A potentiometric study of some solution equilibria involving biological ligands and transition metal ions

Abstract

The formation constants for several metal ion-ligand complexes have been measured by glass electrode potentiometry in aqueous solution at 37°C using an ionic background of 150mM sodium perchlorate. The three topics comprising this thesis are (i) a study of the reaction of several metal ions, namely Co(II), Ni(II), Cu(II) and Zn(II), with ligands such as adeninate, cyclohexylamine and cyclopentylamine. These were studied in order to gain experience in the techniques of potentiometry and computation. (ii) The second topic, which comprises the major portion of the thesis, involved the in vitro study of zinc complexes with a series of ligands which can be divided into two groups; those containing only oxygen donor groups (acetate, galacturonate, hydroxybutyrate, malate, malonate, oxalate, salicylate and tartarate) and those which contain oxygen and nitrogen donor groups (glycinate, glycylglycinate and glycylglycylglycinate); the purpose of this investigation being to suggest the best zinc supplementing drug for treating zinc deficiency conditions. Hydroxybutyrate and galacturonate are suggested to be the most promising ligands for zinc absorption. (iii) Finally, computer simulation models of equilibria involving zinc and ligands in intestinal solution were used to correlate the rate of growth of turkey poults with the type of metal-ligand complexing occurring in intestinal fluid.