A CARBON-CENTERED RADICAL AS A REACTION SPECIES IN THE DNA STRAND-BREAKAGE BY D-GLUCOSAMINE

Electron spin resonance(ESR) studies using 5,5-dimethyl-1-pyrroline N- oxide (DMPO) and sodium 3,5-dibromo-4-nitrosobenzensulfonate (DBNBS) a s a spin-trapping agent revealed the formation of both hydroxyl and ca rbon-centered radical-derived spin adducts in Cu2+-containing 50 mM Tr is-HCl buffered solutions (pH 7.1) of D-glucosamine, D-mannosamine, an d D-galactosamine, which were previously shown to have the ability to break the single-strand of plasmid pBR322 DNA in a nucleotide sequence -specific manner. HCl-free D-glucosamine has higher DNA breaking activ ity, and this activity is promoted more by the presence of Cu2+ than t he original D-glucosamine hydrochloride, exhibits stronger radical sig nals in the ESR spectrum. It is suggested that D-glucosamine is unstab le around neutral pH, being converted into certain intermediate(s) suc h as a dihydropyrazine compound, which generate(s) carbon-centered rad icals, and that, besides the hydroxyl radical, the intermediate(s) is/ are responsible for DNA strand breakage.