Modification of Biomacromolecules with Six-valent Osmium Complexes and Electrochemical Analysis of the Modified Products

Abstract

This review is focused on the reaction of 1,2-diols with ligand complexes of six-valent osmium [Os(VI)L] (where L is a nitrogenous ligand) and possibilities of electrochemical analysis of yielded products. A number of biologically important molecules, such as mono-, oligo- and polysaccharides, RNA and glycoproteins, belong to compounds containing 1,2-diol in their structure. These compounds react with Os(VI)L yielding relatively stable ligand osmate esters which are electrochemically active and suitable to the electrochemical analysis. The ligand osmate esters give redox peaks at the mercury and carbon electrodes. The redox peaks are due to the electrochemical reduction or oxidation of osmium atoms. The osmate esters with some ligands give catalytic peaks at the mercury electrodes. The catalytic peak is due to the catalytic hydrogen evolution and is very sensitive. With the catalytic peak it is possible to measure picomolar concentrations in some cases. We have used reactions of Os(VI)L for the analysis of glycans and glycoproteins in relation to their great importance in biomedicine.