0000000000055982
AUTHOR
Ingrid Pontén
Critical parameters for adduct formation of the carcinogen (+)-anti-benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide with oligonucleotides.
Various parameters relevant for the formation of dG adducts produced in the reaction of individual benzo[a]pyrene diol epoxide (BPDE) stereoisomers with oligonucleotides have been studied. Reaction time, temperature, pH, molar ratio of diol epoxide and oligonucleotide, base sequence, and buffer system were shown to affect the amount of (+)-anti-BPDE dG adducts formed. Optimum experimental conditions for dG adduct formation were different depending on the base sequence context of the oligonucleotide employed [5'-d(CCTATAGATATCC) or 5'-d(CCTATTGCTATCC)]. In general, low temperature to allow a longer reaction time, slightly alkaline Tris-HCl (pH 7.5-8.0) or alkaline phosphate buffer (pH 11), l…
Synthesis and Characterization of Adducts Derived from the syn-Diastereomer of Benzo[a]pyrene 7,8-Dihydrodiol 9,10-Epoxide and the 5‘-d(CCTATAGATATCC) Oligonucleotide
5'-d(CCTATAGATATCC) was reacted with each syn-enantiomer of trans-7,8-dihydroxy 9,10-epoxy 7,8,9,10-tetrahydrobenzo[a]pyrene (syn-BPDE). The (-)-enantiomer yielded one dominating adduct, whereas the (+)-enantiomer resulted in two major adducts. As indicated by optical spectroscopic methods, the major adduct derived from both (-)- and (+)-syn-BPDE involves cis addition of the C-10 position of the diol epoxide to the exocyclic amino group of deoxyguanosine [(-)-syn-BPDEc-N2-dG and (+)-syn-BPDEc-N2-dG, respectively], whereas the minor (+)-syn-BPDE adduct is identical to a trans adduct [(+)-syn-BPDEt-N2-dG]. The cis adducts as well as the (+)-syn-BPDEt-N2-dG adduct are chemically stable for sev…
Spectroscopic Studies of Oligonucleotide Adducts and Base Sequence Preference of Adducts Formed by the Stereoisomers of 7,8-Dihydroxy-9,10-epoxy-7,8,9,10-Tetrahydrobenzo[a]pyrene
Abstract 5′-d(CCTATAGATATCC) has been reacted with BPDE and the adducts derived from binding of BPDE to the exocyclic amino group of deoxyguanosine (dG) were studied with spectroscopic methods. The major dG-adducts of (+)- and (-)-anti-BPDE and a minor adduct of (+)-syn-BPDE showed the characteristics of trans-adducts. The major products formed with (+)- and (-)-syn-BPDE exhibit cis-adduct characteristics. Annealing of BPDE-modified oligonucleotides to complementary or partially complementary strands results in reduced fluorescence intensity in several cases and in others the intensity is markedly increased. These differences demonstrate that the adduct microenvironment is strongly influenc…