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1.  Communication: Synthesis of a Novel Triphenyltin(IV) Derivative of 2- Mercaptonicotinic Acid with Potent Cytotoxicity in vitro  
A novel triphenyltin(IV) derivative of 2-mercaptonicotinic acid (H2mna) of formula {[(C6H5)3Sn]2(mna).[(CH3)2CO]} (1) has been synthesized and characterized by elemental analysis and 1H, 13C-NMR, and FT-IR spectroscopic techniques. The crystal structure of complex (1) has been determined by single crystal X-ray diffraction analysis at 173(1) K. Compound (1) contains two triphenyltin moieties linked by a doubly de-protonated 2,mercaptonicotinic acid (H>2mna). It is an example of a pentacoordinated Ph3SnXY system with an axial-equatorial arrangement of the phenyl groups at Sn(1). Compound (1), exhibits potent, in vitro, cytotoxicity against sarcoma cancer cells (mesenchymal tissue) from the Wistar rat, polycyclic aromatic hydrocarbons (PAH, benzo[a]pyrene) carcinogenesis.
PMCID: PMC2267064  PMID: 18365056
2.  Bacillus subtilis is a Potential Degrader of Pyrene and Benzo[a]pyrene 
Polycyclic Aromatic Hydrocarbons (PAHs) are a group of compounds that pose many health threats to human and animal life. They occur in nature as a result of incomplete combustion of organic matter, as well as from many anthropogenic sources including cigarette smoke and automobile exhaust. PAHs have been reported to cause liver damage, red blood cell damage and a variety of cancers. Because of this, methods to reduce the amount of PAHs in the environment are continuously being sought. The purpose of this study was to find soil bacteria capable of degrading high molecular weight PAHs, such as pyrene (Pyr) and benzo[a]pyrene (BaP), which contain more than three benzene rings and so persist in the environment. Bacillus subtilis, identified by fatty acid methyl ester (FAME) analysis, was isolated from PAH contaminated soil. Because it grew in the presence of 33μg/ml each of pyrene, 1-AP and 1-HP, its biodegradation capabilities were assessed. It was found that after a four-day incubation period at 30°C in 20μg/ml pyrene or benzo[a]pyrene, B. subtilis was able to transform approximately 40% and 50% pyrene and benzo[a]pyrene, respectively. This is the first report implicating B. subtilis in PAH degradation. Whether or not the intermediates resulting from the transformation are more toxic than their parent compounds, and whether B. subtilis is capable of mineralizing pyrene or benzo[a]pyrene to carbon dioxide and water, remains to be evaluated.
PMCID: PMC3810630  PMID: 16705827
Polycyclic Aromatic Hydrocarbons; bioremediation; Bacillus subtilis
3.  Substrate Specificity and Structural Characteristics of the Novel Rieske Nonheme Iron Aromatic Ring-Hydroxylating Oxygenases NidAB and NidA3B3 from Mycobacterium vanbaalenii PYR-1 
mBio  2010;1(2):e00135-10.
The Rieske nonheme iron aromatic ring-hydroxylating oxygenases (RHOs) NidAB and NidA3B3 from Mycobacterium vanbaalenii PYR-1 have been implicated in the initial oxidation of high-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs), forming cis-dihydrodiols. To clarify how these two RHOs are functionally different with respect to the degradation of HMW PAHs, we investigated their substrate specificities to 13 representative aromatic substrates (toluene, m-xylene, phthalate, biphenyl, naphthalene, phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, benzo[a]pyrene, carbazole, and dibenzothiophene) by enzyme reconstitution studies of Escherichia coli. Both Nid systems were identified to be compatible with type V electron transport chain (ETC) components, consisting of a [3Fe-4S]-type ferredoxin and a glutathione reductase (GR)-type reductase. Metabolite profiles indicated that the Nid systems oxidize a wide range of aromatic hydrocarbon compounds, producing various isomeric dihydrodiol and phenolic compounds. NidAB and NidA3B3 showed the highest conversion rates for pyrene and fluoranthene, respectively, with high product regiospecificity, whereas other aromatic substrates were converted at relatively low regiospecificity. Structural characteristics of the active sites of the Nid systems were investigated and compared to those of other RHOs. The NidAB and NidA3B3 systems showed the largest substrate-binding pockets in the active sites, which satisfies spatial requirements for accepting HMW PAHs. Spatially conserved aromatic amino acids, Phe-Phe-Phe, in the substrate-binding pockets of the Nid systems appeared to play an important role in keeping aromatic substrates within the reactive distance from the iron atom, which allows each oxygen to attack the neighboring carbons.
Since the discovery of microbial ring-hydroxylating oxygenases (RHOs) in 1970, the sequences, structures, and enzyme biochemistry, including enantiospecific products, of RHOs have been studied and discussed extensively from the perspective of biodegradation, biotransformation, and biocatalysis processes. However, with all that effort to elucidate the enzymatic mechanisms of RHOs, little is known about the biochemistry and enzymology underlying high-molecular-weight (HMW) polycyclic aromatic hydrocarbon (PAH) degradation. We used Mycobacterium vanbaalenii PYR-1 Nid enzymes, the first type V RHO members to display an apparent substrate preference for HMW PAHs. Here, we examine the mechanism of the RHO reaction by integrating structural information of the NidAB and NidA3B3 enzymes with substrate and product data. This study gives us an understanding of how the model RHO systems of M. vanbaalenii PYR-1 metabolize HMW PAHs. The information obtained would also be helpful for successful application of RHO enzymes to the production of industrially and medically important chiral chemicals and the development of PAH bioremediation technologies.
PMCID: PMC2921158  PMID: 20714442
4.  Cloning and characterization of a 9-lipoxygenase gene induced by pathogen attack from Nicotiana benthamiana for biotechnological application 
BMC Biotechnology  2011;11:30.
Plant lipoxygenases (LOXs) have been proposed to form biologically active compounds both during normal developmental stages such as germination or growth as well as during responses to environmental stress such as wounding or pathogen attack. In our previous study, we found that enzyme activity of endogenous 9-LOX in Nicotiana benthamiana was highly induced by agroinfiltration using a tobacco mosaic virus (TMV) based vector system.
