Electrocatalysis in proteins, nucleic acids and carbohydrates

Abstract

The ability of proteins to catalyze hydrogen evolution has been known for more than 80 years, but the poorly developed d.c. polarographic "pre-sodium wave" was of little analytical use. Recently, we have shown that by using constant current chronopotentiometric stripping analysis, proteins produce a well-developed peak H at hanging mercury drop and solid amalgam electrodes. Peak H sensitively reflects changes in protein structures due to protein denaturation, single amino acid exchange, etc. at the picomole level. Unmodified DNA and RNA do not yield such a peak, but they produce electrocatalytic voltammetric signals after modification with osmium tetroxide complexes with nitrogen ligands [Os(VIII)L], binding covalently to pyrimidine bases in nucleic acids. Recently, it has been shown that six-valent [Os(VI)L] complexes bind to 1,2-diols in polysaccharides and oligosaccharides, producing voltammetric responses similar to those of DNA-Os(VIII)L adducts. Electrocatalytic peaks produced by Os-modified nucleic acids, proteins (reaction with tryptophan residues) and carbohydrates are due to the catalytic hydrogen evolution, allowing determination of oligomers at the picomolar level.

Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces

“…The CPS behavior of urease ( Fig. 1B-E) was found to be in agreement with our previous results [14][15][16][17] implying that the use of CPS for analysis of very large protein molecules and their complexes might be possible.…”

“…2A, peak S in Inset), probably followed by changes in the protein orientation at the surface. Moreover, prolonged exposure of the protein to negative potentials could lead to some electric field-induced changes in the protein conformation [14,15]. Both the changes in the orientation and in the structure of the surface-attached protein could result in inhibition of its enzymatic activity.…”

“…Recently we have shown that using constant current chronopotentiometric stripping (CPS) practically all proteins yield a well-developed peak H at mercury and solid amalgam electrodes [13][14][15][16][17]. This peak is due to the catalytic hydrogen evolution reaction (CHER) [18,19].…”

Direct chemical modification and voltammetric detection of glycans in glycoproteins

“…The fields of nucleic acid [1] and protein [2,3] electrochemistry are booming. Until recently electrochemical protein analysis focused predominantly on conjugated proteins containing non-protein redox centers [3].…”

Facile preparation of nanostructured copper-coated carbon microelectrodes for amperometric sensing of carbohydrates

“…1,2 Of the direct electrochemical methods, pulsed amperometric detection (PAD) at platinum or gold electrodes in alkaline media has attracted a lot of attention as a method that provides a sensitive response in carbohydrate analysis. Under specic conditions, carbohydrates can be measured electrochemically aer labelling with electroactive markers.…”