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PubMed2005

A chromism-based assay (CHROBA) technique for in situ detection of protein kinase activity.

A unique chromism-based assay technique (CHROBA) using photochromic spiropyran-containing peptides has been firstly established for detection of protein kinase A-catalyzed phosphorylation. The alternative method has advantages that avoid isolation and/or immobilization of kinase substrates to remove excess reagents including nonreactive isotope-labeled ATP or fluorescently-labeled anti-phosphoamino acid antibodies from the reaction mixture. Such a novel protocol based on thermocoloration of the spiropyran moiety in the peptide can offer not only an efficient screening method of potent kinase substrates but also a versatile analytical tool for monitoring other post-translational modification activities.

Benzopyrans↗
PubMed2005

Thermal decomposition kinetics of the Pb0.25Ba0.75(TNR).H2O complex.

Studies of the non-isothermal decomposition of Pb(0.25)Ba(0.75)(TNR).H(2)O (TNR=2,4,6-trinitro-1,3-dihydroxy-benzene) were carried out by means of TG-DTA, DSC and IR techniques. The thermal decomposition mechanism and the associated kinetics have been investigated. The kinetic parameters were obtained from the analysis of the DSC curves by integral and differential methods. The most probable kinetic model function of the dehydration reaction of Pb(0.25)Ba(0.75)(TNR).H(2)O were suggested by comparison of the kinetic parameters.

Barium Compounds↗
PubMed1980

Organic acids produced by self-sustaining coacervates in presence of p-nitroaniline and p-phenylene-diamine.

Oleic and malonic acids were found in control samples while p-nitroaniline addition induced production of tricarballylic acid in eight and twelve days exposed samples. Fumaric and citric acids were found in sporadic instances. Addition of p-phenylene diamine to the mixture showed a degeneration process in organic acid production. In some cases production of fumaric acid was positive.

Aniline Compounds↗
PubMed2002

Molecular triads composed of ferrocene, C60, and nitroaromatic entities: electrochemical, computational, and photochemical investigations.

Synthesis and physicochemical characterization of a series of molecular triads composed of ferrocene, C(60), and nitroaromatic entities are reported. Electrochemical studies revealed multiple redox processes involving all three redox active ferrocene, C(60), and nitrobenzene entities. Up to eight redox couples within the accessible potential window of o-dichlorobenzene containing 0.1 M (TBA)ClO(4) are observed. A comparison between the measured redox potentials with those of the starting compounds revealed absence of any significant electronic interactions between the different redox entities. The geometric and electronic structure of the triads are elucidated by using ab initio B3LYP/3-21G methods. In the energy-optimized structures, as predicted by electrochemical studies, the first HOMO orbitals are found to be located on the ferrocene entity, while the first LUMO orbitals are mainly on the C(60) entity. The coefficients of the subsequent LUMO orbitals track the observed site of electrochemical reductions of the triads. The photochemical events of the triads are probed by both steady-state and time-resolved techniques. The steady-state emission intensities of the triads and the starting dyad, 2-(ferrocenyl)fulleropyrrolidine, are found to be completely quenched compared to fulleropyrrolidine bearing no redox active substituents. The subpicosecond and nanosecond transient absorption spectral studies revealed efficient charge separation (and rapid charge recombination) in the triads, and this has been attributed to the close spacing of the redox entities of the triad to one another.

Computational Biology↗
PubMed2004

Basic hydrolysis of crystal violet in beta-cyclodextrin/surfactant mixed systems.

The basic hydrolysis of crystal violet (CV) in mixed systems consisting of beta-cyclodextrin (beta-CD) and a micelle-forming surfactant, cetyltrimethylammonium chloride (CTACl), has been studied. beta-CD was found to catalyze the basic hydrolysis of CV through the interaction of its hydroxyl group, in its deprotonated form, with the carbocation in the complexed substrate. The addition of small amounts of CTACl, with [CTACl] below the critical micelle concentration, to beta-CD solutions does not have an effect upon the observed rate constant for the basic hydrolysis of CV. This behavior is different from that observed for the alkaline hydrolysis of N-methyl-N-nitroso-p-toluenesulfonamide and nitrophenyl acetates in mixed beta-CD/cationic surfactant systems. The proposed mechanism allows us to explain the experimental results on the basis of the high percentage of uncomplexed beta-CD in equilibrium with the micellar system, the low CV concentration, and the high value for the binding constant of CV by beta-CD.