A LOX gene which is expressed after treatment of the viral vectors was isolated from Nicotiana benthamiana. As the encoded LOX has a high amino acid identity to other 9-LOX proteins, the gene was named as Nb-9-LOX. It was heterologously expressed in yeast cells and its enzymatic activity was characterized. The yeast cells expressed large quantities of stable 9-LOX (0.9 U ml-1 cell cultures) which can oxygenate linoleic acid resulting in high yields (18 μmol ml-1 cell cultures) of hydroperoxy fatty acid. The product specificity of Nb-9-LOX was examined by incubation of linoleic acid and Nb-9-LOX in combination with a 13-hydroperoxide lyase from watermelon (Cl-13-HPL) or a 9/13-hydroperoxide lyase from melon (Cm-9/13-HPL) and by LC-MS analysis. The result showed that Nb-9-LOX possesses both 9- and 13-LOX specificity, with high predominance for the 9-LOX function. The combination of recombinant Nb-9-LOX and recombinant Cm-9/13-HPL produced large amounts of C9-aldehydes (3.3 μmol mg-1 crude protein). The yield of C9-aldehydes from linoleic acid was 64%.
The yeast expressed Nb-9-LOX can be used to produce C9-aldehydes on a large scale in combination with a HPL gene with 9-HPL function, or to effectively produce 9-hydroxy-10(E),12(Z)-octadecadienoic acid in a biocatalytic process in combination with cysteine as a mild reducing agent.
PMCID: PMC3079629  PMID: 21450085
Lipoxygenase; hydroperoxide lyase; viral vector system; C9-aldehyde; 9-hydroxy-10(E), 12(Z)-octadecadienoic acid (9-HOD); Nicotiana benthamiana
5.  Exposure of iron foundry workers to polycyclic aromatic hydrocarbons: benzo(a)pyrene-albumin adducts and 1-hydroxypyrene as biomarkers for exposure. 
Exposure to polycyclic aromatic hydrocarbons (PAHs) in foundry workers has been evaluated by determination of benzo(a)pyrene-serum albumin adducts and urinary 1-hydroxypyrene. Benzo(a)pyrene binding to albumin and 1-hydroxypyrene were quantitatively measured by enzyme linked immunosorbent assay (ELISA) and reverse phase high performance liquid chromatography (HPLC), respectively. 70 male foundry workers and 68 matched controls were investigated. High and low exposure groups were defined from breathing zone hygienic samples, consisting of 16 PAH compounds in particulate and gaseous phase. Mean total PAH was 10.40 micrograms/m3 in the breathing zone, and mean dust adsorbed PAH was 0.15 microgram/m. All carcinogenic PAH was adsorbed to dust. Median benzo(a)pyrene-albumin adduct concentrations (10-90% percentiles) were similar in foundry workers (smokers 0.55 (0.27-1.00) and non-smokers 0.58 (0.17-1.15)) pmol/mg albumin and age matched controls (smokers 0.57 (0.16-1.45) and non-smokers 0.70 (0.19-1.55) pmol/mg albumin). Median 1-hydroxypyrene concentrations were significantly higher (P < 0.0001) in smoking and non-smoking foundry workers (0.022 (0.006-0.075) and 0.027 (0.006-0.164)) mumol/mol creatinine than in smoking and non-smoking controls (0 (0-0.022) and 0 (0-0.010) mumol/mol creatinine). Dose-response relations between total PAH, pyrene, carcinogenic PAHs, and 1-hydroxypyrene for smokers, and polycyclic aromatic hydrocarbons adsorbed to dust for non-smokers are suggested. Exposure to PAHs adsorbed to dust showed an additive effect. There was no correlation between the concentrations of 1-hydroxypyrene and benzo(a)pyrene-albumin adducts. The change in 1-hydroxypyrene over a weekend was also studied. Friday morning median 1-hydroxypyrene concentrations were significantly higher in both smokers and non-smokers (0.021 (0-0.075) and 0.027 (0.06-0.164)) mumol/mol creatinine than Monday morning median concentrations (0.007 (0-0.021) and 0.008 (0-0.021) mumol/mol creatinine). Smoking did not affect the concentrations of 1-hydroxypyrene or benzo(a)pyrene-albumin adducts. These data suggest that 1-hydroxypyrene is a sensitive biomarker for low dose PAH exposure. Exposure to PAHs may be aetiologically related to increased risk of lung cancer in foundry workers.
PMCID: PMC1128029  PMID: 7951774
6.  Octa­butyl­bis­(μ2-2-chloro-5-nitro­benzoato)bis­(2-chloro-5-nitro­benzoato)di-μ3-oxido-tetra­tin(IV) 
The title complex, [Sn4(C4H9)8(C7H3ClNO4)4O2], is a cluster formed by a crystallographic inversion center around the central Sn2O2 ring. Both of the two independent Sn atoms are five-coordinated, with distorted trigonal–bipyramidal SnC2O3 geometries. One Sn atom is coordinated by two butyl groups, one O atom of the benzoate anion and two bridging O atoms, whereas the other Sn atom is coordinated by two butyl groups, two O atoms of the benzoate anions and a bridging O atom. The O atoms of the bridging benzoate anion are disordered over two sites with an occupancy ratio of 0.862 (12):0.138 (12). One of the butyl groups coordinated to the Sn2O2 ring is disordered over two sites with an occupancy ratio of 0.780 (8):0.220 (8), whereas both of the two butyl groups coordinated to the other Sn atom are disordered over two sites with occupancy ratios of 0.788 (5):0.212 (5) and 0.827 (10):0.173 (10). All the butyl groups are equatorial with respect to the SnO3 trigonal plane. In the crystal, complex mol­ecules are stacked down [010] with weak inter­molecular C—H⋯π inter­actions stabilizing the crystal structure.
PMCID: PMC3011528  PMID: 21589351
7.  A QM/MM Investigation of the Chemical Reaction in Dpo4 Reveals Water-Dependent Pathways and Requirements for Active Site Reorganization 
Journal of the American Chemical Society  2008;130(40):13240-13250.
