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Identification of phosphoramide mustard/DNA adducts using tandem mass spectrometry
Author(s) -
Cushnir Julia R.,
Naylor Stephen,
Lamb John H.,
Farmer Peter B.,
Brown Nigel A.,
Mirkes Philip E.
Publication year - 1990
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1290041014
Subject(s) - chemistry , tandem mass spectrometry , adduct , chromatography , mass spectrometry , tandem , identification (biology) , organic chemistry , botany , materials science , composite material , biology
The reaction pathway of alkylating agents is often exploited in the design of bifunctional anti‐cancer drugs. These drugs form mono‐DNA adducts as well as inter‐ and intra‐strand cross‐linked adducts, notably by reaction at DNA bases, including the N ‐7‐position of guanine (G). A positive‐ion fast‐atom bombardment (FAB) mass spectrum of an in vitro preparation of DNA alkylated with phosphoramide mustard (the active metabolite of the anti‐cancer drug cyclophosphamide) indicated the presence of the two mono‐DNA adducts N ‐(2‐chloroethyl)‐ N ‐[2‐(7‐guaninyl)ethyl] amine, designated NORG, and N ‐(2‐hydroxyethyl)‐N‐[2‐(7‐guaninyl)ethyl] amine, designated NORGOH, (MH + 257/259 and 239, respectively) but not the presence of the cross‐linked adduct N,N ‐bis‐[2‐(7‐guaninyl)ethyl] amine, designated GNORG (MH + 372). Using synthetic standards, daughterion spectra of NORG, NORGOH and GNORG were obtained (matrix 0.2 M p ‐toluene sulphonic acid in glycerol) by positive‐ion FAB tandem mass spectrometry (FAB‐MS/MS). The daughter‐ion spectra of both mono‐DNA adducts NORG and NORGOH contained a fragment ion at m/z 152 [G + H] + , whereas the cross‐linked adduct, GNORG, showed an ion at m/z 221, [MH − G] + . Evidence for the presence of NORG, NORGOH and GNORG in the in vitro preparation was obtained by performing a double parent‐ion scan on m/z 152 and 221. The presence of GNORG was further supported by performing a single parent‐ion scan on m/z 221. The use of this MS/MS technique should eliminate the need for intricate sample purification in the identification of GNORG in biological extracts.