QUANTITATIVE-DETERMINATION OF 8-HYDROXYGUANINE AND GUANINE BY ISOTOPE-DILUTION MASS-SPECTROMETRY

8-[4,5,6,8-C-13(4)]Hydroxyguanine and [4,5,6-C-13(3)]guanine were prep ared by total synthesis. The labeled compounds were used as internal s tandards in a gas-liquid chromatographic-mass spectrometric method for quantitative determination of 8-hydroxyguanine and guanine in DNA. Th e approach used made it possible to directly determine the ratio betwe en 8-hydroxyguanine and guanine, expressed as the number of molecules of 8-hydroxyguanine per 10(5) molecules of guanine, in the sample of D NA analyzed. A method for trimethylsilylation of 8-hydroxyguanine and guanine at room temperature was developed. Use of this method for deri vatization gave levels of 8-hydroxyguanine in calf thymus DNA which we re lower than those recently found by gas chromatography-mass spectrom etry but similar to those determined by high-performance liquid chroma tography with electrochemical detection. (C) 1995 Academic Press, Inc.