The nucleotidyl-transfer reaction coupled with the conformational transitions in DNA polymerases is critical for maintaining the fidelity and efficiency of DNA synthesis. We examine here the possible reaction pathways of a Y-family DNA polymerase, Sulfolobus solfataricus DNA polymerase IV (Dpo4), for the correct insertion of dCTP opposite 8-oxoguanine using the quantum mechanics/molecular mechanics (QM/MM) approach, both from a chemistry-competent state and a crystal closed state. The latter examination is important for understanding pre-chemistry barriers to interpret the entire enzyme mechanism, since the crystal closed state is not an ideal state for initiating the chemical reaction. The most favorable reaction path involves initial deprotonation of O3′H via two bridging water molecules to O1A, overcoming an overall potential energy barrier of approximately 20.0 kcal/mol. The proton on O1A-Pα then migrates to the γ-phosphate oxygen of the incoming nucleotide as O3′ attacks Pα, and the Pα – O3A bond breaks. The other possible pathway in which the O3′H proton is transferred directly to O1A on Pα has an overall energy barrier of 25.0 kcal/mol. In both reaction paths, the rate-limiting step is the initial deprotonation, and the trigonal-bipyramidal configuration for Pα occurs during the concerted bond formation (O3′–Pα) and breaking (Pα–O3A), indicating the associative nature of the chemical reaction. In contrast, the Dpo4/DNA complex with an imperfect active-site geometry corresponding to the crystal state must overcome a much higher activation energy barrier (29.0 kcal/mol) to achieve a tightly organized site due to hindered O3′H deprotonation stemming from larger distances and distorted conformation of the proton acceptors. This significant difference demonstrates that the pre-chemistry reorganization in Dpo4 costs approximately 4.0 to 9.0 kcal/mol depending on the primer terminus environment. Compared to the higher fidelity DNA polymerase β from the X-family, Dpo4 has a higher chemical reaction barrier (20.0 vs. 15.0 kcal/mol) due to the more solvent-exposed active site.
PMCID: PMC3195406  PMID: 18785738
8.  Novel Organotin(IV) Schiff Base Complexes with Histidine Derivatives: Synthesis, Characterization, and Biological Activity 
Five novel tin Schiff base complexes with histidine analogues (derived from the condensation reaction between L-histidine and 3,5-di-tert-butyl-2-hydroxybenzaldehyde) have been synthesized and characterized. Characterization has been completed by IR and high-resolution mass spectroscopy, 1D and 2D solution NMR (1H, 13C  and 119Sn), as well as solid state 119Sn NMR. The spectroscopic evidence shows two types of structures: a trigonal bipyramidal stereochemistry with the tin atom coordinated to five donating atoms (two oxygen atoms, one nitrogen atom, and two carbon atoms belonging to the alkyl moieties), where one molecule of ligand is coordinated in a three dentate fashion. The second structure is spectroscopically described as a tetrahedral tin complex with four donating atoms (one oxygen atom coordinated to the metal and three carbon atoms belonging to the alkyl or aryl substituents), with one molecule of ligand attached. The antimicrobial activity of the tin compounds has been tested against the growth of bacteria in vitro to assess their bactericidal properties. While pentacoordinated compounds 1, 2, and 3 are described as moderate effective to noneffective drugs against both Gram-positive and Gram-negative bacteria, tetracoordinated tin(IV) compounds 4 and 5 are considered as moderate effective and most effective compounds, respectively, against the methicillin-resistant Staphylococcus aureus strains (Gram-positive).
PMCID: PMC3707209  PMID: 23864839
9.  Structure and Ligand Based Drug Design Strategies in the Development of Novel 5-LOX Inhibitors  
Current Medicinal Chemistry  2012;19(22):3763-3778.
Lipoxygenases (LOXs) are non-heme iron containing dioxygenases involved in the oxygenation of polyunsaturated fatty acids (PUFAs) such as arachidonic acid (AA). Depending on the position of insertion of oxygen, LOXs are classified into 5-, 8-, 9-, 12- and 15-LOX. Among these, 5-LOX is the most predominant isoform associated with the formation of 5-hydroperoxyeicosatetraenoic acid (5-HpETE), the precursor of non-peptido (LTB4) and peptido (LTC4, LTD4, and LTE4) leukotrienes. LTs are involved in inflammatory and allergic diseases like asthma, ulcerative colitis, rhinitis and also in cancer. Consequently 5-LOX has become target for the development of therapeutic molecules for treatment of various inflammatory disorders. Zileuton is one such inhibitor of 5-LOX approved for the treatment of asthma.
In the recent times, computer aided drug design (CADD) strategies have been applied successfully in drug development processes. A comprehensive review on structure based drug design strategies in the development of novel 5-LOX inhibitors is presented in this article. Since the crystal structure of 5-LOX has been recently solved, efforts to develop 5-LOX inhibitors have mostly relied on ligand based rational approaches. The present review provides a comprehensive survey on these strategies in the development of 5-LOX inhibitors.
PMCID: PMC3480706  PMID: 22680930
Arachidonic acid; 5-LOX; asthma; drug design; pharmacophore; QSAR; scaffold hopping; pseudoreceptor.
10.  Isomeric differentiation of polycyclic aromatic hydrocarbons using silver nitrate reactive desorption electrospray ionization mass spectrometry 
Polycyclic aromatic hydrocarbons (PAHs) are nonpolar and difficult to detect by desorption electrospray ionization. We present a new detection method based on cationization with silver ions, which has the added advantage of being able to differentiate PAHs with the same mass but different structure.
9,10-Diphenylanthracene and triptycene, in addition to four different groups of PAH isomers: (1) anthracene and phenanthrene, (2) pyrene and fluoranthene, (3) benz[a]anthracene, benz[b]anthracene (tetracene), and chrysene (4) benzo[a]pyrene and benzo[k]fluoranthene, were deposited on a paper surface and bombarded with methanol droplets containing silver nitrate. The resulting microdroplets entered a quadruple mass spectrometer for mass analysis.
