The equilibrium between carbon dioxide and bicarbonate, both of which are present in biological systems at millimolar concentrations, plays a key role in regulating physiological pH in mammals. Recent studies have shown that this buffer is involved in oxidation and nitration reactions of biological molecules. The carbonate radical anion (CO3��) is a potent oxidant generated from the one electron oxidation of HCO3�  at the active site of enzymes such as Cu, Zn-superoxide dismutase and by homolysis of nitrosoperoxycarbonate (ONOOCO2�), a species formed from the reaction of peroxynitrite with carbon dioxide. However, excessive production of reactive radical species can lead to oxidative stress, resulting in irreversible damage to biomolecules. Oxidative stress has been implicated in various pathological conditions involving cardiovascular disease, cancer, neurological diseases and aging. Therefore, the role of the carbonate radical anion in human disease and toxicology has become an area of considerable interest.Vitamin B12 complexes and its derivatives, also known as cobalamins (Cbls), are essential micronutrients in all living organisms, and are required as cofactors for two enzymes in mammals. Both mammalian B12-dependent enzymes are inactive under oxidative stress conditions. Cbls have been used as therapeutics for treating inflammatory diseases and there is accumulating evidence that the Cbls react rapidly with reactive oxygen and nitrogen species, including superoxide,nitric oxide, and nitrite. We recently showed that cobalamins protect against oxidative stress in a cellular model.In this study we present pulse radiolysis studies on the direct reaction of carbonate radical anion with two important vitamin B12 complexes - cob(II)alamin and cob(III)alamin. Interestingly, kinetic studies shows that both the reduced (cob(II)alamin) and the oxidized (cob(III)alamin) vitamin B12complexes react very rapidly with the carbonate radical anion.This research was supported by the US National Institute of General Medical Sciences of the National Institutes of Health and the U.S. DOE Office of Science, Division of Chemical Sciences, Geosciences and Biosciences.

Pulse radiolysis studies on the reactions of the carbonate radical with vitamin B<sub>12</sub> complexes

246th National Meeting (2013)

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Pulse radiolysis studies on the reactions of the carbonate radical with vitamin B12 complexes

Pulse radiolysis studies on the reactions of the carbonate radical with vitamin B₁₂ complexes