ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY AND HPLC DETERMINATION OF THE PRODUCTS IN THE RADIOLYSIS OF 5-BROMOURACIL, ITS NUCLEOSIDE AND NUCLEOTIDE DERIVATIVES

Radiolysis of 5-bromouracil (BrUr), 5-bromo-2'-deoxyuridine (BrdU) and 5-bromo-2'-deoxyuridine-5'-monophosphate (BrdUMP) has been studied by high performance liquid chromatography and electrospray ionization ma ss spectrometry. Production of bromide ions and the complementary urac il, 2-deoxyuridine and 2-deoxyuridine-5'-monophosphate has been quanti tatively examined. It is concluded that in the presence of hydroxyl ra dical scavenger, at pH 6 to 10, BrUr, BrdU and BrdUMP quantitatively r eact with hydrated electron. In the absence of hydroxyl radical (OH) s cavenger in N-2-saturated solutions the yield of bromide ions is about 5.0, indicating that hydroxyl radicals also significantly react with BrUr, BrdU and BrdUMP to eliminate hydrogen bromide. Results from the radiolysis of 1 mM aqueous solutions of BrdU and BrdUMP suggested that abstraction of hydrogen by uracilyl radicals from the sugar moieties is not important. Our mass spectrometry experiments indicated that ura cilyl radicals react with the starting substrate to form dimers. The r adiolysis of N-2-saturated solutions of nucleosides and nucleotides su ggested that the base radicals formed by OH addition can react with un damaged reagents to produce dimers.