59957-91-4Relevant academic research and scientific papers
Laser-Induced Room-Temperature Phosphorescence Detection of Bnzopyrene-DNA Adducts
Vo-Dinh, Tuan,Uziel, Mayo
, p. 1093 - 1095 (1987)
The room-temperature phosphorescence (RTP) spectrum of benzopyrene-r-7,t-8,9,10-tetrahydrotetrol (BP-tetrol) has been measured using laser excitation.The BP-terol was obtained by acid hydrolysis of the r-7,t-8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzopyrene (BPDE)-DNA adducts.BPDE is the ultimate carcinogenic metabolite of benzopyrene (BP).The BP-tetrol sample was measured on a filter paper substrate pretreated with a heavy-atom salt, thallium acetate, used to increase the phosphorescence signal of BP-tetrol.The detection limit of BPDE in vitro modified BPDE-DNA was about 15 fmol.The results indicate the RTP would be useful as a simple and practical screening tool for monitoring BPDE-DNA adducts and related BP metabolites in biological samples.
Proton-coupled electron transfer in the oxidation of guanines by an aromatic pyrenyl radical cation in aqueous solutions
Kuzmin, Vladimir A.,Dourandin, Alexander,Shafirovich, Vladimir,Geacintov, Nicholas E.
, p. 1531 - 1535 (2000)
Electron transfer reactions between nucleic acid residues in DNA and strong oxidants are often the critical initial steps that initiate oxidative, irreversible DNA damage. Employing laser flash photolysis transient absorption spectroscopic techniques, we investigated the characteristics of electron transfer reactions in aqueous solutions between the 2'- deoxynucleoside 5'-monophosphates, dGMP, dAMP, dCMP and dTMP and a representative one-electron oxidant. The latter was a radical cation of a pyrene derivative with enhanced water-solubility, 7,8,9,10- tetrahydroxytetrahydrobenzo[a]pyrene (BPT). The BPT radical cation BPT+, was generated by intense nanosecond laser pulse (308 or 355 nm, 50-70 mJ pulse- 1 cm-2) by a non-linear consecutive two-photon absorption process. No electron transfer reactions were observed with dAMP, dTMP and dCMP, consistent with their unfavorable redox potentials. However, BPT+ efficiently oxidized dGMP with a rate constant k(b) = 1.7 ± 0.1) x 109 M- 1 s-1, which is smaller than the diffusion-controlled value by a factor of only ~ 3. The dGMP(-H) neutral radicals formed on time scales of a few microseconds, were identified by their characteristic transient absorption spectrum (λ(max) ~ 310 mn). The rate constant of electron transfer from dGMP to BPT+ was smaller in D2O by a factor of ~ 1.5 than in H2O. This kinetic isotope effect indicates that the electron transfer reaction from dGMP to BPT+ is accompanied by the deprotonation of dGMP+, and therefore appears to be a proton-coupled electron transfer reaction.
Fluorinated alcohol mediated displacement of the C10 acetoxy group of benzo[a]pyrene-7,8,9,10-tetrahydrotetraol tetraacetates: A new route to diol epoxide-deoxyguanosine adducts
Yagi, Haruhiko,Jerina, Donald M.
, p. 9983 - 9990 (2008/03/28)
(Chemical Equation Presented) We describe a novel trifluoroethanol (TFE) or hexafluoropropan-2-ol (HFP) mediated substitution reaction of the bay-region C10 acetoxy group in four stereoisomeric 7,8,9,10-tetraacetoxy-7,8,9, 10-tetrahydrobenzo[a]pyrenes (tetraol tetraacetates, two pairs of cis and trans isomers at the 9,10 positions) by the exocyclic N2-amino group of O6-allyl-3′,5′-di-O-(tert-butyldimethylsilyl)-2′- deoxyguanosine (3). The tetraacetates are derived from cis and trans hydrolysis of (±)-7β,8α-dihydroxy-9β,10β-epoxy-7,8,9,10- tetrahydrobenzo[a]pyrene (B[a]P DE-1) and of (±)-7β,8α- dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (B[a]P DE-2) at C-10 followed by acetylation. Excellent yields and high regioselectivity were observed. Similar cis/trans product ratios were observed for each set of cis and trans tetraol tetraacetates derived from DE-1 (～75/25) and from DE-2 (～67/33) in HFP. This strongly suggests that the substitution proceeds via an SN1 mechanism involving a carbocation intermediate that is common to the cis and trans tetraacetates. Since it is likely that the cis and trans products from 3 arise from different conformations of the carbocation, its lifetime must be sufficiently long to permit conformational equilibration before its capture by the purine nucleophile. The corresponding reaction of (±)-9α-bromo-7β,8α,10β- triacetoxy-7,8,9,10-tetrahydrobenzo[a]pyrene with 3 in HFP was highly regio- and stereoselective and gave exclusively trans 10β-adducts. This newly developed substitution reaction provides an attractive alternative synthetic strategy for the preparation of polycyclic hydrocarbon adducted oligonucleotide building blocks.
