Application of capillary gas chromatography-mass spectrometry to chemical characterization of radiation-induced base damage of DNA: implications for assessing DNA repair processes

The application of capillary gas chromatography-mass spectrometry (GC-MS) to the chemical characterization of radiation-induced base products of calf thymus DNA is presented. Samples of calf thymus DNA irradiated in N2O-saturated aqueous solution were hydrolyzed with HCOOH, trimethylsilylated, and subjected to GC-MS analysis using a fused-silica capillary column. Hydrolysis conditions suitable for the simultaneous analysis of the radiation-induced products of all four DNA bases in a single run were determined. The trimethylsilyl derivatives of these products had excellent GC properties and easily interpretable mass spectra; an intense molecular ion (M+.) and a characteristic (M-CH3)+ ion were observed. The complementary use of t-butyldimethylsilyl derivatives was also demonstrated. These derivatives provided an intense characteristic (M-57)+ ion, which appeared as either the base peak or the second most intense ion in the spectra. All mass spectra obtained are discussed