Oxidation by Hydroxyl Radical and hydrogen atoms

Reactions of hydroxyl radical are of particular importance because of theii probable involvment in many pathological processes related to oxidative stress. 

Rate constants of reactions of e aq with some amino-acids and proteins. 

Data are taken from G. V. Buxton, C. L. Greenstock, W. P. Helman and A. B. Ross, J. Phys. Chem. Ref. Data 17 (1988) 513. 

OH radicals would be produced in vivo mostly by the Fenton system (Fe2+ + H2O2) (5). Reactions of H atom are poorly known compared to those of OH however, they are believed to have similar mechanisms. 

OH free radicals do not react with the peptidic bond, but they may withdraw an H atom to the a-carbon. In the absence of oxygen, the fate of this free radical is not well known. In amino-acids, decarboxylation occurs (37), thus it might end up with protein fragmentation. In the presence of oxygen, a peroxyl radical is 

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