Analysis of benzo[a]pyrene diol epoxide-DNA adducts by capillary zone electrophoresis- electrospray ionization-mass spectrometry in conjunction with sample stacking
✍ Scribed by An V. Willems; Dieter L. Deforce; Elfriede G. Van den Eeckhout; Willy E. Lambert; Carlos H. Van Peteghem; André P. De Leenheer; Jan F. Van Bocxlaer
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 215 KB
- Volume
- 23
- Category
- Article
- ISSN
- 0173-0835
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✦ Synopsis
Abstract
Benzo[a]pyrene diol epoxide (BPDE) was reacted in vitro with (2'‐deoxy)nucleotides and with calf thymus DNA. The modified DNA was enzymatically hydrolyzed to the 5'‐monophosphate nucleotides using deoxyribonuclease I (DNA‐ase I), nuclease P1 and snake venom phosphodiesterase (SVP). Most of the unmodified nucleotides were removed using solid phase extraction (SPE) in a polystyrene divinylbenzene copolymer. Three adducts could be detected and identified using capillary zone electrophoresis(negative)‐ion electrospray ionization‐mass spectrometry (CZE‐(—)‐ESI‐MS) in conjunction with sample stacking. This way, not only a BPDE‐dGMP adduct [(M—H)^—^ at m/z 648], a well‐known nucleotide adduct, could be retrieved, but also a BPDE‐dAMP [(M—H)^—^ at m/z 632] and a BPDE‐dCMP adduct [(M—H)^—^ at m/z 608] could be detected for the first time. The presence of the prominent ion at m/z 195 (the deoxyribose‐phosphate ion) in the three low‐energy collision‐activated decomposition (CAD) spectra indicated that the adducts were formed through base‐alkylation. CZE‐positive ion ESI‐MS/MS experiments were performed to obtain further information on base‐alkylation. The absence of the loss of NH~3~ from the nucleobase in each CAD spectrum points to an alkylated exocyclic NH~2~ position of the nucleobase. So, the three adducts could be identified as BPDE‐N^2^‐dGMP, BPDE‐N^6^‐dAMP and BPDE‐N^4^‐dCMP using CZE‐ESI‐MS and CZE‐ESI‐MS/MS.