Alkylation of DNA In Vivo: Development of Analytical Methodology for Trace Quantitative Analysis

Markey and Abramson [1] developed a microwave-powered chemical reaction interface, a device which converts a complex organic molecule in the presence of a reactant gas into small stable molecules which are detected by mass spectrometry. For a given reactant gas the molecules formed are a representation of the elemental composition of the original anlayte. The combination of the reaction interface and a mass spectrometer produces an isotopeor element-selective detector for samples either introduced directly into the reaction interface or flowing from a capillary gas chromatograph column. Microgram and submicrogram samples of a variety of proteins were analyzed for their sulfur content relative to their carbon content by introducing the samples directly into the reaction interface. With CO, as the reactant gas, S02 at m/z 64 is produced. This quantifies the amount of sulfur which was introduced into the reaction interface. In the presence of N2, HCN at m/z 27 is produced and is used to quantify the carbon content of the sample. The observed ratio of S/C for various proteins correlated well with the elemental formulas [2]. In the presence of S02, 4NO at m Iz 30 and 5NO at m/z 31 are produced. Following administration of 50 mg of triple-labeled 5,5-diphenylhydantoin (1, 3("N); 2('C)] to a male beagle dog, a urine sample was selectively analyzed for its 15N content by capillary gas chromatography-reaction interface/ mass spectrometry. The corrected ratio of m/z 31 to m/z 30 produced a highly selective chromatogram showing only peaks of '5N enrichment. Mass spectra of these peaks were obtained which Alkylation of DNA In Vivo: Development of Analytical Methodology for Trace Quantitative Analysis