Fragmentation patterns of DNA–benzo(a)pyrene diol epoxide adducts characterized by nanoflow LC/quadrupole time-of-flight mass spectrometry

Polycyclic aromatic hydrocarbons are a pervasive and abundant class of environmental and workplace pollutants. Formation of covalent DNA adducts has been considered to be a useful dosimeter or molecular biomarker for assessing the exposure to such pollutants. The establishment of prospective models for the formation of DNA adducts may help to understand the mechanisms of the effects. To identify the DNA adducts in this study, the fragmentation patterns of DNA–benzo(a)pyrene diol epoxide adducts were characterized by nanoflow liquid chromatography (LC) coupled to hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometry (Q-TOF-MS). In the experiment, the DNA adducts were synthesized by reaction of calf thymus DNA with anti-benzo(a)pyrene-r-7,t-8-dihydrodiol-t-9,10-epoxide(±) (anti-BPDE). The major adducts of N2-deoxyguanosine–benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (N2-dG–BPDE), N6-deoxyadenosine–benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (N6-dA–BPDE), N4-deoxycytidine–benzo(a)pyrene-7,8-epoxide (N4-dC–BPDE), and N3-deoxythymidine–benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide adduct (N3-dT–BPDE) were identified by electrospray positive ionization with TOF-MS/MS scan mode. The results of this study demonstrated that the approach that utilizes collision-induced dissociation leading to a characteristic fragmentation pattern offers a distinct advantage for identification and elucidation of molecular structural features of the DNA adducts. The fragmentation patterns established in this study may be applied to identify DNA adducts in biological systems.