The mass spectrum shows [PAH]+, [Ag + OH + PAH]+, and [Ag(PAH)n]+ n (n = 1, 2) (and [PAH + O2]+ in the case of benz[b]anthracene) ions. PAHs having a bay structure, such as phenanthrene, showed a different tendency to interact with silver ions from those PAHs having a linear arrangement of the fused benzene rings, such as anthracene. The ratios of the [PAH]+ peak intensity to that of [Ag–PAH]+, [Ag + OH + PAH]+, [Ag(PAH)2]+, and [PAH + O2]+ were used to differentiate the PAH isomers sharing the same molecular formula with different structures. For isomeric mixtures the [PAH]+ to [Ag + OH + PAH]+ ratio was found to be the most useful parameter. The uncertainty in the mole fraction of an isomeric mixture was ±0.09, 0.13, ±0.25, and ±0.1 for phenanthrene-anthracene, fl benz[a] anthracene-chrysene, and benzo[a]pyrene-benzo[k]fluoranthene, respectively.
A simple method has been developed for the detection of PAHs in desorption electrospray ionization mass spectrometry based on Ag(I) cationization. The method showed a capability to differentiate PAHs isomers (having the same molecular mass) in isomeric mixture with an uncertainty in the mole fraction of about 0.1. At high inlet temperature and voltage, this method showed better sensitivity but less ability to differentiate between ± isomeric species.
PMCID: PMC4145873  PMID: 22847697
11.  Linoleic Acid-Induced Ultra-Weak Photon Emission from Chlamydomonas reinhardtii as a Tool for Monitoring of Lipid Peroxidation in the Cell Membranes 
PLoS ONE  2011;6(7):e22345.
Reactive oxygen species formed as a response to various abiotic and biotic stresses cause an oxidative damage of cellular component such are lipids, proteins and nucleic acids. Lipid peroxidation is considered as one of the major processes responsible for the oxidative damage of the polyunsaturated fatty acid in the cell membranes. Various methods such as a loss of polyunsaturated fatty acids, amount of the primary and the secondary products are used to monitor the level of lipid peroxidation. To investigate the use of ultra-weak photon emission as a non-invasive tool for monitoring of lipid peroxidation, the involvement of lipid peroxidation in ultra-weak photon emission was studied in the unicellular green alga Chlamydomonas reinhardtii. Lipid peroxidation initiated by addition of exogenous linoleic acid to the cells was monitored by ultra-weak photon emission measured with the employment of highly sensitive charged couple device camera and photomultiplier tube. It was found that the addition of linoleic acid to the cells significantly increased the ultra-weak photon emission that correlates with the accumulation of lipid peroxidation product as measured using thiobarbituric acid assay. Scavenging of hydroxyl radical by mannitol, inhibition of intrinsic lipoxygenase by catechol and removal of molecular oxygen considerably suppressed ultra-weak photon emission measured after the addition of linoleic acid. The photon emission dominated at the red region of the spectrum with emission maximum at 680 nm. These observations reveal that the oxidation of linoleic acid by hydroxyl radical and intrinsic lipoxygenase results in the ultra-weak photon emission. Electronically excited species such as excited triplet carbonyls are the likely candidates for the primary excited species formed during the lipid peroxidation, whereas chlorophylls are the final emitters of photons. We propose here that the ultra-weak photon emission can be used as a non-invasive tool for the detection of lipid peroxidation in the cell membranes.
PMCID: PMC3143142  PMID: 21799835
12.  Chemical characterization and bioactivity of polycyclic aromatic hydrocarbons from non-oxidative thermal treatment of pyrene-contaminated soil at 250-1,000 degrees C. 
Environmental Health Perspectives  2000;108(8):709-717.
In this paper we report yields, identities, and mutagenicities of products from heating a polycyclic aromatic hydrocarbon (PAH)-contaminated, Superfund-related synthetic soil matrix without exogenous oxygen. We heated batch samples of soil pretreated with 5.08 wt% (by weight) pyrene in a tubular furnace under a constant flow of helium gas at 250, 500, 750, and 1,000 +/- 20 degrees C. Dichloromethane (DCM) extracts of cooled residues of heated soil and of volatiles condensed on a cold finger after 1 sec residence time at furnace temperature were assayed gravimetrically and analyzed for PAH by HPLC, HPLC coupled to mass spectrometry, and gas chromatography coupled to mass spectrometry. All four temperatures volatilized pyrene and generated other PAHs, including alkylated pyrenes. We detected bioactive PAHs in the product volatiles: cyclopenta[cd]pyrene (CPP) at 750 and 1,000 degrees C and benzo[a]pyrene (BaP) at 1,000 degrees C. We found a clean soil residue, i.e., no pyrene or other DCM extracts, only at 750 degrees C. Control experiments with uncontaminated soil, pyrene, and Ottawa sand plus 4.89 wt% pyrene revealed no CPP or BaP production from soil itself, but these experiments imply that pyrene interactions with soil, e.g., soil-bound silica, stimulate CPP and BaP production. We detected mutagenicity to human diploid lymphoblasts (in vitro) in volatiles from 1,000 degrees C heating of soil plus pyrene and sand plus pyrene, and in the residue from 500 degrees C heating of soil plus pyrene. Three plausible pathways for pyrene conversion to other PAHs are a) a reaction with light gas species, e.g., soil- or pyrene-derived acetylene; b) loss of C(2)-units followed by reaction with a PAH; and c) dimerization with further molecular weight growth via cyclodehydrogenation. This study shows that thermal treatment of PAH-polluted soil may generate toxic by-products that require further cleanup by oxidation or other measures.
PMCID: PMC1638299  PMID: 10964790
13.  Prenatal Polycyclic Aromatic Hydrocarbon Exposure Leads to Behavioral Deficits and Downregulation of Receptor Tyrosine Kinase, MET 
Toxicological Sciences  2010;118(2):625-634.
