Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized 'essential climate variable' ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

Carboxylate and salicylic OH coordinate bonding as well as intramolecular and intermolecular hydrogen bonding of bis-3,5-diisopropylsalicylatozinc(II), [Zn-II(3,5-DIPS)(2)], with Lewis bases were studied to determine mechanisms accounting for antioxidant reactivity of Zn-II(3,5-DIPS)(2). Apparent thermodynamic parameters: K-cq, Delta S-0, Delta H-0, and Delta G(0) were determined for these equilibria with bonding of two molecules of dimethyl sulfoxide-d(6) (DMSO) or ethyl acetate-d(8) (EA) to the Zn-II using NMR and FTIR. We conclude that addition of two equivalents of DMSO or EA to non-polar solutions of Zn-II(3,5-DIPS)(2) results in bonding of DMSO or EA to Zn-II via sulfoxide or ester carbonyl oxygen atoms with ternary complex formation, leading to weakening of carboxylate and salicylic OH coordinate bonding to Zn-II and strengthening intramolecular hydrogen bonding between protons of salicylic OH groups and carboxylate oxygens. Subsequent addition of two or three additional equivalents of DMSO or EA leads to intermolecular hydrogen bonding between protons of salicylic OH groups.

The polycyclic nitroaromatic hydrocarbon 1-nitropyrene is an environmental pollutant, a potent bacterial mutagen, and a car cinogen. Xanthine oxidase, a mammalian nitroreductase, cata lyzed the in vitro metabolic activation of this compound to DNAbound adducts. Maximum adduct formation occurred at pH 5.5 to 6.0 and was increased by the addition of catatase to the incubation medium. DMA binding from 1-nitropyrene was inhib ited by hydrogen peroxide, L-ascorbate, and glutathione. Enzy matic hydrolysis of the modified DMA and subsequent analysis by high-pressure liquid chromatography indicated the presence of one major and two minor adducts. The major adduct was characterized by mass spectrometry and nuclear magnetic res onance spectroscopy as A/-(deoxyguanosin-8-yl)-1-aminopyrene. The minor adducts appear to be decomposition products of the major adduct. When Salmonella typhimurium TA1538 was incu bated with 1-nitropyrene, a strong correlation was found be tween the extent of DMA binding and the frequency of induced histidine reversions. Analysis of the bacterial DMA indicated one major adduct which had Chromatographie properties and pK«s identical to those of A/-(deoxyguanosin-8-yl)-1-aminopyrene. These data indicate that N-hydroxy-1-aminopyrene is probably the mutagenic and DMA-binding species formed during the met abolic reduction of 1-nitropyrene.

2-Nitropyrene, the geometric isomer of the most studied nitropolycyclic aromatic hydrocarbon (nitro-PAH), 1-nitropyrene, is an environmental contaminant detected in ambient air and a potent direct-acting mutagen. Its metabolic activation leading to the formation of DNA adducts was studied. The activated metabolite, W-hydroxy-l-aminopyrene, was prepared and reacted with calf thymus DNA. Upon enzymatic hydrolysis of the DNA, the resulting nucleosides were separated by HPLC, and the adducts were characterized by mass and proton NMR spectral analysis. Both AKdeoxyguanosin-8-yl)-2-aminopyrene and iV-(deoxyadenosin-8yl)-2-aminopyrene, in a 5:2 ratio, were identified. These adducts were then utilized as standards to identify the DNA adducts formed from reaction of [H]2-nitropyrene with DNA mediated by liver microsomes and cytosols of mouse and rat. In all cases, both adducts were formed. The quantities of the two adducts formed in each system were: mouse liver microsomes (11.3 pmol [H]2-nitropyrene/mg DNA), rat liver microsomes (23), mouse liver cytosol (11.4) and rat liver cytosol (5.1). Thus, these adducts were formed in highest yield from rat liver microsomes and the lowest from rat liver cytosol. The deoxyguanosine/deoxyadenosine adduct ratio was higher from rat and mouse liver microsomes (7.8:9.2) than from rat and mouse liver cytosols (2.5:3.1). Our results represent the first direct demonstration of a C8-deoxyadenosine adduct being formed as a major product from the reaction of a nitro-PAH metabolite with DNA. 1 -Nitropyrene is the most abundant environmental nitro-PAH and its carcinogenic activity has been studied more closely than that of other nitro-PAHs (1 -7 , 10-13, 27-31). Thus, in connection with the study of structure—activity relationships, it is important to study its structural isomers, 2and 4-nitropyrene. 2-Nitropyrene has recently been found in ambient paniculate organic matter in quantities comparable to 1-nitropyrene (32,33). Unlike 1-nitropyrene, which is formed during combustion processes by nitration of pyrene via an ionic mechanism, 2-nitropyrene is formed via a free radical mechanism. This is thought to occur during source-receptor transport by atmospheric reactions of adsorbed or gas-phase pyrene with oxides of nitrogen, nitric acid and other related species (33). 2-Nitropyrene has been found to exhibit much higher direct-acting mutagenicity (2225-2569 revertants/nmol) than 1-nitropyrene ( -470 revertants/nmol) (1,4,34,35). Consequently, it is essential to study its metabolic activation and compare these results with those obtained with 1-nitropyrene. Its potent direct-acting mutagenicity implicates nitroreduction of 2-nitropyrene as an important metabolic activation pathway for mutation. In this study, we report the preparation of A-hydroxy-2-aminopyrene, its reaction with calf thymus DNA for the synthesis of DNA adducts, and utilization of these adducts as standards for the binding of 2-nitropyrene with DNA mediated with rat and mouse liver microsomes and cytosols. Two adducts, /V-(deoxyguanosin8-yl)-2-aminopyrene and A^-(deoxyadenosin-8-yl)-2-aminopyrene, are formed in substantial quantities in all four enzyme systems. Our results present the first direct example of the formation of a C8-deoxyadenosinyl adduct as a major product of the reaction of nitro-PAHs with DNA. Since the carcinogen-deoxyadenosine adducts have been suggested as being important for the genotoxic activity of nitro-PAHs (36,37), our findings may be valuable in the elucidation of the potent direct-acting mutagenicity of this compound.

