TOXI 137 |
| In this study, we investigate effects of the arachidonic acid peroxyl radicals on the fates and end-products of the guanine neutral radicals, which are the primary products of the free radical attack on DNA. These radicals were generated by oxidation of the guanine and arachdonic acid by photochemically generated sulfate radicals in air-equilibrated solutions and monitored by transient absorption spectroscopy. The oxidatively modified nucleosides, separated and purified by HPLC analysis were identified by LC-MS/MS techniques. The major products found were the diastereomeric spiroiminodihydantoin, 5-diamino-4H-imidazolone (Iz) and dehydroguanidinohydantoin (Gh-ox) nucleosides. We found that ratio of the Iz/Gh-ox products depends on the photoexcitation mode. Continuous irradiation with 300 – 340 nm light from a 100W Xe arc lamp produces the Iz and Gh-ox nucleosides in close yields; however, a single-shot excitation with the 308 nm intense nanosecond excimer laser pulse generates mostly ther Iz products. The mechanistic aspects of the arachdonic acid peroxyl radicals on the fates and end products of guanine neutral radicals are discussed in detail. |
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General Papers
1:00 PM-4:45 PM, Wednesday, August 22, 2007 BCEC -- 258C, Oral
Division of Chemical Toxicology |