Determination of the nature of the interaction of calcium ions with amino acids by potentiometric titration

Abstract

In work on the basis of potentiometric titration, the features of interaction of Ca2+ calcium ions with amino acids (AС), which are involved in biochemical processes in the human body, are established. The regularities of the complexes formed in the «Ca2+-AC» system are studied theoretically by the example of mixtures of calcium nitrate with isoleucine (Ile), arginine (Arg), aspartic acid (Asn), glycine (Gly), alanine (Ala). The conditions for titration are chosen, under which the destruction of the complex occurs. By results, semiquantitative characteristics of the interaction of Ca2+ and the studied AС were established. It was shown that the stability of the complexes increases with increasing number of carboxyl groups –COOH and nitrogencontaining groups in the AС molecule (especially NH2 groups in the α-position), and with the increase in the length of the carbon skeleton of the molecule and the appearance of bulky substituents — decreases. Also, on the base of insertion of the new criteria δ are established comparative rates of lability of complexes. According to their lability, complexes of Ca2+ with these amino acids are located in the next order: δ (Ca2+ – Asp) < δ (Ca2+ – Ile) < δ (Ca2+ – Ala) < δ (Ca2+ – Arg) < δ (Ca2+ – Gly).