Binding Sites↗
PubMed1962

Nitrification by Aspergillus flavus.

Marshall, K. C. (Cornell University, Ithaca, N. Y.) and M. Alexander. Nitrification by Aspergillus flavus. J. Bacteriol. 83:572-578. 1962.-Aspergillus flavus has been shown to produce bound hydroxylamine, nitrite, and nitrate when grown in peptone, amino acid, or buffered ammonium media. Free hydroxylamine was not detected in these cultures, but it was found in an unbuffered ammonium medium in which neither nitrite nor nitrate was formed. Evidence was obtained for the presence of beta-nitropropionic acid in the filtrate of an actively nitrifying culture. Alumina treatment of an ammonium medium prevented the formation by growing cultures of nitrite and nitrate but not bound hydroxylamine. The effect of alumina treatment was reversed by the addition of 10(-3)m CeCl(3) to the medium. Extracts of the fungus contained peroxidase and an enzyme capable of catalyzing the production of nitrite from beta-nitropropionic acid. The nitrite-forming enzyme is apparently specific for beta-nitropropionate; no activity was found with nitromethane, nitroethane, and nitropropane as substrates. Nitrate was not reduced to nitrite nor was nitrite oxidized to nitrate by the hyphal extracts. The significance of these observations in nitrification by A. flavus is discussed.

Amino Acids↗
PubMed1995

Reduction of azo dyes and nitroaromatic compounds by bacterial enzymes from the human intestinal tract.

Several anaerobic bacteria from the human intestinal tract are capable of reducing azo dyes and nitropolycyclic aromatic hydrocarbons to the corresponding aromatic amines with enzymes that have azoreductase and nitroreductase activities. The majority of bacteria with these activities belong to the genera Clostridium and Eubacterium. The azoreductases and nitroreductases from three Clostridium strains and one Eubacterium strain were studied. Both enzymes were produced constitutively in each of the bacteria; the enzymes from various bacteria had different electrophoretic mobilities. The azoreductases from all of the bacteria had immunological homology, as was evident from the cross-reactivity of an antibody raised against the azoreductase of C. perfringens with azoreductases from other bacteria. Comparison of azoreductases and nitroreductases showed that they both had identical electrophoretic mobilities on polyacrylamide gels and reacted with the antibody against the azoreductase from C. perfringens. Furthermore, the nitroaromatic compounds competitively inhibited the azoreductase activity. The data indicate that the reduction of both nitroaromatic compounds and azo dyes may be carried out by the same enzyme, which is possibly a flavin adenine dinucleotide dehydrogenase that is synthesized throughout the cell and not associated with any organized subcellular structure.

Azo Compounds↗
PubMed1987

Comparative metabolism and DNA binding of 6-nitro-5-methylchrysene and 5-methylchrysene.

The metabolic activation in mouse skin of the strong carcinogen, 5-methylchrysene (5-MeC) was compared to that of the inactive compound, 6-nitro-5-methylchrysene (6-NO2-5-MeC). Metabolites of 6-NO2-5-MeC, formed using rat liver homogenates, were identified based on their spectral properties and were used as markers for studies performed in vivo. In mouse epidermis in vivo, the identified metabolites of 6-NO2-5-MeC were trans-1,2-dihydro-1,2-dihydroxy-6-nitro-5-methylchrysene (6-NO2-5-MeC-1,2-diol), the precursor to a bay region dihydrodiol epoxide, trans-9,10-dihydro-9,10-dihydroxy-6-nitro-5-methylchrysene, and 6-nitro-5-hydroxymethylchrysene. The levels of 6-NO2-5-MeC-1,2-diol formed in mouse epidermis from 6-NO2-5-MeC were greater than those of the proximate carcinogen trans-1,2-dihydro-1,2-dihydroxy-5-methylchrysene (5-MeC-1,2-diol) formed from 5-MeC. The further metabolism of 6-NO2-5-MeC-1,2-diol was examined in mouse epidermis under conditions similar to those described previously for 5-MeC-1,2-diol. The extents of formation of 1,2,3,4-tetraols from both dihydrodiols were similar. The chromatographic patterns of DNA adducts formed in mouse epidermis from 6-NO2-5-MeC and 5-MeC were qualitatively similar; however, the extent of formation of DNA adducts from 5-MeC was 15-fold greater than from 6-NO2-5-MeC. The reactions between calf thymus DNA and the bay region 1,2-diol-3,4-epoxides of 5-MeC and 6-NO2-5-MeC were compared; the levels of adducts formed from the bay region diol epoxide of 5-MeC were about four times greater than those formed from the bay region diol epoxide of 6-NO2-5-MeC. The results indicate that the relatively low DNA binding in vivo of 6-NO2-5-MeC may be responsible for its apparent lack of tumorigenicity compared to 5-MeC. It is likely that nitro substitution at the 6-position of 5-MeC interferes with the structural requirements of the 1,2-diol-3,4-epoxide which are necessary for specific DNA interactions.

