11] Preparation of chromium(III) and cobalt(III) nucleotides as chirality probes and inhibitors

Abstract

This chapter describes the preparation and properties of Co(III)- and Cr(III)-nucleotide complexes, and how they can be used to determine enzymic specificity. Before describing the preparation of complexes, the chapter reviews their stereochemistry and the types of isomerization that occur. The consideration is limited to complexes between phosphate oxygens and metal ion, since all of the complexes to be described are of that type. There are two methods described for synthesis of complexes: heating method and titration method. In heating method, a solution 10 mM is heated each in nucleotide and metal ion at 80°C for various times. Titration procedure converts monodentate CrATP cleanly in at least 90% yield to bidentate CrATP. Cr(III)-[and in some cases, Co(Ill)-] nucleotide complexes are usually excellent inhibitors of enzymes using Mg-nucleotide complexes as substrates, since their activities as substrates are normally very low, and thus they are useful as dead-end inhibitors of enzymic reactions in kinetic studies of mechanism, or for inducing suitable conformation changes without rapid turnover.