Chloride ion catalyzed conformational inversion of carbocation intermediates in the hydrolysis of a benzo[a]pyrene 7,8-diol 9,10-epoxide
Doan, Lanxuan,Yagi, Haruhiko,Jerina, Donald M.,Whalen, Dale L.
, p. 14382 - 14387 (2007/10/03)
A highly efficient procedure for converting 7β,8α-dihydroxy-9α,10α-epoxy-7,8,9, 10-tetrahydrobenzo[a]pyrene (1) to its trans-9,10-chlorohydrin (5) with excellent yield and purity by the reaction of anhydrous HCI in THF has been developed. The rate of reac
Nitrogen dioxide as an oxidizing agent of 8-oxo-7,8-dihydro-2′-deoxyguanosine but not of 2′-deoxyguanosine
Shafirovich,Cadet,Gasparutto,Dourandin,Geacintov
, p. 233 - 241 (2007/10/03)
The redox reactions of guanine and its widely studied oxidation product, the 8-oxo-7,8-dihydro derivative, are of significant importance for understanding the mechanisms of oxidative damage in DNA. Employing 2′-deoxyguanosine 5′-monophosphate (dGMP) and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG) in neutral aqueous solutions as model systems, we have used nanosecond laser flash photolysis to demonstrate that neutral radicals, dGMP(-H)?, derived by the one-electron oxidation and deprotonation of dGMP, can oxidize nitrite anions (NO2-) to the nitrogen dioxide radical ?NO2. In turn, we show that ?NO2 can give rise to a one-electron oxidation of 8-oxo-G, but not of dGMP. The one-electron oxidation of dGMP was initiated by a radical cation generated by the laser pulse-induced photoionization of a pyrene derivative with enhanced water solubility, 7,8,9,10-tetrahydroxytetrahydrobenzo[α]pyrene (BPT). The dGMP(-H)? neutral radicals formed via deprotonation of the dGMP?+ radical cations and identified by their characteristic transient absorption spectrum (λmax ～ 310 nm) oxidize nitrite anions with a rate constant of(2.6 ± 0.3) × 106 M-1 s-1. The 8-oxo-dG is oxidized by ?NO2 with a rate constant of (5.3 ± 0.5) × 106 M-1 s-1. The 8-oxo-dG(-H)? neutral radicals thus generated are clearly identified by their characteristic transient absorption spectra (λmax ～ 320 nm). The rate constant of 8-oxo-dG oxidation (k12) by the ?NO2 one-electron oxidant (the ?NO2/NO2- redox potential, E° ≈ 1.04 V vs NHE) is lower than k12 for a series of oxidizing aromatic radical cations with known redox potentials. The k12 values for 8-oxo-dG oxidation by different aromatic radical cations derived from the photoionization of their parent compounds depend on the redox potentials of the latter, which were in the range of 0.8-1.6 V versus NHE. The magnitude of k12 gradually decreases from a value of 2.2 × 109 M-1 s-1 (E° = 1.62 V) to 5.8 × 108 M-1 s-1 (E° = 1.13 V) and eventually to 5 × 107 M-1 s-1 (E° = 0.91 V). The implications of these results, including the possibility that the redox cycling of the ?NO2/NO2- species can be involved in the further oxidative damage of 8-oxo-dG in DNA in cellular environments, are discussed.
New insights on the mechanisms of the pH-independent reactions of benzo[a]pyrene 7,8-diol 9,10-epoxides
Doan,Bin,Yagi,Jerina,Whalen
, p. 6785 - 6791 (2007/10/03)
The rates and products of the reactions of (±)-7β,8α-dihydroxy-9β,10β-epoxy-7,8,9, 10-tetrahydrobenzo[α]pyrene alpyrene (1) and (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9, 10-tetrahydrobenzo[α]pyrene (2) in water and dioxane-water mixtures have been determined over a pH range wider than that of earlier studies. This study provides additional insight on the mechanisms of the pH-independent reactions of 1 and 2. The rate profile for reaction of 1 shows acid-catalyzed hydrolysis at pH 11.5. The rate decrease between pH 10 and pH 11.5 is accompanied by a decrease in the yield of tetrols from 60% (pH 8) to 29% (pH 11.2) and is interpreted to be the result of a partial change in mechanism brought about by attack of hydroxide ion acting as a base to deprotonate a carbocation intermediate and regenerate 1 at pH + and HO-, respectively. The lack of a rate depression at pH 10 and the product studies for the reaction of 2 in dilute sodium azide solutions suggest that the tetrol-forming reactions of the pH-independent reaction of 2 are concerted or near-concerted.
