Cellular DNA is constantly being damaged by oxidation and alkylation, by free radicals, and by ultraviolet and ionizing radiation. The body has therefore evolved a number of repair enzyme systems to excise and repair these lesions. The 8-oxo purine monomers allow investigation of the structure and activity of oligonucleotides containing an 8-oxo mutation which is formed naturally when DNA is subjected to oxidative conditions or ionizing radiation. 5,6-Dihydro pyrimidines are naturally occurring compounds that are structural components of alanine transfer RNA. Dihydrouracil and the hydroxy pyrimidines are major base damage products formed by exposure of DNA to ionizing radiation.
Coupling: No changes needed from standard method recommended by synthesizer manufacturer.
Deprotection: Cleave and deprotect with ammonium hydroxide containing 0.25M 2-mercaptoethanol 17 hours at 55°C to avoid oxidative degradation of the 8-oxo-dG site.