Myoglobin as an Efficient Electrocatalyst for Nitromethane Reduction

Abstract

Xenobiotic metabolizing heme enzymes are thought to take a crucial part in the activation of a variety of carcinogens, including nitro compounds, through catalytic electron-transfer reactions, especially under anaerobic conditions. Myoglobin (Mb), as a model heme enzyme, is found to act as an efficient electrocatalyst for the reduction of nitromethane in thin surfactant films on pyrolytic graphite electrodes. The electrocatalytic process is characterized by cyclic voltammetry. The Mb-Fe(II)-nitrosomethane complex, a possible intermediate in the catalysis, is characterized spectroscopically in the surfactant film on indium tin oxide electrodes. Bulk electrolysis indicates the formation of mainly methylhydroxylamine as an end aqueous product. A rationale for the catalysis invokes the highly reduced Fe(I) state of myoglobin in surfactant film; the latter engages in efficient inner-sphere electron transfers to the nitro compound coupled to proton transfers.

Functional Layer-by-Layer Thin Films of Inducible Nitric Oxide (NO) Synthase Oxygenase and Polyethylenimine: Modulation of Enzyme Loading and NO-Release Activity

“…The voltammogram shows two heme-based redox couples of iNOSoxy: the first corresponds to redox couple Fe 3+ /Fe 2+ and the second corresponds to the further reduction of Fe 2+ . Although this second reduction is not of importance in the electrochemical characterization of PEI/iNOSoxy in this work, we note that this behavior is typical of NOS oxygenases as well as other heme proteins that we investigated in the past. , …”

“…NOS oxygenases are redox active. Prior work in our lab has shown that films of iNOSoxy and nNOSoxy can exchange electrons with an underlying electrode. , Therefore, electrochemical analysis of PEI/iNOSoxy films on PG electrodes can be used to provide an estimate of overall amount of iNOSoxy adsorbed on PEI. This method offers us with an independent way to compare and contrast enzyme loadings for immobilizations conducted at pH 8.6 and 7.0.…”

“…Although this second reduction is not of importance in the electrochemical characterization of PEI/iNOSoxy in this work, we note that this behavior is typical of NOS oxygenases as well as other heme proteins that we investigated in the past. 27,28 To quantify the amount of iNOSoxy adsorbed on the PEI layer under the various LbL conditions, we performed numerical integration of the reduction current of Fe 3+ to Fe 2+ for voltammograms recorded at a slow scan rate (8 mV/s). For this work, to avoid surface variability from electrode to electrode, we have compared voltammograms for films built under the two pH conditions for the same electrode.…”

CASPT2 Study of the Decomposition of Nitrosomethane and Its Tautomerization Reactions in the Ground and Low-Lying Excited States

“…Nitroso compounds are of relevant importance as a result of their broad range of applications, such as synthetic reagents, spin trapping compounds, or high-energy materials . Nitrosoalkanes are biochemically important as well, for example, they form stable complexes with Fe III heme enzymes after the biodegradation of aliphatic nitroalkanes, a process which seems to be involved in the carcinogenic activity of the nitro compounds …”