Halide effects in the hydrolysis reactions of (±)-7β,8α-dihydroxy- 9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo-[α]pyrene
Lin, Bin,Doan, Lanxuan,Yagi, Haruhiko,Jerina, Donald M.,Whalen, Dale L.
, p. 630 - 638 (2007/10/03)
Rates of reaction of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[α]pyrene (DE-2) have been determined in 1:9 dioxane-water solutions containing 1.0 M KC1, 0.5 M KBr, and 0.1 M NaI over the pH range 4- 13. These pH-rate profiles are more complicated than those for reaction of DE-2 in 0.2 M NaC1O4 solutions and are interpreted in part by mechanisms in which halide ion attacks the diol epoxide as a nucleophile at intermediate pH, resulting in the formation of a trans-halohydrin. Reaction of DE-2 in these halide solutions at pH - , 0.5 M Br-, and 0.1 M I- on DE-2 are the principal reactions in the pH range ca. 6-9, leading to intermediate trans-halohydrins that hydrolyze to tetrols. At pH ca. 9-11, halohydrin formed from attack of halide ion on DE-2 reverts back to epoxide, leading to a negative break in the pH-rate profile. The main product-forming reaction of DE-2 at pH 11.3 is the spontaneous reaction. At pH > 12, the rate of reaction of DE-2 increases due to a second- order reaction of HO- with DE-2.
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.
Photoemission probes of catalysis of benzo[a]pyrene epoxide reactions in complexes with linear, double-stranded and closed-circular, single-stranded DNA
Huang, Chao-Ran,Milliman, Ann,Price, Harry L.,Urano, Shigeyuki,Fetzer, Sharon M.,LeBreton, Pierre R.
, p. 7794 - 7805 (2007/10/02)
Fluorescence intensity measurements of overall, pseudo-first-order rate constants for two epoxide-containing metabolites of benzo[a]pyrene (BP) were carried out in Tris, EDTA buffer (pH 7.3) without DNA, and in buffer with double-stranded calf thymus DNA (DS ctDNA) and with closed-circular, single-stranded viral M13mp19 DNA (SS M13 DNA). Highly purified SS M13 DNA was employed in order to avoid polymeric contamination which is present in DNA samples obtained using a standard preparation method relying on phenol extraction and which influences results from measurements of DNA-ligand interactions. The BP metabolites examined were highly carcinogenic (±)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[e]pyrene (BPDE) and less genotoxic benzo[a]pyrene 4,5-oxide (BPO). Without DNA, BPDE hydrolyzes to 7,8,9,10-tetrahydroxytetrahydro-BP, while BPO hydrolyzes to trans-4,5-dihydroxy-4,5-dihydro-BP (BP45D) and rearranges to 4-hydroxy-BP. With DNA, BPDE and BPO hydrolysis and rearrangement are catalyzed, and DNA modification occurs. In DS ctDNA, previous kinetic and binding measurements indicate that catalysis occurs primarily at intercalation sites. In SS M13 DNA (0.20 mM), BPDE has overall, pseudo-first-order rate constants (k) of (12 ± 1) × 10-3 and (2.8 ± 0.5) × 10-3 s-1, at Na+ concentrations of 2.0 and 100 mM, respectively. At these Na+ concentrations, values of k measured in SS M13 DNA are 3-16 times larger than values measured without DNA, but smaller than values measured in DS ctDNA. For BPO, the ordering of k values without DNA, with SS M13 DNA, and with DS ctDNA is the same as for BPDE. At 2.0 mM Na+, the nonreactive diols, trans-7,8-dihydroxy-7,8-dihydro-BP (BP78D) and BP45D, which are model compounds for BPDE and BPO, respectively, have SS M13 DNA association constants [(7.2 ± 0.5) × 103 and (2.7 ± 0.5) × 103 M-1] that are 2.3 times smaller than DS ctDNA association constants. In contrast, at 100 mM Na+, association constants for SS M13 DNA are 2.9-3.1 times larger than for DS ctDNA. Fluorescence lifetime measurements indicate that, in SS M13 DNA, reversible binding involves intercalation into local duplex regions. Estimated catalytic rate constants (kcat) for BPDE hydrolysis in SS M13 DNA, obtained from BP78D association constants and from k values measured with and without DNA, are (22.8 ± 2.5) × 10-3 and (3.5 ± 0.7) × 10-3 s-1, at 2.0 and 100 mM Na+, respectively. For this Na+ concentration range, the ratio of kcat values for DS ctDNA versus SS M13 DNA is almost constant (1.7 ± 0.6) even though the absolute kcat values vary by more than a factor of 5. The similar magnitudes of kcat values for SS M13 DNA and DS ctDNA provide evidence that catalytic sites in SS M13 DNA are similar to intercalated catalytic sites in DS ctDNA.
