Chan Wan, Yue Hao, Wong Ricky N S, Cai Zongwei
Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Kowloon, Hong Kong SAR, China.
Rapid Commun Mass Spectrom. 2008 Dec;22(23):3735-42. doi: 10.1002/rcm.3791.
Metabolic activation of carcinogenic aristolochic acids (AA) produces reactive aristolactam-nitrenium ion intermediates. Electrophilic attack of the aristolactam-nitrenium ion via its C7 position to the exocyclic amino group in the purine bases leads to the formation of DNA adducts. DNA-binding assays have demonstrated that carcinogens show site- and sequence-specificity and the biological consequence is defined by the nature of binding as well as their position in the genome. In this study, electrospray ionization tandem mass spectrometry was applied for the identification and position mapping of DNA adducts in oligonucleotides (ODNs). The developed method was successfully applied for the analysis of unmodified and AA-modified ODNs (5'-TTTATT-3', 5'-TTTGTT-3' and 5'-TACATGTGT-3'). The observation of the modified bases (modified adenine and guanine) together with the complementary product ions (a(n)-B*(n), w(-)) from the cleavage of the 3' C--O bond adjacent to the modified base in MS/MS analyses readily enabled the identification of the AA-binding site in ODNs.
致癌性马兜铃酸（AA）的代谢活化会产生具有反应活性的马兜铃内酰胺-氮鎓离子中间体。马兜铃内酰胺-氮鎓离子通过其C7位对外环嘌呤碱基中的氨基进行亲电攻击，从而导致DNA加合物的形成。DNA结合试验表明，致癌物具有位点和序列特异性，其生物学后果由结合性质及其在基因组中的位置决定。在本研究中，电喷雾电离串联质谱被用于鉴定和定位寡核苷酸（ODN）中的DNA加合物。所开发的方法成功应用于未修饰和AA修饰的ODN（5'-TTTATT-3'、5'-TTTGTT-3'和5'-TACATGTGT-3'）的分析。在MS/MS分析中，观察到修饰碱基（修饰的腺嘌呤和鸟嘌呤）以及来自修饰碱基相邻3' C--O键断裂产生的互补产物离子（a(n)-B*(n)，w(-)），这使得能够轻松鉴定ODN中AA的结合位点。