Gene by environment interactions (G × E) are thought to underlie neurodevelopmental disorder, etiology, neurodegenerative disorders, including the multiple forms of autism spectrum disorder. However, there is limited biological information, indicating an interaction between specific genes and environmental components. The present study focuses on a major component of airborne pollutants, polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene [B(a)P], which negatively impacts cognitive development in children who have been exposed in utero. In our study, prenatal exposure of Cprlox/lox timed-pregnant dams to B(a)P (0, 150, 300, and 600 μg/kg body weight via oral gavage) on embryonic day (E14–E17) consistent with our susceptibility-exposure paradigm was combined with the analysis of a replicated autism risk gene, the receptor tyrosine kinase, Met. The results demonstrate a dose-dependent increase in B(a)P metabolite generation in B(a)P-exposed Cprlox/lox offspring. Additionally, a sustained persistence of hydroxy metabolites during the onset of synapse formation was noted, corresponding to the peak of Met expression. Prenatal B(a)P exposure also downregulated Met RNA and protein levels and dysregulated normal temporal patterns of expression during synaptogenesis. Consistent with these data, transcriptional cell–based assays demonstrated that B(a)P exposure directly reduces human MET promoter activity. Furthermore, a functional readout of in utero B(a)P exposure showed a robust reduction in novel object discrimination in B(a)P-exposed Cprlox/lox offspring. These results confirm the notion that common pollutants, such as the PAH B(a)P, can have a direct negative impact on the regulated developmental expression of an autism risk gene with associated negative behavioral learning and memory outcomes.
PMCID: PMC2984527  PMID: 20889680
gene × environment interaction; autism spectrum disorders; polycyclic aromatic hydrocarbon; benzo(a)pyrene; susceptibility-exposure paradigm; novel object discrimination behavioral task; B(a)P metabolites; in utero exposures; behavioral neurotoxicity
14.  Poly[(μ5-5-carboxylatotetrahydrofuran-2,3,4-tricarboxylic acid)sodium] 
The search for the novel metal-organic frameworks (MOFs) materials using tetra­hydro­furan-2,3,4,5-tetra­carboxylic acid (THFTCA) as a versatile multi-carboxyl ligand, lead to the synthesis and the structure determination of the title compound, [Na(H3THFTCA)] or [Na(C8H7O9)]n, which was obtained by a solution reaction at room temperature. The ligand is mono-deprotonated, coordinating five sodium ions through one furan oxygen atom and six carboxyl oxygen atoms. The sodium ion exhibits a distorted penta­gonal-bipyramidal NaO7 geometry consisting of seven O atoms derived from five surrounding ligands. Two adjacent pentagonal bipyramids share an O—O edge, forming a dinuclear sodium cluster. Finally, these clusters are effectively linked by the carboxyl groups of THFTCA ligands, forming a firm metal organic framework and O—H⋯O hydrogen bonds contribute to the crystal packing.
PMCID: PMC2971171  PMID: 21578156
15.  The influence of diesel exhaust on polycyclic aromatic hydrocarbon-induced DNA damage, gene expression and tumor initiation in Sencar mice in vivo 
Cancer letters  2008;265(1):135-147.
The carcinogenic effects of individual polycyclic aromatic hydrocarbons (PAH) are well established. However, their potency within an environmental complex mixture is uncertain. We evaluated the influence of diesel exhaust particulate matter on PAH-induced cytochrome P450 (CYP) activity, PAH-DNA adduct formation, expression of certain candidate genes and the frequency of tumor initiation in the two-stage Sencar mouse model. To this end, we monitored the effects of treatment of mice with diesel exhaust, benzo[a]pyrene (BP), dibenzo[a,l]pyrene (DBP), or a combination of diesel exhaust with either carcinogenic PAH. The applied diesel particulate matter (SRM1975) altered the tumor initiating potency of DBP: a statistically significant decrease in overall tumor and carcinoma burden was observed following 25 weeks of promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA), compared with DBP exposure alone. From those mice that were treated at the beginning of the observation period with 2 nmol DBP all survivors developed tumors (9 out of 9 animals, 100%). Among all tumors counted at the end, 9 carcinomas were detected and an overall tumor incidence of 2.6 tumors per tumor-bearing animal (TBA) was determined. By contrast, co-treatment of DBP with 50 mg SRM1975 led to a tumor rate of only 66% (19 out of 29 animals), occurrence of only 3 carcinomas in 29 animals and an overall rate of 2.1 tumors per TBA (P = 0.04). In contrast to the results with DBP, the tumor incidence induced by 200 nmol BP was found slightly increased when co-treatment with SRM1975 occurred (71% vs. 85% after 25 weeks). Despite this difference in tumor incidence, the numbers of carcinomas and tumors per TBA did not differ statistically significant between both treatment groups possibly due to the small size of the BP treatment group. Since bioactivation of DBP, but not BP, predominantly depends on CYP1B1 enzyme activity, SRM1975 affected PAH-induced carcinogenesis in an antagonistic manner when CYP1B1-mediated bioactivation was required. The explanation most likely lies in the much stronger inhibitory effects of certain PAHs present in diesel exhaust on CYP1B1 compared to CYP1A1. In the present study we also found molecular markers such as highly elevated AKR1C21 and TNFRSF21 gene expression levels in tumor tissue derived from animals co-treated with SRM1975 plus DBP. Therefore we validate microarray data as a source to uncover transcriptional signatures that may provide insights into molecular pathways affected following exposure to environmental complex mixtures such as diesel exhaust particulates.
PMCID: PMC2519885  PMID: 18353537
DNA adducts; carcinogenesis; diesel exhaust; PAH; cytochrome P450
16.  Cannabidiol-2′,6′-dimethyl Ether as an Effective Protector of 15-Lipoxygenase-Mediated Low-Density Lipoprotein Oxidation in Vitro 
Biological & pharmaceutical bulletin  2011;34(8):1252-1256.
