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PubMed1995

Bacterial degradation of m-nitrobenzoic acid.

Pseudomonas sp. strain JS51 grows on m-nitrobenzoate (m-NBA) with stoichiometric release of nitrite. m-NBA-grown cells oxidized m-NBA and protocatechuate but not 3-hydroxybenzoate, 4-hydroxy-3-nitrobenzoate, 4-nitrocatechol, and 1,2,4-benzenetriol. Protocatechuate accumulated transiently when succinate-grown cells were transferred to media containing m-NBA. Respirometric experiments indicated that the conversion of m-NBA to protocatechuate required 1 mol of oxygen per mol of substrate. Conversions conducted in the presence of 18O2 showed the incorporation of both atoms of molecular oxygen into protocatechuate. Extracts of m-NBA-grown cells cleaved protocatechuate to 2-hydroxy-4-carboxymuconic semialdehyde. These results provide rigorous proof that m-NBA is initially oxidized by a dioxygenase to produce protocatechuate which is further degraded by a 4,5-dioxygenase.

Biodegradation, Environmental↗
PubMed2006

The locus coding for the 3-nitrobenzoate dioxygenase of Comamonas sp. strain JS46 is flanked by IS1071 elements and is subject to deletion and inversion events.

In Comamonas sp. strain JS46, 3-nitrobenzoate (3Nba) is initially oxidized at the 3,4 position by a dioxygenase, which results in release of nitrite and production of protocatechuate. The locus coding for the 3Nba dioxygenase (designated mnb, for m-nitrobenzoate) was mobilized from strain JS46 using a plasmid capture method, cloned, and sequenced. The 3Nba dioxygenase (MnbA) is a member of the phthalate family of aromatic oxygenases. An open reading frame designated mnbB that codes for an NAD(P)H-dependent class IA aromatic oxidoreductase is downstream of mnbA. MnbB is tentatively identified as the oxidoreductase that transfers reducing equivalents to MnbA in strain JS46. The mnb locus is flanked by IS1071 elements. The upstream element is interrupted by a novel insertion sequence designated ISCsp1, and the transposase genes of the flanking insertion elements are transcribed in the direction opposite the direction of mnbA transcription. Spontaneous deletion of mnb occurs because of homologous recombination between the directly repeated flanking IS1071 elements. In addition, in approximately 0.007 to 0.2% of any population of JS46 cells growing on 3Nba, alternative orientations of mnb relative to the flanking IS1071 elements are detected. These alternative forms are the result of inversions of mnb and the flanking IS1071 elements. Inversions appear to occur because of homologous recombination between the inverted repeats that flank the IS1071 elements.

Bacterial Proteins↗
PubMed1975

4-Nitrobenzoic acid reductase of the nematode Ascaris lumbricoides var suum. Localization of the enzyme and optimum assay conditions.

1. Reduction of 4-nitrobenzoic acid by the nematode Ascaris lumbricoides var suum occurred in the intestinal brush border cells. Cuticle, mesenchyme fluid and reproductive tissue showed no activity. 2. 4-Nitrobenzoic acid reductase was in the supernatant fraction after centrifugation of intestinal homogenates at 75 000 g for 2 h. 3. The enzyme required as cofactors NADH2, a low molecular weight thiol such as glutathione or cysteine and a divalent metal ion such as Mn++ or Cu++. The reduction was not catalysed by NADPH2. 4. Reduction was not inhibited by O2 or CO. Optimum pH of the reaction was about 6.5.

Animals↗
PubMed1978

Gas-liquid chromatographic determination of sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate residues on soybeans and foliage, soil, milk, and liver.

Residues of sodium 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate and its free acid are determined by treating a sample extract with diazomethane to convert the residues to methyl 5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoate. This compound is purified by chromatography on Florisil and measured by electron capture gas-liquid chromatography. The method has been used on soybeans, soybean foliage, soil, milk, and liver. It can detect 0.01 ppm with recoveries of 70--75%.

Animals↗
PubMed1998

Operation of mixed-culture immobilized cell reactors for the metabolism of meta- and para-nitrobenzoate by comamonas sp. JS46 and comamonas sp. JS47

The treatment of meta- and para-nitrobenzoic acid in an industrial wastestream by Comamonas sp. JS46 and Comamonas sp. JS47 is investigated. The most important feature of the wastestream is the constantly changing concentration ratio of the two isomers. The most extreme occurrence is considered here: the complete change in feed carbon source from one isomer to the other. A series of immobilized cell airlift reactor experiments are described to examine the operation and response of the system to these changes in the feed carbon source. Separate reactors containing each species immobilized are compared with a reactor containing both species immobilized within the same bead, and to a reactor containing both species with each species confined to separate beads. On the basis of response time necessary to recover the appropriate activity, the reactor containing both species immobilized within the same bead offers the most effective arrangement. Interactions occurring between the two organisms in the coimmobilized system, mediated by the nitrobenzoate metabolites, are discussed relative to the improved response of this arrangement. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗
PubMed1993

Hemoglobins with multiple reactive sulphydryl groups: the reaction of pigeon hemoglobin with 5,5'-dithiobis (2-nitrobenzoic acid).

