Oxidative damage to proteins mediated by singlet oxygen

Abstract

Singlet oxygen oxidizes tip residues in proteins into N-formylkynurenine and related products, just as peroxide does. It oxidizes tyr residues as well, but not to bityrosine or dihydroxyphenylalanine, as peroxide is able to do. His residues are oxidized by singlet oxygen, and the products appear to be more acidic. His oxidation in proteins also leads to covalent cross-linking of the protein, as monitored by the presence of higher molecular weight products in electrophoregrams. Blocking of his by adduct formation with diethylpyrocarbonate leads to inhibition of cross-linking. The oxygen molecule normally occurs in its ground electronic state with a spin multiplicity of three, or in the triplet state. From here, it can be excited to the singlet state, either to the 1A state or the higher 12 state, as shown in Figure 1. Table 1 highlig ts some facts about the singlet state of molecular oxygen.