Tattooing has become a popular recreational practice among younger adults over the past decade. Although some of the pigments used in tattooing have been described, very little is known concerning the toxicology, phototoxicology or photochemistry of these pigments. Seven yellow tattoo inks were obtained from commercial sources and their pigments extracted, identified and quantitatively analyzed. The monoazo compound Pigment Yellow 74 (PY74; CI 11741) was found to be the major pigment in several of the tattoo inks. Solutions of commercial PY74 in tetrahydrofuran (THF) were deoxygenated using argon gas, and the photochemical reaction products were determined after exposure to simulated solar light generated by a filtered 6.5 kW xenon arc lamp. Spectrophotometric and high-pressure liquid chromatography (HPLC) analyses indicated that PY74 photodecomposed to multiple products that were isolated using a combination of silica chromatography and reversed-phase HPLC. Three of the major photodecomposition products were identified by nuclear magnetic resonance and mass spectrometry as N-(2-methoxyphenyl)-3-oxobutanamide (o-acetoacetanisidide), 2-(hydroxyimine)-N-(2-methoxyphenyl)-3-oxobutanamide and N,N''-bis(2-methoxyphenyl)urea. These results demonstrate that PY74 is not photostable in THF and that photochemical lysis occurs at several sites in PY74 including the hydrazone and amide groups. The data also suggest that the use of PY74 in tattoo inks could potentially result in the formation of photolysis products, resulting in toxicity at the tattoo site after irradiation with sunlight or more intense light sources.

The environmental contaminants 1- and 3-nitrobenzo[a]pyrene (1- and 3-nitro-BaP) are mutagens in Chinese hamster ovary (CHO) cells with exogenous metabolic activation. Previous studies demonstrated the potent direct-acting mutagenicity of the oxidized metabolites, trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydro-1-nitrobenzo[a] pyrene (1-NBaPDE) and trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9, 10-tetrahydro-3-nitrobenzo[a]pyrene (3-NBaPDE), and the partially nitroreduced metabolites, 1- and 3-nitrosobenzo[a]pyrene (1- and 3-NO-BaP). In this study, we have identified the major adduct formed by incubation of calf thymus DNA with 1-NBaPDE and used this standard in conjunction with other adduct standards to characterize the 32P-postlabeled DNA adducts produced by 1- and 3-nitro-BaP metabolites in CHO cultures. The major adduct from 1-NBaPDE exposure was 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-1- nitrobenzo[a]pyrene; from 3-NBaPDE, 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-3- nitrobenzo[a]pyrene; from 1-NO-BaP, 6-(deoxyguanosin-N2-yl)-1-aminobenzo[a]pyrene; and from 3-NO-BaP, 6-(deoxyguanosin-N2-yl)-3-aminobenzo[a]pyrene. For comparison, the adducts formed by trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene and the related nitroreduced derivative 6-nitrosobenzo[a]pyrene were also examined. The nitrobenzo[a]pyrene DNA adducts described in this study are proposed to be involved in the mutagenicity of 1- and 3-nitro-BaP upon either oxidative or reductive metabolism.