Animals↗
PubMed1975

Studies on hypersensitivity to "para group".

The author reports the results of patch tests using various aromatic compounds in subjects sensitized to PPD. It was found that aromatic nitro and hydroxyl compounds as well as secondary and tertiary amines do not cause cross-reactions. Positive reactions were obtained only with primary aromatic amines, independently of the position of the amino group in the ring-para, ortho or meta.

Amines↗
PubMed2006

Hydrazones of 2-aryl-quinoline-4-carboxylic acid hydrazides: synthesis and preliminary evaluation as antimicrobial agents.

A new series of 2-arylquinoline-4-carboxylic acid hydrazide-hydrazones was synthesized using an appropriate synthetic route. All the target compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus as an example for Gram-positive bacteria, Escherichia coli as an example for Gram-negative bacteria, and Candida albicans as a representative of fungi. The minimum inhibitory concentration (MIC) was determined for test compounds as well as for reference standards. Among the compounds tested, compounds having nitro substituents at the arylidene moiety showed the most potent antifungal as well as antibacterial activities against E. coli. Compound 23 displayed an antifungal activity comparable to that of nystatin. However, none of the compounds demonstrated any antibacterial activity against S. aureus. Hydrophobicity of the target compounds correlated weakly with their antibacterial and antifungal activities. The most potent compounds namely, 7, 18, 19, 22, and 23 were assessed for hemolytic toxicity and found to be non-hemolytic up to a concentration of 100mug/mL. In addition, the most potent compound (23) was evaluated for in vitro cytotoxic activity against various cancer cell lines. This compound was found to display no cytotoxic activity but rather it induces the proliferation rate of Hep-G2 cells.

Anti-Bacterial Agents↗
PubMed2002

Liver dysfunction among workers handling 5-nitro-o-toluidine.

BACKGROUND: 5-Nitro-o-toluidine is an aromatic nitro amino compound. While other aromatic compounds are known to damage the human liver and are registered as toxic substances, toxicity information concerning 5-nitro-o-toluidine is lacking. AIMS: To investigate the hepatotoxicity of 5-nitro-o-toluidine. PATIENTS AND METHODS: Of 15 workers in the same factory who handled 5-nitro-o-toluidine, three were hospitalised with symptoms of acute liver dysfunction. Suspecting a link between liver dysfunction and working conditions, we correlated workplace factors with clinical findings in all 15 workers. RESULTS: Blood biochemistry tests indicated liver damage in seven of 15 study subjects. Workers who handled 5-nitro-o-toluidine and nitrosyl sulphuric acid often loosened their respiratory protective equipment shortly after 5-nitro-o-toluidine powder had been dispersed into the air of the room. No potential hepatotoxins were present except for 5-nitro-o-toluidine. Six of the affected workers had handled 5-nitro-o-toluidine 12 to 20 times; the seventh worker had handled the powder three times; and the other eight workers without liver dysfunction had handled the material once or twice. No other significant differences in background were evident between the affected and unaffected workers, such as age, sex, or protective measures. Histological findings during recovery from liver damage were similar to those of acute viral hepatitis. None of the 15 subjects has demonstrated liver damage since the factory was closed. CONCLUSIONS: A link between liver dysfunction and 5-nitro-o-toluidine exposure is suggested by greater severity of liver dysfunction associated with more episodes of handling.

Acute Disease↗