Electrochemical Properties of Active Groups

In the case of polarographic reduction of deuterohemin in O.l-KOH two waves are observed with EhO,i/2 = -0.36 V and -1.16 V, which correspond to the reduction of the central Fe ion and the ligand, respectively. Half-wave potentials for the reduction of Fe are observed to decline in the series proto- hemato- meso- deuterohemin. This shift reflects the variation of electron density at the central atom. 

These data, similarly to the results pertaining to other metallopor-phyrins, provide evidence for the reversible character of the redox transformations on electrodes. 

Electrochemical transformations of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) have been dealt with in several publications, since they are the most important hydrogen carriers. There are reviews on this topic/ The standard redox potential of the NAD(P)H/NAD(P) couple has been found to be —0.32 

An important role of adsorption during the reduction of NAD has been emphasized. Reduction of the pyridine ring in NAD on a gold electrode takes place at more positive potentials compared to those in the case of nicotinamide mononucleotide (NMN ) and nicotinamide. This is due to strong adsorption of the adenine part of NAD on the electrode surface. 

In order to accelerate electrooxidation of NADH, attempts are being made to develop chemically modified electrodes. Positive effects have been observed in the case of glassy carbon modified with 3,4-dihydroxybenzyl- 

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