15-Lipoxygenase (15-LOX) is one of the key enzymes responsible for the formation of oxidized low-density lipoprotein (ox-LDL), a major causal factor for atherosclerosis. Both enzymatic (15-LOX) and non-enzymatic (Cu2+) mechanisms have been proposed for the production of ox-LDL. We have recently reported that cannabidiol-2′,6′-dimethyl ether (CBDD) is a selective and potent inhibitor of 15-LOX-catalyzed linoleic acid oxygenation (Takeda et al., Drug Metab. Dispos., 37, 1733–1737 (2009)). In the LDL, linoleic acid is present as cholesteryl linoleate, the major fatty acid esterified to cholesterol, and is susceptible to oxidative modification by 15-LOX or Cu2+. In this investigation, we examined the efficacy of CBDD on i) 15-LOX-catalyzed oxygenation of cholesteryl linoleate, and ii) ox-LDL formation catalyzed by 15-LOX versus Cu2+-mediated non-enzymatic generation of this important mediator. The results obtained demonstrate that CBDD is a potent and selective inhibitor of ox-LDL formation generated by the 15-LOX pathway. These studies establish CBDD as both an important experimental tool for characterizing 15-LOX-mediated ox-LDL formation, and as a potentially useful therapeutic agent for treatment of atherosclerosis.
PMCID: PMC4012644  PMID: 21804214
cannabidiol-2′; 6′-dimethyl ether; 15-lipoxygenase; low-density lipoprotein; atherosclerosis; cannabinoid
17.  Omega-3 fatty acids are oxygenated at the n-7 carbon by the lipoxygenase domain of a fusion protein in the cyanobacterium Acaryochloris marina 
Biochimica et biophysica acta  2009;1801(1):58-63.
Lipoxygenases (LOX) are found in most organisms that contain polyunsaturated fatty acids, usually existing as individual genes although occasionally encoded as a fusion protein with a catalase-related hemoprotein. Such a fusion protein occurs in the cyanobacterium Acaryochloris marina and herein we report the novel catalytic activity of its LOX domain. The full-length protein and the C-terminal LOX domain were expressed in Escherichia coli, and the catalytic activities characterized by UV, HPLC, GC-MS, and CD. All omega-3 polyunsaturates were oxygenated by the LOX domain at the n-7 position and with R stereospecificity: α-linolenic and the most abundant fatty acid in A. marina, stearidonic acid (C18.4ω3), are converted to the corresponding 12R-hydroperoxides, eicosapentaenoic acid to its 14R-hydroperoxide, and docosahexaenoic acid to its 16R-hydroperoxide. Omega-6 polyunsaturates were oxygenated at the n-10 position, forming 9R-hydroperoxy-octadecadienoic acid from linoleic acid and 11R-hydroperoxy-eicosatetraenoic acid from arachidonic acid. The metabolic transformation of stearidonic acid by the full-length fusion protein entails its 12R oxygenation with subsequent conversion by the catalase-related domain to a novel allene epoxide, a likely precursor of cyclopentenone fatty acids or other signaling molecules (Gao et al, J. Biol. Chem. 284:22087-98, 2009). Although omega-3 fatty acids and lipoxygenases are of widespread occurrence, this appears to be the first description of a LOX-catalyzed oxygenation that specifically utilizes the terminal pentadiene of omega-3 fatty acids.
PMCID: PMC2787963  PMID: 19786119
Acaryochloris marina; lipoxygenase; hydroperoxide; omega-3 fatty acids; linolenic acid; stearidonic acid; GC-MS; chiral analysis
18.  Bis(μ2-2-amino-5-nitro­benzoato)bis­(2-amino-5-nitro­benzoato)octa­butyldi-μ3-oxido-tetra­tin(IV) 
In the title complex, [Sn4(C4H9)8(C7H5N2O4)4O2], all four SnIV atoms are five-coordinated with distorted trigonal–bipyramidal SnC2O3 geometries. Two SnIV atoms are coordin­ated by two butyl groups, one benzoate O atom and two bridging O atoms, whereas the other two SnIV atoms are coordinated by two butyl groups, two benzoate O atoms and a bridging O atom. All the butyl groups are equatorial with respect to the SnO3 trigonal plane. In the crystal, mol­ecules are linked into a two-dimensional layer parallel to the ab plane by inter­molecular N—H⋯O and C—H⋯O hydrogen bonds and further stabilized by a π–π inter­action [centroid–centroid distance = 3.6489 (11) Å]. Intra­molecular N—H⋯O and C—H⋯O hydrogen bonds stabilize the mol­ecular structure. Two of the butyl groups are each disordered over two sets of sites with site-occupancy ratios of 0.510 (4):0.490 (4) and 0.860 (5):0.140 (5).
PMCID: PMC3212181  PMID: 22090883
19.  Sample preparation procedure for the determination of polycyclic aromatic hydrocarbons in petroleum vacuum residue and bitumen 
Analytical and Bioanalytical Chemistry  2011;401(3):1059-1069.
This paper describes a novel method of sample preparation for the determination of trace concentrations of polycyclic aromatic hydrocarbons (PAHs) in high-boiling petroleum products. Limits of quantitation of the investigated PAHs in materials of this type range from tens of nanograms per kilogram to <20 μg/kg. The studies revealed that in order to separate most of interferences from the analytes without a significant loss of PAHs, it is necessary to use size exclusion chromatography as the first step of sample preparation, followed by adsorption using normal-phase liquid chromatography. The use of orthogonal separation procedure described in the paper allows the isolation of only a group of unsubstituted and substituted aromatic hydrocarbons with a specific range of molar mass. The lower the required limit of quantitation of PAHs, the larger is the scale of preparative liquid chromatography in both steps of sample preparation needed. The use of internal standard allows quantitative results to be corrected for the degree of recovery of PAHs during the sample preparation step. Final determination can be carried out using HPLC-FLD, GC-MS, or HPLC-UV–VIS/DAD. The last technique provides a degree of identification through the acquired UV–VIS spectra.
