Oxidation of Dibenzothiophene Catalyzed by Hemoglobin and Other Hemoproteins in Various Aqueous-Organic Media |
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Authors: | Natalia L Klyachko Alexander M Klibanov |
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Institution: | (1) Department of Chemistry, Massachusetts Institute of Technology, 02139 Cambridge, MA |
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Abstract: | Biocatalytic oxidation of dibenzothiophene (a model of organic sulfur in coal) with hydrogen peroxide was investigated. It
was found that various hemoproteins, both enzymic (e.g., horseradish peroxidase) and nonenzymic (e.g., bovine blood hemoglobin),
readily oxidized dibensothiophene to its S-oxide and, to a minor extent, further to its S-dioxide (sulfone). This process
catalyzed by hemoglobin (a slaughterhouse waste protein) was studied in a number of monophasic aqueousorganic mixtures. Although
hemoglobin was competent as an oxidation catalyst even in nearly dry organic solvents (with protic, acidic solvents being
optimal), the highest conversions were observed in predominantly aqueous media. The hemoglobin-catalyzed oxidation of dibenzothiophene
at low concentrations of the protein stopped long before all the substrate was oxidized. This phenomenon was caused by inactivation
of hemoglobin by hydrogen peroxide that destroyed the heme moiety. The maximal degree of the hemoglobin-catalyzed dibenzothiophene
oxidation was predicted, and found, to be strongly dependent on the reaction medium composition. |
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Keywords: | Hemoglobin peroxidase coal desulfurization dibenzothiophene aqueous-organic media for biocatalysis biooxidations |
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