On the formation of calcium(II) taurocholate aggregate species in aqueous solution

Abstract

The influence of the presence of calcium(II) ions in solutions containing sodium and taurocholate ions at 25 degrees C and in 0.5 mol dm(-3) N(CH(3))(4)Cl as the constant ionic medium was studied. The composition and existence range of aggregates formed by taurocholate sodium and calcium(II) were investigated by means of two different procedures. First, the increasing calcium oxalate solubility due to the presence of taurocholate ions was studied as a function of the taurocholate, sodium and hydrogen ions. The free concentration of sodium and hydrogen ions was determined in solutions equilibrated with solid calcium(II) oxalate. After filtration, the concentration of calcium(II) (by atomic absorption spectrophotometry) and that of oxalate were also determined. In the second approach, electromotive force measurements carried out in solutions containing taurocholate, sodium and calcium(II) ions provided hydrogen and sodium ions free concentrations. The results from both procedures could be explained by assuming the presence of aggregates of different composition with the participation of sodium, calcium(II) and taurocholate ions, depending on the concentration of the reagents. No protonated species were present in appreciable concentrations. All the species found have even anion aggregation numbers. A strong analogy with the composition of sodium taurocholate and glycocholate is observed, while a comparison with sodium deoxycholate, glycodeoxycholate and taurodeoxycholate shows wide differences

Solubility and the Solubility Product of Some Calcium(II) Salts of Bile Acids

“…Previous , studies carried out on solutions containing calcium(II) and taurocholate and taurodeoxycholate showed that no precipitate is formed in a wide range of concentration, but only aggregates with different compositions.…”

“…The formation of micellar aggregates of calcium(II), taurocholate (TC) and taurodeoxycholate (TDC), was investigated in previous papers. , It was found that both these salts are soluble and the composition of premicellar and micellar aggregates was found.…”

An investigation on calcium taurodeoxycholate micellar aggregates

“…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.…”

“…Then after considering the other variables can represent a good approximate solution. This procedure, as applied to the treatment of the experimental data, will be explained briefly because it is similar to that applied in the case of taurocholate (Antonilli et al, 2009).…”

“…More recently, the formation of calcium(II) taurocholate aggregate species in aqueous solution was studied and the results were explained by assuming the formation of aggregates containing both calcium and sodium ions together with taurocholate (Antonilli et al, 2009).…”