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Studies of metabolic enzyme inhibition are necessary in drug development and toxicity investigations as potential tools to limit or prevent appearance of deleterious metabolites formed, for example, by cytochrome (cyt) P450 enzymes. In this paper, we evaluate the use of enzyme/ DNA toxicity biosensors as tools to investigate enzyme inhibition. We have examined DNA damage due to cyt P450cam metabolism of styrene using DNA/enzyme films on pyrolytic graphite (PG) electrodes monitored via [Ru(bpy).sub.3.sup.2+]-mediated DNA oxidation. Styrene metabolism initiated by hydrogen peroxide was evaluated with and without the inhibitors, imidazole, imidazole-4-acetic acid, and sulconazole (in micromolar range) to monitor DNA damage inhibition. The initial rates of DNA damage decreased with increased inhibitor concentrations. Linear and nonlinear fits of Michaelis--Menten inhibition models were used to determine apparent inhibition constants [K.sub.I.sup.*]) for the inhibitors. Elucidation of the best fitting inhibition model was achieved by comparing correlation coefficients and the sum of the square of the errors (SSE) from each inhibition model. Results confirmed the utility of the enzyme/ DNA biosensor for metabolic inhibition studies. A simple competitive inhibition model best approximated the data for imidazole, imidazole-4-acetic acid and sulconazole with [K.sub.I.sup.*] of 268.2, 142.3, and 204.2 [micro]M, respectively.

Redox chemistry in semisolid molten salts ionic liquids of DNA is described in which counterions of the phosphates are redox-active metal complexes with bipyridine ligands labeled with MW 350 poly-(ethylene glycol) (PEG) 'tails. Other redox metal complexes were added to the M(bpy(sub 350) DNA melt: (a) the PEG-tailed metal bipyridine complexes Fe(bpy(sub 350))(sub 3)(ClO(sub 4))(sub 2) and Ru(bpy(sub 350))(sub 3)(ClO(sub 4))(sub 2) and (b) the nontailed complexes Os(bpy)(sub 3)Cl(sub 2) (bpy =2,2'-bipyridine) and Os(bpy)(sub 2)dppzCl(sub 2).

Indium tin oxide (ITO)-Ru(bpy)(sub 3)(super 2+) system provides a convenient platform for studying electrocatalytic oxidation of DNA-solubilized carbon-nanotubes (CNTs), which are surprisingly effective electron donors. The convenience of the Ru(bpy)(sub 3)(super 2+)-ITO system should allow for detailed study of these properties and a rigorous description of the CNT oxidation reaction.