Benzo[e]pyrene is a pentacyclic aromatic hydrocarbon, which, unlike its structural isomer benzo[a]pyrene, is not a potent carcinogen or mutagen. The metabolism of benzo[e]pyrene was studied using the filamentous fungus Cunninghamella elegans ATCC 36112. C. elegans metabolized 65% of the [9, 10, 11, 12-3H]benzo[e]pyrene and unlabeled benzo[e]pyrene added to Sabouraud dextrose broth cultures after 120 h of incubation. Three major metabolites of benzo[e]pyrene were separated by reversed-phase high-performance liquid chromatography. These metabolites were identified by 1H and 13C NMR, UV-visible, and mass spectral analyses as 3-benzo[e]pyrenylsulfate, 10-hydroxy-3-benzo[e]pyrenyl sulfate, and benzo[e]pyrene 3-O-β-glucopyranoside.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are direct-acting mutagens and carcinogens that are considered a risk to human health. We investigated the metabolism of 2-nitrofluorene by the fungus Cunninghamella elegans ATCC 36112. At 144 h of incubation, C. elegans had metabolized about 81% of the [9-14C]-2-nitrofluorene, resulting in 6 metabolites. The major metabolites were separated by reversed-phase high-performance liquid chromatography and identified by 1H NMR, ultraviolet (UV)-visible, and mass spectral analyses as 2-nitro-9-fluorenol, 2-nitro-9-fluorenone, 6-hydroxy-2-nitrofluorene, and sulfate conjugates of 7-hydroxy-2-nitro-9-fluorenone and 7-hydroxy-2-nitrofluorene. 2-Nitro-9-fluorenol accounted for about 62% of the total metabolism. For comparison with the microbial system, experiments with liver microsomes of rats pretreated with 3-methyl-cholanthrene were conducted. Microsomal incubations indicated formation of phenolic and ring-hydroxylated products of 2-nitrofluorene. 2-Nitrofluorene and hydroxylated metabolites have been previously implicated as direct-acting mutagens in bacterial assays and have shown sister chromatid exchanges in vivo in bone marrow cells and in vitro in ovary cells and unscheduled DNA synthesis in mammalian studies. Previous studies with other PAHs using C. elegans have shown that the phenols and glucoside and sulfate conjugates of phenols are generally less mutagenic than the parent. The results from the metabolism of 2-nitrofluorene by C. elegans suggests the detoxification potential of this fungus.

The fungus, Cunninghamella elegans, was used as a microbial model of mammalian drug metabolism to biotransform a tricyclic antidepressant, cyclobenzaprine. Seventy-five percent of this drug at a concentration of 1 mM was metabolized within 72 h by C. elegans grown on Sabouraud dextrose broth. Milligram amounts of fungal metabolites were isolated by reversed-phase high performance liquid chromatography (HPLC) and their structures were characterized by 1H NMR spectroscopy, mass spectrometry, and UV spectroscopy analyses. The major fungal metabolites of cyclobenzaprine were 2-hydroxycyclobenzaprine (59%), N-desmethylcyclobenzaprine (21%), cyclobenzaprine trans-10,11-dihydrodiol (5%), N-desmethyl-2-hydroxy-cyclobenzaprine (3%), 3-hydroxycyclobenzaprine (3%), and cyclobenzaprine N-oxide (1%). These fungal metabolites were used as standards to investigate the metabolism of cyclobenzaprine by rat liver microsomes. Rat liver microsomes also biotransformed cyclobenzaprine to produce similar metabolites as the fungus. The isotope labeling of 2-hydroxycyclobenzaprine by 18O2 and the trans-configuration of the dihydrodiol suggested that these reactions were catalyzed by cytochrome P-450 monooxygenases in C. elegans. These results also demonstrated that the fungal biotransformation system could be used to predict and synthesize the mammalian drug metabolites.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and persistent environmental pollutants; some are mutagenic, toxic, and carcinogenic and remain a public health concern. We investigated the metabolism of mixtures of PAHs and a tetracyclic aromatic hydrocarbon, chrysene, by the filamentous fungus, Cunninghamella elegans ATCC 36112. Cunninghamella elegans metabolized a mixture of PAHs including the carcinogen benzo[a]pyrene, phenanthrene, fluoranthene, pyrene, and acenaphthene completely to hydroxylated intermediates within 24 h. The metabolites from the PAH mixtures were similar to those formed in earlier studies of individual PAH compounds. In separate experiments with chrysene, C. elegans metabolized about 45% of the [5,6,11,12-14C]chrysene added to cultures during 144 h incubation. The two major metabolites of chrysene were separated by reverse-phase high performance liquid chromatography and identified by ultraviolet–visible, mass spectral, and1H-nuclear magnetic resonance techniques as sulfate conjugates of 2,8-dihydroxychrysene and 2-hydroxychrysene. The two major metabolites accounted for about 33% of the total metabolism. The formation of sulfate conjugates of phenolic chrysene metabolites and glucoside conjugates and hydroxylated products of PAH mixtures by C. elegans may be a detoxification step, because these types of products are generally less toxic than the parent compound. Key words: polycyclic aromatic hydrocarbons, PAH mixtures, chrysene, Cunninghamella elegans, biotransformation, oxidation.

