LIQUID-CHROMATOGRAPHY ELECTROSPRAY-IONIZATION TANDEM MASS-SPECTROSCOPY (LC ESI MS/MS) ANALYSIS OF 1,2-EPOXYBUTENE ADDUCTS OF PURINE DEOXYNUCLEOSIDES/

Calf thymus DNA was reacted with 1,2-epoxybutene (BDO) in phosphate bu ffered saline at 37 degrees C for 12 h. DNA was ethanol precipitated a nd hydrolyzed with 1 M HCI to release DNA bases. Adenine (A)-BDO and g uanine (Gua)-BDO adducts were analyzed in the ethanol supernatant and DNA hydrolysate using LC/ESI MS/MS. Reaction of BDO with A resulted in the formation of seven A-BDO adducts with MH(+) ions at m/z 206. Two of these adducts were observed in the ethanol supernatant. In addition , two formaidopyrimidine (FAPY)-adducts were detected with MH(+) ions at mit 224 in DNA hydrolysate. These data are consistent with formatio n of regioisomeric N-7 or N-9 adducts which can be released by spontan eous depurination or ring opening. Four other A-BDO adducts were detec ted in DNA hydrolysate. Similar adducts were observed for Gua. This ne w methodology permits simultaneous determination of initially formed a dducts as well as those arising as a consequence of depurination. The latter adducts provide the opportunity for monitoring exposure to BDO through analysis of N-7 or N-3 adducts excreted in the urine.