FigureChromatograms obtained using UV-DAD detection with wavelength programming (A) and fluorimetric detection (B) for the separation of 18 PAH standards ((A) and (B)) and the fraction containing PAHs from road asphalt 50/70 prepared according to the procedure described in this work (C). Peak designation: 1 naphthalene, 2 acenaphthylene, 3 acenaphthene, 4 fluorene, 5 phenanthrene, 6 anthracene, 7 fluoranthene, 8 pyrene, 9 benzo[a]anthracene, 10 chrysene, 11 benzo[b]fluoranthene, 12 benzo[k]fluoranthene, 13 benzo[a]pyrene, 14 dibenzo[a,h]anthracene, 15 indeno[1,2,3-cd]pyrene, 16 benzo[ghi]perylene, 17 benzo[j]fluoranthene, 18 benzo[e]pyrene,19 highly polar components of road asphalt 50/70 eluted during backflush. BF backflush point
PMCID: PMC3140947  PMID: 21647802
Sample preparation techniques; Multidimensional liquid chromatography; Group separation; Size exclusion chromatography; Normal-phase adsorption chromatography; High-boiling petroleum products; Polycyclic aromatic hydrocarbons (PAHs); Trace analysis
20.  Bis(hydrazin-1-ium) bis­(μ2-pyridazine-3,6-dicarboxyl­ato)bis­(aqua­lithiate) octa­aqua­bis­(μ3-pyridazine-3,6-dicarboxyl­ato)tetra­lithium 
The unit cell of the title compound, (N2H5)2[Li2(C6H2N2O4)2(H2O)2]·[Li4(C6H2N2O4)2(H2O)8], comprises two centrosymmetric complexes, one double negatively charged and one neutral, and two mono-protonated hydrazine cations. The anionic complex molecule is a dimer, built of a pair of symmetry-related pyridazine-3,6-dicarboxyl­ate ligands and a pair of LiI ions, each coordinated by two N,O-chelating sites donated by a ligand mol­ecule and an aqua O atom at the apical position. The penta­coordination around the LiI ions is partway between a trigonal–bipyramidal and a square-pyramidal arrangement. The two carb­oxy­lic acid groups of the ligand are deprotonated and one carboxyl­ate O atom of each group is not involved in the coordination, and this applies to both the anionic and the neutral complex. The neutral complex molecule is also composed of a pair of LiI ions and a pair of ligand mol­ecules related by a centre of symmetry. They form a dimeric core in which the penta­coordination of the LiI ions includes two N,O-bonding groups donated by two ligands and an aqua O atom. The penta­coordination is described as partway between a trigonal–bipyramidal and a square-pyramidal arrangement. The coordinated carboxyl­ate group is bidentate–bridging, forming with an Li(H2O)3 unit a neutral tetra­meric mol­ecule. The coordination of the tetra­coordinated LiI ion shows a slightly distorted tetra­hedral geometry. An extended system of O—H⋯O and N—H⋯O hydrogen bonds contributes to the stability of the crystal structure.
PMCID: PMC3297271  PMID: 22412461
21.  Octa-n-butyl-1κ2 C,2κ2 C,3κ2,4κ2 C-bis­(μ-2,3-dibromo­propionato)-1:2κ2 O:O′,3:4κ2 O:O′-bis­(2,3-dibromo­propionato)-1κO,3κO-di-μ3-oxido-1:2:4κ3 O:O:O,2:3:4κ3 O:O:O-tetra­tin(IV) 
In the centrosymmetric tetra­nuclear title complex, [Sn4(C4H9)8(C3H3Br2O2)4O2], one of the two independent Sn atoms is five-coordinated by one O atom of the carboxyl­ate anion, two bridging O atoms and two n-butyl groups in a C2SnO3 distorted trigonal bipyramidal geometry. The other Sn atom also has a distorted trigonal bipyramidal geometry, being coordinated by two O atoms of two carboxyl­ate anions, one bridging O atom and two butyl groups. An inter­esting feature of the crystal structure is the short Sn⋯O [2.756 (4) Å] and O⋯O [2.608 (3) Å] inter­actions. The –BrCH2—CHBr– segments of the two carboxyl­ate anions are disordered over two positions [site occupancies of 0.60 (1)/0.40 (1) and 0.53 (2)/0.47 (2)]. Weak non-directional C—H⋯O inter­actions lead to the formation of infinte chains along the a axis; other weak inter­molecular C—H⋯π inter­actions are also present.
PMCID: PMC2959824  PMID: 21581176
22.  Synthesis, Characterization and Molecular Structures of some Bismuth(III) Complexes with Thiosemicarbazones and Dithiocarbazonic Acid Methylester Derivatives with Activity against Helicobacter Pylori 
Metal-Based Drugs  1995;2(5):271-292.
The reactions of bismuth(III) nitrate pentahydrate and bismuth(III) chloride with heterocyclic thiosemicarbazones and derivatives of dithiocarbazonic acid methylester were used to synthesize the respective bismuth(III) complexes, which could be divided into five groups D-H because of their stoichiometrical properties and their molecular structures. The molecular structure and the near coordination sphere of the bismuth(III) central atom of four representative compounds were determined by single-crystal X-ray studies. Bis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N′,N3,S]bismuth(III) nitrate (5) belongs to group D. The two tridentate ligands and the nitrate ion surround the bismuth atom. The best description of the coordination sphere appears to be that of a distorted trigonal dodecahedron with one position occupied by the lone pair of the bismuth atom. Bis[1-azepanyl-4-(2-thienyl)-2,3-diazapenta-1,3-diene-1-thiolato-N3,S]bismuth(III) nitrate (9) is assigned to complex type E. Here, two deprotonated ligand molecules are coordinated to the bismuth(III) central atom as bidentate ligands. The structure of this complex can best be described as a distorted trigonal antiprism with a five-coordinated central atom. The two triangular faces are formed by the atoms S(4), N(6), O(11) and S(3), N(4) and the lone pair of the central atom. The two chelate rings are almost perpendicular to each other. Complex molecules of group F form dimeric units with bichloro-bridged bismuth atoms. The structure of di-μ-chlorobis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N′,N3,S-chloro]dibismuth(III) (15) can be described as two six-coordinated bismuth atoms, which are bound together via two bridging chlorine atoms. The two bismuth atoms Bi(1) and Bi(1a) and the two bridging chlorine atoms Cl(2) and Cl(2a) form the Bi2Cl2 plane. The two tridentate ligand molecules coordinate via the same atoms as shown in complex 5. In addition, they form two parallel planes, which are perpendicular to the Bi2Cl2 plane. With regard to the center of the Bi(1)-Bi(2) axis they are central point symmetrical, i.e. one pyridine ring lies above and the other beneath the Bi2Cl2 plane. Bismuth(III) chloride and pyridine-2-carboxaldehydethiosemicarbazone 1 b or 2-acetylpyridine-thiosemicarbazone 1 c form complexes of group G. Three chlorine atoms and a bidentate ligand are coordinated to the bismuth(III) central atom. The bidentate ligand bound to the central atom through the N(3) atom and the sulfur atom of the thioketo group. The structure of 18 is completely different from the structures of the bismuth(III) complexes discussed so far and was therefore assigned to group H. The bismuth central atom is coordinated with two ligands, which are bound in different ways. One of them is deprotonated. This ligand is bound to the central atom via the sulfur atom S(3) of the thiolate group and the N(5) atom. An interaction between the sulfur atom of the thiophene ring and the bismuth atom is not possible.The other ligand molecule is not deprotonated. This ligand is bound to the bismuth(III) cation merely via the sulfur atom S(1) of the thioketo group. The best description of the coordination sphere of the bismuth atom is that of a distorted square bipyramidal polyhedron. The square face is formed by the atoms S(3), N(5), Cl(1), the lone pair and the bismuth atom within. The axial positions are occupied by the atoms S(1) and Cl(2). The bond angle between S(1), Bi(1) and Cl(2) differs by about eight degrees from the value determined for a regular square bipyramidal polyhedron of 180 degrees.