Pigeon hemoglobin has eight reactive sulphydryl groups per (tetramer) molecule, as determined by Boyer titration with p-chloromercuribenzoate. However, only four of these are titratable with 5,5'-dithiobis(2-nitrobenzoate) under the same experimental conditions. The time course of the reaction of pigeon hemoglobin with 5,5'-dithiobis(2-nitrobenzoate) is biphasic. In the pH range 6-9, the fast phase is between one and two orders of magnitude faster than the slow phase. For the fast phase, kapp, the apparent second-order rate constant, increases monotonously with pH. Quantitative analysis reveals that the reaction of the sulphydryl group responsible for this phase is coupled to the ionization of two groups with pKa values of 6.15 +/- 0.1 and 8.5 +/- 0.1. These pKa values are assigned to HisHC3(146) beta and to the CysF9(93) beta sulphydryl group, respectively. For the slow phase the kapp vs. pH profiles are bowl-shaped. Analysis reveals that the reaction of the sulphydryl group to which this phase may be attributed is coupled to the ionization of two groups with mean pKa values of 6.53 +/- 0.1 and 8.25 +/- 0.1. Examination of the structure of hemoglobin allows us to assign these values to HisG19(117) beta and CysB5(23) beta, respectively. The CysB5(23) beta sulphydryl is in the region of the molecule where amino acid substitutions have been found to give rise to significant changes in the oxygen affinity of hemoglobin [Huang et al. (1990), Biochemistry 29, 7020-7023].

Amino Acid Sequence↗
PubMed2007

Determination of five nitrobenzoic acids in groundwater by solid-phase extraction and liquid chromatography-mass spectrometry.

A method involving solid-phase extraction (SPE) and reversed-phase liquid chromatography-mass spectrometry (LC-MS) has been developed for determination, in groundwater, of nitrobenzoic acids associated with 2,4,6-trinitrotoluene production. Pre-concentration on a co-polymer-based SPE cartridge enabled quantitative extraction of the analytes from water. Investigation of negative ion electrospray and atmospheric-pressure chemical ionization mass spectrometry indicated the sensitivity of APCI was more than twice that of ESI. An 15N-labeled internal standard was used to achieve more accurate quantitation and mass assignment. Recovery was better than 80% when 10 mL water was extracted with the SPE cartridge. Combination of SPE with LC-MS analysis resulted in method detection limits of less than 5 microg L-1. The method has been used for analysis of groundwater samples collected from a site of a former ammunition plant. Contamination with nitrobenzoic acids was determined at microg L-1 levels.

Journal Article↗
PubMedDate not supplied

Nitroreduction of 6-nitrobenzo[a]pyrene: a potential activation pathway in humans.

6-Nitrobenzo[a]pyrene, an environmental pollutant, was metabolized by human intestinal microflora to 6-nitrosobenzo[a]pyrene and 6-aminobenzo[a]pyrene. The two-electron reduction product 6-nitrosobenzo[a]pyrene exhibited strong direct-acting mutagenicity in the Salmonella typhimurium assay. These results imply that 6-nitrobenzo[a]pyrene can be hazardous to human health via a nitroreduction activation pathway and opens the possibility that other nitro-polycyclic aromatic hydrocarbons that are not direct-acting mutagens may be activated in vivo by a similar mechanism.

Benzopyrenes↗
PubMed1999

Use of 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole for determining cysteine and cystine in cereal and legume seeds.

A new colorimetric method has been developed for the determination of chemically available cysteine and half-cystine in maize and legume seeds. The method is based on the reduction of cystine with aqueous NaBH(4)/urea/EDTA solution and the reaction of cysteine with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in 0.2 M sodium acetate/HCl buffer (pH 2.0) to form a greenish product showing maximum absorbance at 410 nm. The method is simple, accurate, and highly specific for cysteine, in the presence of other naturally occurring amino acids. The method was applied to the determination of cysteine and of cysteine plus half-cystine in some seed meals. There was a good correlation between the results obtained using this method and those obtained using Ellman's reagent [5, 5-dithiobis(2-nitrobenzoic acid)]. There was also a good correlation between the results obtained using this method and cysteic acid values calculated from amino acid analysis of the samples.

4-Chloro-7-nitrobenzofurazan↗
PubMedDate not supplied

Nitroreduction of 1- and 3-nitro-7,8,9,10-tetrahydrobenzo[a]pyrene and 1-nitrobenzo[a]pyrene resulting in formation of N2-deoxyguanosinyl adducts through long-range migration.

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.

Animals↗
PubMed1975

A reporter group delivery system with both absolute and selective specificity for thiol groups and an improved fluorescent probe containing the 7-nitrobenzo-2-oxa-1,3-diazole moiety.