1-Nitropyrene, the most abundant nitro-polycyclic aromatic hydrocarbon in the environment, is a known mammalian and bacterial mutagen and a tumorigen in animals. Early studies on DNA adduct characterization for 1-nitropyrene identified N-(deoxyguanosin-8-yl)-1-aminopyrene as the major product from the modification of calf thymus DNA with N-hydroxy-1-aminopyrene, the activated metabolite from nitroreduction of 1-nitropyrene. In this paper, we report the identification of two N2-deoxyguanosinyl adducts, in addition to N-(deoxyguanosin-8-yl)-1-aminopyrene, formed from the reaction of N-hydroxy-1-aminopyrene, prepared in situ, with calf thymus DNA. These DNA adducts were identified as 6-(deoxyguanosin-N2-yl)-1-aminopyrene and 8-(deoxyguanosin-N2-yl)-1-aminopyrene. The two N2-deoxyguanosinyl adducts were also identified in an ascorbic acid-catalyzed activation of 1-nitrosopyrene and in the mammary gland of female Sprague-Dawley rats administered 1-nitropyrene. The DNA adducts were also formed when 1-nitropyrene was metabolized by xanthine oxidase in the presence of calf thymus DNA, and when 1-nitropyrene was activated by rat liver microsomes and cytosols, as well as from DNA isolated from Salmonella typhimurium suspension cultures incubated with 1-nitropyrene.

A fungal biotransformation system as an in vitro model for mammalian drug metabolism was investigated. Amitriptyline, a widely used antidepressant, was effectively biotransformed within 72 hr by the filamentous fungus, Cunninghamella elegans. Eight major metabolites in HPLC elution order (11-hydroxyamitriptyline N-oxide, 11-hydroxynortriptyline, 11-hydroxyamitriptyline, 10-hydroxyamitriptyline, 3-hydroxyamitriptyline, 2-hydroxyamitriptyline, nortriptyline, and amitriptyline N-oxide) were produced at estimated molar ratios of 2:1:10:0.6:0.1:1.2.5:0.5, respectively. These metabolites were isolated by HPLC and identified by UV/MS analyses, as well as NMR spectroscopic analysis for most of these metabolites. In some cases, they were also compared with authentic standards. Glucose, culture age, and substrate concentration significantly affected the extent of amitriptyline metabolism. Kinetic studies indicated that nortriptyline and 11-hydroxyamitriptyline were produced as initial major metabolites. The hydroxylated metabolite was excreted from mycelia, but amitriptyline and its N-demethylated metabolite, nortriptyline, were not. An 18O2 labeling experiment showed that the oxygen atoms in 11-hydroxyamitriptyline and 2-hydroxyamitriptyline were derived from molecular oxygen. The cytochrome P450 inhibitors SKF 525-A (1.5 mM), metyrapone (2.0 mM), and 1-aminobenzotriazole (1.0 mM) inhibited the biotransformations of amitriptyline by 50, 75, and 95%, respectively. A microsomal preparation was shown to catalyze the 11-hydroxylation of amitriptyline, which was inhibited by SKF 525-A and carbon monoxide. The similarities of amitriptyline metabolism in C. elegans and in humans and rats are discussed.