Some of the newly synthesized bismuth complexes and three ligands have been tested against several strains of Helicobacter pylori bacteria in an agar dilution test. Almost all of the listed bismuth complexes show excellent inhibitory properties with regard to growth of H. pylori already at low concentrations.
PMCID: PMC2364985  PMID: 18472778
23.  Cancer risk assessment, indicators, and guidelines for polycyclic aromatic hydrocarbons in the ambient air. 
Environmental Health Perspectives  2002;110(Suppl 3):451-488.
Polycyclic aromatic hydrocarbons (PAHs) are formed during incomplete combustion. Domestic wood burning and road traffic are the major sources of PAHs in Sweden. In Stockholm, the sum of 14 different PAHs is 100-200 ng/m(3) at the street-level site, the most abundant being phenanthrene. Benzo[a]pyrene (B[a]P) varies between 1 and 2 ng/m(3). Exposure to PAH-containing substances increases the risk of cancer in humans. The carcinogenicity of PAHs is associated with the complexity of the molecule, i.e., increasing number of benzenoid rings, and with metabolic activation to reactive diol epoxide intermediates and their subsequent covalent binding to critical targets in DNA. B[a]P is the main indicator of carcinogenic PAHs. Fluoranthene is an important volatile PAH because it occurs at high concentrations in ambient air and because it is an experimental carcinogen in certain test systems. Thus, fluoranthene is suggested as a complementary indicator to B[a]P. The most carcinogenic PAH identified, dibenzo[a,l]pyrene, is also suggested as an indicator, although it occurs at very low concentrations. Quantitative cancer risk estimates of PAHs as air pollutants are very uncertain because of the lack of useful, good-quality data. According to the World Health Organization Air Quality Guidelines for Europe, the unit risk is 9 X 10(-5) per ng/m(3) of B[a]P as indicator of the total PAH content, namely, lifetime exposure to 0.1 ng/m(3) would theoretically lead to one extra cancer case in 100,000 exposed individuals. This concentration of 0.1 ng/m(3) of B[a]P is suggested as a health-based guideline. Because the carcinogenic potency of fluoranthene has been estimated to be approximately 20 times less than that of B[a]P, a tentative guideline value of 2 ng/m(3) is suggested for fluoranthene. Other significant PAHs are phenanthrene, methylated phenanthrenes/anthracenes and pyrene (high air concentrations), and large-molecule PAHs such as dibenz[a,h]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, and indeno[1,2,3-cd]pyrene (high carcinogenicity). Additional source-specific indicators are benzo[ghi]perylene for gasoline vehicles, retene for wood combustion, and dibenzothiophene and benzonaphthothiophene for sulfur-containing fuels.
PMCID: PMC1241197  PMID: 12060843
24.  Bis(μ2-4-amino-3-nitro­benzoato)bis­(4-amino-3-nitro­benzoato)octa­butyldi-μ3-oxido-tetra­tin(IV) 
The tetranuclear molecules of the title compound, [Sn4(C4H9)8(C7H5N2O4)4O2], reside on a crystallographic inversion center. Both the two independent Sn atoms are five-coordinate, with distorted trigonal–bipyramidal geometries. One Sn atom is coordinated by two O atoms of the carboxyl­ate anions, one bridging O atom and two butyl groups and the other Sn atom is coordinated by an O atom of the carboxyl­ate anion, two bridging O atoms and two butyl groups. All the butyl groups are equatorial with respect to the SnO3 trigonal plane. The mol­ecular structure is stabilized by intra­molecular N—H⋯O hydrogen bonds. In the crystal, pairs of inter­molecular bifurcated acceptor N—H⋯O and C—H⋯O hydrogen bonds link the mol­ecules into chains along [10]. Weak inter­molecular C—H⋯π and π–π inter­actions [centroid–centroid distance = 3.713 (2) Å] are also observed.
PMCID: PMC3009280  PMID: 21588838
25.  Malonaldehyde formation is not a suitable screening test to detect oxidation in human neutrophils. 
Journal of Clinical Pathology  1981;34(7):800-802.
The thiobarbituric acid (TBA) assay for measuring malonaldehyde (MDA) has been applied to many tissues as a simple means of detecting oxidative damage and prostaglandin synthesis. Human neutrophils, cells known to produce prostaglandins and toxic metabolites of oxygen, were studied to determine if this assay could provide a suitable, rapid, screening test to recognise states of metabolic activation, to monitor prostaglandin synthesis, or to identify the presence of oxidative damage. Malonaldehyde could not be detected after a variety of manipulations. Thus, it seems unlikely that the thiobarbituric acid assay, as performed here, will be useful for evaluating oxidative damage in human neutrophils.
PMCID: PMC493824  PMID: 7263907

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