The perchloratoiron(III) complexes of a series of 2,6-disubstituted tetraphenylporphyrin ligands, where the 2,6-phenyl substituents were -H, -F, -Cl, -Br, or -OMe, as well as two 2,4,6-phenyl-substituted complexes, where the substituents were -Me and -OMe, have been investigated as a function of temperature by 1H NMR spectroscopy. Curvature in the 1/T dependence was evident in most cases. Forced linear extrapolation of the temperature dependence observed over the range of the study yielded Curie plots that include negative slopes with very large positive 1/T intercepts (Cl approximately Br > Me > H) to negative slope with near zero intercept (tri-OMe) to positive slope with very large negative intercept (F, di-OMe). The NMR results were combined with EPR spectroscopic data and curve-fitting procedures based on an expanded Curie law to arrive at a consistent overview of the variety of temperature-dependence behaviors observed. This overview relies upon the premise that, in addition to the ground state observed by EPR spectroscopy, one (or more) thermally accessible excited state(s) are populated to varying degrees over the temperature range of the NMR measurements. If only one excited state is considered, the analysis is consistent with the ground state being a largely intermediate-spin state (S = 3/2) for the majority of the complexes but a largely high-spin state (S = 5/2) for ((2,6-F2)4TPP)FeOClO3 and ((2,6-(OMe)2)4TPP)FeOClO3.

A possible role for metabolic activation of 2,2',5, 5'-tetrachlorobiphenyl (TCB) to quinonoid metabolites was investigated in vitro in rat liver microsomes and in vivo in male Sprague-Dawley rats. Incubation of TCB with phenobarbital-induced rat liver microsomes resulted in metabolism of TCB to 3-hydroxy-TCB (3-OH-TCB) and 3,4-dihydroxy-TCB (3,4-diOH-TCB), which were further oxidized to form a reactive intermediate that bound to liver proteins. The predominant species observed in the Raney nickel assay for cysteinyl adducts was identified as 3,4-diOH-TCB, consistent with an adduct having the structure 5-cysteinyl-3,6-dichloro-4-(2', 5'-dichlorophenyl)-1,2-benzoquinone. This adduct may arise via the Michael addition of the sulfhydryl group of cysteine to 3, 6-dichloro-4-(2',5'-dichlorophenyl)-1,2-benzoquinone (Cl(4)PhBQ). Metabolism of 3-OH-TCB by phenobarbital-induced microsomes in the presence of either NADPH or cumene hydroperoxide as a cofactor resulted in the formation of adducts. Dose-dependent formation of cysteinyl adducts was observed in liver cytosolic protein from rats treated with a single dose of TCB (0-200 mg/kg) by gavage. By regression analysis, the TCB adducts decayed with a half-life of 2. 03 +/- 0.131 days (mean +/- SE), which is approximately 2.5-fold shorter than the endogenous half-life for liver cytosolic protein in rat liver, suggesting adduct instability. Saturable formation of TCB adducts was observed in liver cytosolic protein of rats receiving multiple doses of TCB over 5 days. The levels of Cl(4)PhBQ-derived adducts were 2.1-fold greater than the estimated steady-state levels predicted by the single-dose treatment [97.7 +/- 13.2 vs 45.7 +/- 3. 73 (pmol/g)/(mg/kg of body weight)], suggesting induction of metabolism. A single cysteinyl adduct, inferred to be 5-cysteinyl-3, 6-dichloro-4-(2',5'-dichlorophenyl)-1,2-benzoquinone, was detected in brain cytosolic protein of rats treated with multiple doses of TCB with levels of 15.2 (pmol/g)/(mg/kg of body weight). Implied involvement of a reactive quinone in the liver and brain of TCB-treated rats supports the idea that quinonoid metabolites may be important contributors to PCB-derived oxidative damage to genomic DNA.

Fluoranthene is one of the predominant compounds found in soils and sediments contaminated with polycyclic aromatic hydrocarbons (PAH). Four bacterial strains isolated from PAH-contaminated soils transformed fluoranthene to a number of products during growth on phenanthrene, including the novel metabolites fluoranthene-2,3-dione (F23Q) and fluoranthene-1,5-dione (F15Q). Given the known toxicity and mutagenicity of F23Q, we focused on characterizing this metabolite with respect to its effects on the metabolism of other PAH. The yield of F23Q from fluoranthene ranged from 2% for Sphingomonas yanoikuyae R1 to greater than 20% for Pseudomonas stutzeri P16 and Bacillus cereus P21. None of the strains appeared capable of metabolizing F23Q any further. F23Q strongly inhibited phenanthrene removal by strain R1 but had a negligible to minor effect on phenanthrene degradation by the other organisms. At a concentration of 6.8 microM, F23Q also substantially inhibited the mineralization of benz[a]anthracene, benzo[a]pyrene (BaP), and chrysene by strain R1 as well as BaP mineralization by Pseudomonas saccharophila P15. Inhibition of BaP mineralization by strain P15 was still evident at an F23Q concentration of 0.68 microM. The inhibition of strain R1 by F23Q was explained in part by a cytotoxic effect, but results with strain P15 indicate that other mechanisms of inhibition occur. These findings suggest that quinones such as F23Q and F15Q have the potential to accumulate in PAH-contaminated systems and can inhibit the degradation of other PAH.

A fast, highly specific analytical method was developed to quantify 1,N6-ethenoadenine (epsilonA) in urine of rats. epsilonA is a highly mutagenic DNA adduct generated by vinyl chloride (VC) exposures as well as endogenously from lipid peroxidation. epsilonA was concentrated through extraction from rat urine by immunoaffinity chromatography and quantitated by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The average epsilonA recovery by immunoaffinity extraction was 66%. The LC/ESI-MS selected-ion monitoring (SIM) of the response ratio of epsilonA to its isotopically labeled internal standard [15N5]epsilonA was linear (r2 = 0.999) and reproducible from 0.15 to 30 pmol/injection. The detection limit obtained in the routine analysis of urine of unexposed rats was 270 fmol/sample with a signal-to-noise ratio (S/N) 3:1. The concentration of endogenous epsilonA was determined to be 21.6 +/- 14.8 pmol/mL (3 rats). Following portal injection of chloroethylene oxide (CEO; the putative active metabolite of VC), the rate of epsilonA excretion in urine was greatest from 0 to 24 h, with approximately 90% of the CEO-induced epsilonA excreted. By 132 h, the excretion of epsilonA was similar to pretreatment amounts. The accuracy of the quantitation was 107 +/- 6% (n = 4), established by analyzing urine of an unexposed rat spiked with authentic epsilonA. These data indicate that the LC/ESI-MS with immunoaffinity extraction method is precise and accurate for epsilonA quantification. The measurement of epsilonA in urine provides a potential biomarker for exposure to chemicals and processes that form this adduct.