Alkylation of DNA invivo - Development of analytical methodology for trace quantitative-analysis

Abstract

permitted identification of phenytoin and several of its metabolites.Supported by NIH Grant #GM36143. References[11 Markey, S. P., and Abramson, F. P., J. Chromatogr, 235, 523 (1982).[2] Abranson, F. P., and Markey, S. P., Biomed. Env. Mass Spectrom. 13, 411 (1986 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 isotope-or 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 N 2 , 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 5 NO 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

Mass spectrometry for the analysis of carcinogen‐DNA adducts

“…An important variation on this general method has been described by Cooks and co-workers (42,43). They advocate the importance of tandem mass spectrometry as well as the use of isotope dilution for quantification.…”

“…Since methylation of DNA can occur at primary oxygen or secondary nitrogen atoms on several bases, a complex mixture of methylated adducts, including positional isomers, can be expected in DNA. Studies on methylated dGuo derivatives using triple quadrupole MS and collision energies in the range of 15-20 eV typify this application (42,122,123). Ashworth et al (122) developed a tandem MS method capable of characterizing 15 different modified deoxynucleosides.…”

Building mass spectrometers and a philosophy of research

“…The thermolysis step used to convert RNA to fragments suitable for ionization caused unsuspected isomerization. Only much later, by using enzymatic degradation and a combination of LC and MS/MS, did we succeed in quantitating trace levels of modified nucleosides in mixtures [45].…”