1-Nitropyrene, the most abundant nitro-polycyclic aromatic hydrocarbon in the environment, is a known mammalian and bacterial mutagen and a tumorigen in animals. Early studies on DNA adduct characterization for 1-nitropyrene identified N-(deoxyguanosin-8-y1)-1-aminopyrene as the major product from the modification of calf thymus DNA with N-hydroxy-1-aminopyrene, the activated metabolite from nitroreduction of l-nitropyrene. In this paper, we report the identification of two N-2-deoxyguanosinyl adducts, in addition to N-(deoxyguanosin-8-y1)-1-aminopyrene, formed from the reaction of N-hydroxy-1-aminopyrene, prepared in situ, with calf thymus DNA. These DNA adducts were identified as 6-(deoxyguanosin-N-2-yl)-1-aminopyrene and 8-(deoxyguanosin-N-2-yl)-1-aminopyrene. The two N-2-deoxyguanosinyl adducts were also identified in an ascorbic acid-catalyzed activation of 1-nitrosopyrene and in the mammary gland of female Sprague-Dawley rats administered 1-nitropyrene. The DNA adducts were also formed when 1-nitropyrene was metabolized by xanthine oxidase in the presence of calf thymus DNA, and when 1-nitropyrene was activated by rat liver microsomes and cytosols, as well as from DNA isolated from Salmonella typhimurium suspension cultures incubated with 1-nitropyrene.

We recently reported that the reaction of N-hydroxy-3-aminobenzo[a] pyrene with calf thymus DNA produced 6-(deoxyguanosin-N2-yl)-3-aminobenzo[a]pyrene as the predominant adduct. The deoxyguanosinyl group of this adduct resides at the C6 position, which is remote from the reaction site, the nitrenium ion. It is significant to determine if formation of this type of DNA adduct is general and whether or not adduct formation is due to an increase in the stabilization of the nitrenium ion by increasing aromaticity. Thus, reduction of 1-nitro-7,8,9,10-tetrahydrobenzo[a]pyrene, 3-nitro-7,8,9,10-tetrahydrobenzo[a]pyrene, and 1-nitrobenzo[a]pyrene, both chemically and enzymatically, followed by reaction with calf thymus DNA was investigated. DNA was isolated and enzymatically digested, and the resulting modified nucleosides were separated by HPLC. Upon spectral analyses by mass and proton nuclear magnetic resonance spectroscopy, 6-(deoxyguanosin-N2-yl)-1-amino-7,8,9,10-tetrahydrobenzo[a] pyrene, 6-(deoxyguanosin-N2-yl)-3-amino-7,8,9,10-tetrahydrobenzo[a]pyrene, and 6-(deoxyguanosin-N2-yl)-1-aminobenzo[a]pyrene were identified, respectively. The same DNA adducts were formed from xanthine oxidase-mediated reductive metabolism of 1-nitro-7,8,9,10-tetrahydrobenzo[a]pyrene, 3-nitro-7,8,9,10-tetrahydrobenzo[a]pyrene, and 1-nitrobenzo[a]pyrene in the presence of calf thymus DNA. Thee results indicate that formation of N2-deoxyguanosinyl adducts of this type is common and that increasing the aromaticity by increasing the number of aromatic rings is not a decisive factor in directing their formation.

2-Nitrobenzo[a]pyrene (2-nitro-BaP) induced 100% liver tumor incidence in the neonatal mouse tumorigenicity assay and exhibited the highest mutagenicity among the 1-, 2-, 3-, and 6-nitro-BaP when tested in Salmonella typhimurium TA98 and TA100. To determine the metabolic activation pathways leading to tumor initiation and mutation induction, we have studied the aerobic metabolism of 2-nitro-BaP by Sprague-Dawley rat and B6C3F1 mouse liver microsomes. Metabolites were isolated by HPLC and characterized by spectral analyses, including UV-visible absorption, mass and proton NMR spectroscopy. With both rat and mouse liver microsomes, 2-nitro-BaP trans-9,10-dihydrodiol and 2-nitro-BaP trans-7,8-dihydrodiol were formed as the predominant metabolites, and 2-nitro-BaP 7,8,9,10-tetrahydrotetrol was produced in trace quantities. 2-Nitro-BaP and its two dihydrodiol metabolites were assayed in Salmonella typhimurium tester strain TA98. 2-Nitro-BaP trans-7,8-dihydrodiol, in the presence of S9, was the most mutagenic (6156±288 revertants/plate). The overall results suggest that ring-oxidation of 2-nitro-BaP to the bay-region diol-epoxide, 2-nitro-BaP trans-7,8-diol-anti-9,10-epoxide, is a principal metabolic activation pathway.

