Structural characterization of carcinogen-modified oligodeoxynucleotide adducts using matrix-assisted laser desorption/ionization mass spectrometry

✍ Scribed by Karen Brown; Chris A. Harvey; Kenneth W. Turteltaub; Sharon J. Shields

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 548 KB
• Volume: 38
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.401

✦ Synopsis

Abstract

The aim of this study was to determine the chemical structure of in vitro 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP)‐modified oligodeoxynucleotides (ODNs) by exonuclease digestion and matrix‐assisted laser desorption/ionization mass spectrometry. A single‐stranded 11‐mer ODN, 5^′^‐d(CCATCGCTACC), was reacted with N‐acetoxy‐PhIP, resulting in the formation of one major and eight minor PhIP–ODN adducts. A 10 min treatment of the major and one minor PhIP–ODN adduct with a 3^′^‐exonuclease, bovine intestinal mucosa phosphodiesterase (BIMP), and a 5^′^‐exonuclease, bovine spleen phosphodiesterase, results in inhibition of the primary exonuclease activity at deoxyguanosine (dG) producing 5^′^‐d(CCATCG(PhIP)) and 5^′^‐d(G(PhIP)CTACC) product ions, respectively. Post‐source decay (PSD) of these enzymatic end products identifies dG as the sole modification site in two 11‐mer ODN–PhIP adducts. PSD of the minor PhIP–ODN adduct digestion end product, 5^′^‐d(CCATCG(PhIP)), also reveals that the PhIP adducted guanine moiety is in an oxidized form. Prolonged treatment of the PhIP–ODN adducts at 37° C with BIMP induces a non‐specific, or endonuclease, enzymatic activity culminating in the formation of deoxyguanosine 5^′^‐monophosphate‐PhIP (5^′^‐dGMP–PhIP). The PSD fragmentation pattern of the 5^′^‐dGMP–PhIP [M + H]^+^ ion of the major adduct confirms PhIP binds to the C‐8 position of dG. For the minor adduct, PSD results suggest that PhIP binds to the C‐8 position of an oxidized guanine, supporting the hypothesis that this adduct arises from oxidative degradation, resulting in a spirobisguanidino structure. Copyright © 2003 John Wiley & Sons, Ltd.