ANALYSIS OF URACIL IN DNA BY GAS CHROMATOGRAPHY-MASS SPECTROMETRY

A sensitive method using gas chromatography and negative chemical ioni zation mass spectrometry for the detection of uracil in DNA is describ ed. Uracil DNA glycosylase is used to specifically cleave uracil from DNA. Once removed, uracil is derivatized with 3,5-bis(trifluoromethyl) benzyl bromide and the sample components are separated with gas chroma tography. Negative chemical ionization mass spectrometry is used to qu antitatively detect as little as 1 pg of uracil per 100 pg DNA. This a ssay is 10 times more sensitive than previously described quantitative methods for the detection of uracil in DNA. We apply this method as p art of a project to determine why folic acid deficiency causes DNA bre aks. We demonstrate that inhibition of folic acid metabolism induces a n accumulation of uracil in DNA. (C) 1994 Academic Press, Inc.