Mass Spectrometric Sequencing of Site-Specific Carcinogen-Modified Oligodeoxyribonucleotides Containing Bulky Benzo[a]pyrene Diol Epoxide–Deoxyguanosyl Adducts

Abstract

Site-specific carcinogen-modified oligonucleotides are often used in site-directed mutagenesis and other biological and biochemical studies of structure–function relationships. Postsynthetic analysis and confirmation of the sites of carcinogen binding in such oligonucleotides is an important step in the characterization of these site-specific carcinogen–DNA adducts. It is shown here that negative ion mode electrospray tandem mass spectrometry methods and collision-induced dissociation offer a rapid and convenient approach for the sequencing of products derived from the reaction of the carcinogenic and mutagenic metabolite of benzo[a]pyrene, the diol epoxider7,t8-dihydroxy-t9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE), with the 11-mer oligonucleotide d(CATGCGGCCTAC). The site of reaction ofanti-BPDE with either one of the three dG residues in this oligonucleotide can be accurately established by comparing the mass/charge ratios of the observed collision-induced dissociation fragments with calculated values.