festa, 2002, 2003, 2004Antonilli et al, 2009;Bonincontro et al, 2008;Bottari et al, 1999) on this subject demonstrated, the behaviour of dihydroxycholanic salts is different with respect to trihydroxycholanic salts, such as cholic, glycocholic and taurocholic, which form aggregates with lower aggregation number and even, having as building block a dimer or, for the bigger species, an octamer.…”

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

“…10 This work is focused to find q, p, and r values and the corresponding β q,p,r , previously defined. Also in this case, two different approaches were applied to study the association in solutions of NaGC and NaCol.…”

“…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 .…”