Photoemission probes of hydrocarbon-DNA interactions: A comparison of DNA influences on the reactivities of (±)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene, benzo[a]pyrene 4,5-oxide, and benz[a]anthracene 5,6-oxide
Urano, Shigeyuki,Price, Harry L.,Fetzer, Sharon M.,Briedis, Anita V.,Milliman, Ann,LeBreton, Pierre R.
, p. 3881 - 3893 (2007/10/02)
Time-resolved fluorescence and UV photoelectron measurements have been employed to examine the influence of calf thymus DNA on the reactivities of epoxides derived from benzo[a]pyrene (BP) and benz[a]anthracene (BA). By monitoring the increase in fluorescence intensity, which accompanies reaction at 23°C, overall, pseudo-first-order rate constants have been measured for reactions of the highly carcinogenic bay region epoxide (±)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) and of two less carcinogenic K region epoxides benzo[a]pyrene 4,5-oxide (BPO) and benz[a]anthracene 5,6-oxide (BAO). Overall rate constants for hydrolysis and rearrangement reactions have been measured for BPDE, BPO, and BAO in buffer alone (1.0 mM sodium cacodylate, pH 7.1). The rate constants increase in the order BPO ((3.8 ± 0.1) × 10-6 s-1) -5 s-1) -4 s-1). These results have been compared with overall rate constants for reactions, carried out in calf thymus DNA, which result in catalyzed hydrolysis and rearrangement, as well as DNA adduct formation. In DNA, the ordering of the rate constants for BPO and BAO changes from that observed in buffer alone. The rate constants increase in the order BAO ((2.8 ± 0.1) × 10-3 s-1) -2 s-1) -1 s-1). This ordering is the same as the ordering of association constants for the reversible binding to DNA of the fluorescent diols trans-7,8-dihydroxy-7,8-dihydro-BP (BP78D), trans-4,5-dihydroxy-4,5-dihydro-BP (BP45D) and cis-5,6-dihydroxy-5,6-dihydro-BA (BAD), which are model compounds of BPDE, BPO, and BAO, respectively. For the model compounds, the association constants for intercalation increase in the order BAD ((3.6 ± 0.9(× 102 M-1) 3 M-1) 4 M-1). This ordering is consistent with the ordering of the association constants of BPDE ((2.5 ± 0.3) × 104 M-1) and of BPO ((6.0 ± 1.0) × 103 M-1). The temperature dependence of the association constants of the model compounds demonstrates that, for the intercalation of the BP diols into DNA, differences in the enthalpy of binding contribute significantly to differences in the free energy of binding. UV photoelectron data and results from ab initio molecular orbital calculations on BPDE, BPO, and BAO indicate that, for these three epoxides, the association constants increase as the ionization potentials decrease and the polarizabilities increase. The percentage of epoxide reaction that yields DNA adducts has been compared under varying conditions. For long reaction times (>1 h) in systems containing native, calf thymus DNA at low salt concentrations, the ordering of adduct yields is BPO (14.9 ± 1.1%) > BPDE (10.1 ± 3.0%) > BAO (3.6 ± 0.4%). For short reaction times (10 min) in systems containing native DNA stabilized with 0.10 mM Mg2+, the ordering of adduct yields is BPDE (7.3 ± 1.9%) > BPO (1.3 ± 0.1%) > BAO (0.1 ± 0.1%). These results suggest that the ability of an epoxide to form adducts with exposed DNA during long reaction times is less indicative of the genotoxic potency of the epoxide than its ability to form adducts with stabilized DNA during short reaction times.
