86513-62-4Relevant articles and documents
Influence of Na+ on DNA reactions with aromatic epoxides and diol epoxides: Evidence that DNA catalyzes the formation of benzo[a]pyrene and benz[a]anthracene adducts at intercalation sites
Fernando, Harshica,Huang, Chao-Ran,Milliman, Ann,Shu, Luchuan,LeBreton, Pierre R.
, p. 1391 - 1402 (2007/10/03)
Reactions of the benzo[a]pyrene (BP) and benz[a]anthracene (BA) metabolites, (±)-trans-7, 8-dihydroxy-anti-9, 10-epoxy-7, 8, 9, 10- tetrahydro-BP (BPDE), (±)-trans-3, 4-dihydroxy-anti-1, 2-epoxy-1, 2, 3, 4- tetrahydro-BA (BADE), (±)-BP-4, 5-oxide (BPO), and (±)-BA-5, 6-oxide (BAO), were examined under pseudo-first-order conditions at varying Na+ (2.0-100 mM) and native, calf thymus DNA (ctDNA) concentrations. In 0.2 mM ctDNA and 2.0 mM Na+, at a pH of 7.3, most BPDE, BADE, BPO, and BAO (87-95%) undergo DNA catalyzed hydrolysis or rearrangement. For BPDE and BPO, overall, pseudo- first-order rate constants, k, in 2.0 mM Na+ and 0.2 mM ctDNA are 21-72 times larger than values obtained without DNA. For BADE and BAO, the rate constants are less strongly influenced by DNA; k values in 0.2 mM ctDNA are only 9-12 times larger than values obtained without DNA. Kinetic data for BPDE, BPO, BADE, and BAO and DNA intercalation association constants (K(A)) for BP and BA diols which are model compounds indicate that K(A) values for BPDE and BPO in 2.0 mM Na+ are 6.6-59 times larger than those of BADE and BAO. The greater DNA enhancement of rate constants for BPDE and BPO, versus BADE and BAO, correlates with the larger K(A) values of the BP metabolites. DNA adducts, which account for less than 10% of the yields, also form. For BPDE in 0.20 mM ctDNA, k decreases 5.1 times as the Na+ concentration increases from 2.0 to 100 mM. Nevertheless, the DNA adduct level remains constant over the range of Na+ concentrations examined. These results provide evidence that, for BPDE in 0.20 mM DNA and 2.0 mM Na+, ctDNA adduct formation follows a mechanism which is similar to that for DNA catalyzed hydrolysis. The pseudo-first-order rate constant for adduct formation, k(Ad), given approximately by k(Ad) ? (k(cat, Ad)K(A)[DNA])/(1 + K(A)[DNA]), where k(cat, Ad) is a catalytic rate constant. For BADE, BPO, and BAO, the influence of varying DNA and Na+ concentrations on k values is similar to that for BPDE, and provides evidence that the formation of adducts follows the same rate law.
Structures of Covalent Nucleoside Adducts Formed from Adenine, Guanine, and Cytosine Bases of DNA and the Optically Active Bay-Region 3,4-Diol 1,2-Epoxides of Benzanthracene
Cheh, Albert M.,Chadha, Anju,Sayer, Jane M.,Yeh, Herman J. C.,Yagi, Haruhiko,et al.
, p. 4013 - 4022 (2007/10/02)
Chemical structures of the principal covalent adducts formed from DNA upon reaction in vitro with the four optically active 3,4-diol 1,2-epoxides of benzanthracene have been elucidated at the nucleoside level.In addition to adducts formed by cis and trans addition of the exocyclic amino groups of deoxyadenosine (dA) and deoxyguanosine (dG) and a trans deoxycytidine (dC) adduct, chemical characterization of a deglycosylated N-7 dG adduct formed in DNA by trans opening of the (4S,3R)-diol (2R,1S)-epoxide isomer is reported.Relative stereochemistries of the adducts (cis versus trans opening of the epoxides by the exocyclic amino groups) were deduced from the coupling constants of the methine protons of the tetrahydro benzo rings of the acetylated derivatives.Adducts having (S)-configuration at the attachment site on the hydrocarbon moiety have CD spectra that exhibit a positive band at 250-260 nm and a negative band at longer wavelengths, whereas (R)-configuration at this center gives rise to CD spectra with bands of approximately equal intensity and opposite sign.This allowed assignment of cis versus trans addition to the chiral epoxides for adducts that were not generated in sufficient quantity to obtain NMR spectra.Analysis of the patterns of adducts derived from benzanthracene, benzophenanthrene, and benzopyrene shows that the comparative tumorigenicities of the diol epoxide isomers of each hydrocarbon do not correlate well with the extent of adduct formation, the ratio of cis versus trans addition to the epoxide, the propensity for forming adducts at dC or the N-7 position of dG, or the ratio of adduct formation at dA versus dG, although tumorigenicity may correlate with the ability to form dG adducts with (S)-configuration at the N-substituted benzylic carbon, especially those arising from trans addition to the epoxide.
