Optically detected magnetic resonance study of benzo[a]pyrene‐7,8‐dihydrodiol 9,10‐oxide covalently bound to DNA

Stereoselective covalent binding of enantiomers of anti-benzo[a]pyrenediol epoxide to DNA as probed by optical detection of magnetic resonance

“…The procedures for recording 77 K phosphorescence and ODMR spectra at 2 K have been reported previously (Lefkowitz et al, 1979). Briefly, samples were irradiated by the filtered output of a 100-W Hg lamp, and the phosphorescence was isolated with a rotating double-blade chopper phosphoroscope, used in combination with a lock-in amplifier.…”

“…In the last few years, optical detection of magnetic resonance (ODMR) has been employed as a probe of the structure of complexes of DNA with polycyclic aromatic hydrocarbon carcinogens (Chiha et al, 1977(Chiha et al, , 1978Lefkowitz et al, 1979; Lefkowitz & Brenner, 1981, 1982Clarke et al, 1983). As is well-known, the excited triplet state of an organic molecule 1 Abbreviations: BaPDE, trazis-7,8-dihydroxy-anr/-9,10-epoxy-7,8,9,10-tetrahydrobenzo[ajpyrene; BaPT,7,8,9,pyrene; BeP, benzo[e]pyrene; BePE,9,10,11,pyrene; DNA, deoxyribonucleic acid; EGB, ethylene glycol/buffer solution; GHz, gigahertz; MHz, megahertz; ODMR, optically detected magnetic resonance.…”

Distinct local environments of the pyrene chromophores in the covalent DNA adducts of 9,10-epoxy-9,10,11,12-tetrahydrobenzo[e]pyrene and 7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene elucidated by optically detected magnetic resonance

“…Phosphorescence and ODMR. The methods used for determining 77 K phosphorescence spectra and 2 K ODMR spectra (run at the appropriate phosphorescence maxima) have been described in detail (Lefkowitz et al, 1979). Phosphorescence decays at 77 K were measured by using right angle excitation with synchronously linked shutters for excitation and emission.…”

“…Since both the sublevel energy splittings and kinetic dif- ferentiation are very sensitive to the symmetry of the excited chromophore, we expect them to reflect any environmentally induced distortions of the unpaired electron density. Earlier ODMR studies yielded preliminary results, suggesting that the pyrene chromophore of the BePE-DNA adduct exhibits a substantial nucleic acid induced perturbation (Lefkowitz & Brenner, 1981), while the BaPDE adduct shows little evidence of interaction with DNA (Lefkowitz et al, 1979). In this paper we consolidate and amplify those studies and present evidence identifying the primary source of ODMR perturbation in the BePE adduct as the double-helical structure of DNA, indicative of some intercalative-like environment for this chromophore, while the BaPDE adduct's ODMR properties closely resemble those expected for the chromophore in the bulk solvent, suggesting little interaction with the tertiary DNA structure.…”

FLUORESCENCE SPECTROSCOPY OF BENZO[a]PYRENE DIOL EPOXIDE‐DNA ADDUCTS. CONFORMATION‐SPECIFIC EMISSION SPECTRA

“…Previous studies have implied that the presence of the glycol does not significantly affect the conformation of BPDE-DNA adducts at their binding sites; specifically, the angles of the BPDE-chromophore transition moments relative to the DNA helix axis, as measured by linear dichroism, do not change to any appreciable extent (A. Gagliano, personal communication), the DNA retains its duplex structure (Lefkowitz and Brenner, 1982), and the qualitative conclusions of optically detected magnetic resonance experiments at cryogenic temperatures in this solvent, regarding the predominance of site I or site I1 binding in several adducts, agree with the results of roo? temperature spectroscopic studies in aqueous buffer solutions (Lefkowitz and Brenner, 1982;Lefkowitz et al, 1979;Kolubayev, 1986;Kolubayev et al, 1987).…”