We investigated the metabolism of 3-nitrofluoranthene by filamentous fungus, Cunninghamella elegans ATCC 36112. Cunninghamella elegans metabolized about 72% of the 3-nitro[3,4-14C]fluoranthene added during 144 h of incubation to 2 major metabolites. These metabolites were separated by reversed-phase high-performance liquid chromatography and identified as 3-nitrofluoranthene-8-sulfate and 3-nitrofluoranthene-9-sulfate by 1H nuclear magnetic resonance, UV-visible, and mass spectral techniques. These results, in conjunction with previous studies on the fungal metabolism of fluoranthene, indicate that the nitro substituent at the C-3 position of fluoranthene sterically hinders epoxidation and shifts metabolism to the C-8 and C-9 positions. Since the phenolic microsomal metabolites of 3-nitrofluoranthene are mutagenic, the formation of sulfate conjugates of 8- and 9-hydroxy-3-nitrofluoranthene by C. elegans suggests that the fungal metabolic pathways may be beneficial for detoxification of this ubiquitous pollutant.

A metabolite of benzo[a]pyrene, 9-r,10-t-dihydroxy-7,8-c-oxy-7,8,9,10- tetrahydrobenzo[a]pyrene (BPDE-III), that is not thought to be involved in carcinogenesis has nevertheless been shown to bind extensively to DNA in vitro. The adducts formed by this non-bay-region diol epoxide in Chinese hamster ovary cells are much less mutagenic than those formed by an isomeric diol epoxide that is carcinogenic. We have isolated and characterized three major adducts formed by in vitro reaction of BPDE-III with DNA. The major adduct, accounting for over half of the total is formed by reaction of BPDE-III with the N7 position of dGuo and is recovered after enzymatic digestion as an N7-Gua adduct. A second major adduct involves the N2 position of dGuo, while the third adduct is tentatively identified as a C8-substituted dGuo. Little or no reaction with deoxyadenosine residues is detected. The N7 adduct is unstable in DNA at 37 degrees C and is released as the modified base with a half-life of about 24 h. This adduct lability apparently leads to single-strand breaks and alkali-sensitive sites in the DNA and may account in part for some of the biological properties of BPDE-III adducts. This represents the first description of an N7-dGuo adduct that is formed in DNA as the major adduct by a diol epoxide derived from a carcinogenic polycyclic aromatic hydrocarbon.

The structures of selected phenolic metabolites of 2- and 3-nitrofluoranthene have been analyzed. H-1 NMR spectral analysis at 500 MHz using one- and two-dimensional methods proves that the site of hydroxy substitution in two metabolites previously reported as 3-nitrofluoranthen-8-ol and 3-nitrofluoranthen-9-ol had been reversed. A third and previously unidentified metabolite is shown to be 3-nitrofluoranthen-7-ol. Complete analyis of NMR spectral data on 2- and 3-nitrofluoranthene enabled confirmation of the previously reported structures of 2-nitrofluoranthen-8-ol and 2-nitrofluoranthen-9-ol from derived chemical shift substituent effects. Chemical shift data suggest that the nitro group is not strictly coplanar with the aromatic ring system in solution and that metabolism at a distant site can alter the conformation about the C-N bond of the nitro group. Reported mutagenicity data are analyzed relative to imine quinone formation, chemical shift substituent effects, electronegativity effects, and conformation in an attempt to explain the large differences in mutagenicity between the C8 and C9 hydroxy isomers of 2- and 3-nitrofluoranthene.

Pure cultures of anaerobic intestinal bacteria and mixed fecal microflora from human, rat, mouse, and pig were screened for the ability to metabolize 7-nitrobenz[a]anthracene (7-NO2BA). Based on analysis by high-performance liquid chromatography (HPLC) and by ultraviolet (UV), mass, and nuclear magnetic resonance (NMR) spectral techniques, the compounds were identified as 7-aminobenz[a]anthracene (7-NH2BA) and benz[a]anthracene 7,12-dione (dione). Identification of 7-NH2BA as a metabolite of 7-NO2BA indicates that the anaerobic intestinal bacteria are capable of reducing 7-NO2BA to potentially bioactive intermediates. The reductive capacities of the mixed intestinal microflora were generally greater than those of pure cultures. Thus, metabolism of 7-NO2BA in the intestinal tract may be underestimated if pure cultures are used as the sole method for evaluating the potential hazard.