Hemin- and Hemeprotein-Catalyzed Electroreduction of Aliphatic Nitro-Compounds

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Abstracts of Papers of The American Chemical Society


Some aliphatic nitro-compounds, such as nitromethane, are recognized as potential carcinogens. They are widely used and it is well established that they are involved in the development of serious health problems upon chronic exposure. Activation of these compounds and generation of reactive metabolites may be a pathway for their potential carcinogenesis. The activation of nitro-compounds is believed to be catalyzed by P450-type xenobiotic metabolizing heme-enzymes through electron transfer. Previous investigations in this laboratory showed that myoglobin immobilized in surfactant thin films on pyrolytic graphite electrode exhibits electro-catalytic activity for the reduction of nitromethane. In this work, we use electrochemical and spectroscopic techniques to characterize, compare, and contrast the catalytic activation of a number of aliphatic compounds, including a series of linear versus branched ones, by hemin and myoglobin in thin films on pyrolytic graphite electrodes. We will highlight the differences in reactivities between bare hemin versus hemin within a protein shell (i.e. a hemeprotein). Hemin- and myoglobin-mediated electrocatalytic activations will also be explored as a function of the size and structure of the nitroalkane substrates as well as other experimental parameters such as pH. Results will be presented and discussed in light of some proposed mechanistic pathways.