Thymidine Hydroperoxides: Structural Assignment, Conformational Features, and Thermal Decomposition in Water

Oxidative Processes and Antioxidative Metaloenzymes

“…A microsomal NADH oxidase was implicated as an oxygen sensor in bovine pulmonary and coronary arteries, where changes in oxygen tension regulate vascular relaxation through changes in O2 •-production and cGMP formation [198]. Increased aortic adventitial O2 •-production contributes to hypertension by blocking the vasodilatatory effects of NO • [189]. There is a strong possibility that rac-like proteins also occur in plants [1,193], where they may be involved in the induction of NAD(P)H oxidase-like enzymes [167].…”

“…Oxygen reacts with the allyl radical, producing 5-hydroxymethyluracil and 5-formyluracil. Thymine peroxyl radicals are reduced, and then protonated to give hydroxyperoxides [189], which break down to yield thymine glycol, 5-hydroxymethyluracil, 5-formyluracil, and 5-hydroxy-5-methylhydantoin [189].…”

Effect of Oxidative Stress on DNA Repairing Genes

“…Addition of O 2 to the allyl radical leads to 5-OHMeUra and 5-formyluracil (5-FoUra). Pyrimidine peroxyl radicals are also reduced and then protonated to give hydroxyhydroperoxides [Teoule, 1987], which decompose and yield thymine glycol, 5-OHMeUra, 5-FoUra, and 5-hydroxy-5-methylhydantoin [Wagner et al, 1994, Dizdaroglu et al, 1993a. Cytosine products may deaminate and dehydrate.…”

“…Cytosine glycol deaminates to give uracil glycol, 5-hydroxycytosine (5-OH-Cyt), and 5-hydroxyuracil (5-OH-Ura) that are unique in that they can deaminate and dehydrate. However, there is evidence that these four compounds (cytosine glycol, uracil glycol, 5-OH-Cyt, and 5-OH-Ura) may simultaneously be existed damaged DNA [Wagner et al, 1994, Dizdaroglu et al, 1993a. In the absence of O 2 , C5-OH adduct radicals may be reduced, followed by protonation to give rise to 5-hydroxy-6-hydropyrimidines.…”

Hidroperóxido de timina como fonte biológica de oxigênio molecular singlete [O2 (1Δg)]

“…Estes hidroperóxidos são comprovadamente estáveis em pH neutro, pois possuem altos valores de meia-vida de decomposição (Wagner, et al, 1994). Embora sejam peróxidos estáveis, os hidroperóxidos de timina e timidina podem decompor facilmente na presença de metais de transição (Tofigh e Frenkel, 1989) ou sob aquecimento (Wagner, et al, 1994).…”