1. 4-(N-2-Aminoethyl2'-pyridyl disulphide)-7-nitrobenzo-2-oxa-1,3-diazole (compound I) was synthesized and evaluated as a fluorescent labelling reagent for thiol groups. 2. The design of compound (I) as one example of a general type of reporter group delivery reagent (2-pyridyl-S-S-X, where X contains an environmentally sensitive spectroscopic probe) is discussed. 3. The electronic absorption spectrum of compound (I) was determined over a wide range of pH and the spectral changes that accompany its reaction with low-molecular-weight thiols, e.g. L-cysteine, and with papain (EC 3.4.22.2) and bovine serum albumin are discussed. 4. A new value of epsilon343 for 2-thiopyridone (Py-2-SH) was determined as 8.08 X 10(3) +/- 0.08 X 10(3)M-1-cm-1. 5. Spectral analysis of the reactions of compound (I) with L-cysteine and with papain (in the pH range 3.5-8.0) showed that even under equimolar conditions the reaction (thiol-disulphide interchange to release Py-2-SH) is essentially stoicheimoetric and probably proceeds by specific attack at the sulphur atom distal from the pyridyl ring of compound (I). 6. The fluorescence-emission spectra of compound (I) and of the products of its reaction with papain and with ficin (EC 3.4.22.3) were determined. Compound (I) is highly fluorescent in aqueous solution. Excitation within the intense visible absorption band (lambda max. 481 nm, epsilon max. 2.52 X 10(4)M-1-cm-1) provides green fluorescence with an emission maximum at 540 nm. Both papain and ficin labelled by reaction with compound (I) are characterized by fluorescence-emission maxima (535 nm and 530 nm respectively) of even higher intensity. The fluorescence emission of the product of the reaction of papain with compound (I) was shown to be 25 times more intense than that of the product of the reaction of papain with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (Nbd chloride). 7. The second-order rate constants (k2) for the reactions of compound (I) and of Nbd chloride with GSH, papain, albumin, ficin, 2-benzimidazolylmethanethiol and 2-benzimidazolylethanethiol were determined at 25.0 degrees C and various pH values. At pH4 the values of k2(compound I)/k2(Nbd chloride) are: GSH, 288; albumin, 36; papain 3 X 10(3); ficin, 3 X 10(4). 8. The pH-k2 profiles for the reactions of compound (I) and of Nbd chloride with the two 2-benzimidazolylalkanethiols were determined. Of the four profiles only that for the reaction of compound (I) with 2-benzimidazolylmethanethiol is characterized by a striking rate maximum in acidic media.

Benzimidazoles↗
PubMed1990

The induction of aneuploidy by 3-nitrobenzo[a]pyrene in Chinese hamster ovary cells.

Nitrobenzo[a]pyrenes are found in urban air particulates and particulates from diesel exhaust, gasoline engines and wood burning stoves. Following exposure of Chinese hamster ovary cells (CHO-K1-BH4) to 3-nitrobenzo[a]pyrene (3-NB[a]P), cells with multiple nuclei and/or nuclei with multiple lobes were observed. When CHO cells were treated with 5 micrograms/ml 3-NB[a]P for 5 or 20 h, aneuploidy was noted in these cells at 24-96 h post-exposure. The addition of N6, O2'-dibutyryl adenosine 3':5'-cyclic monophosphate to 3-NB[a]P-exposed CHO cell cultures appeared to reduce the amount of aneuploidy in treated cultures. Structure--activity studies showed that 1-NB[a]P was a much less effective inducer of aneuploidy than 3-NB[a]P and 6-NB[a]P was ineffective. 1-, 3- and 6-nitrosobenzo[a]pyrenes were not effective inducers of aneuploidy in CHO cells, and aneuploidy was not observed in cultures treated with 3-NB[a]P in the presence of S9 activation. It appears that the parent 3-NB[a]P is responsible for producing aneuploidy in CHO cells.

Aneuploidy↗
PubMed1990

Conformational changes of tarantula (Eurypelma californicum) haemocyanin detected with a fluorescent probe, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole.

Different fluorescent labels were tested in order to monitor conformational transitions of the four-hexamer haemocyanin from the tarantula Eurypelma californicum during the oxygenation process. When the four-hexamer was labelled with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, the maximum wavelength lambda max of the fluorescence emission spectrum was significantly shifted up to 5 nm, depending on pH and the degree of oxygenation. The values for lambda max of the fully oxygenated haemocyanin were 531.5 nm (pH less than 7.8) and 530.0 nm (pH greater than 7.8). For deoxygenated haemocyanin the values were 533.5 nm (pH less than 7.2) and 535.2 nm (pH greater than 7.2). The occurrence of four distinct emission maxima supports the hypothesis of four conformational species for the tarantula haemocyanin, which have been predicted by the nesting model [Robert, C. H., Decker, H., Richey, B., Gill, S. J. & Wyman, J. (1987) Proc. Natl Acad. Sci. USA 84, 1891-1895]. Only four amino acids of the four-hexamer were labelled with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. They were identified as lysine 484 on the purified peptide Leu-Arg-Lys-Phe-His-Arg. This amino acid is located on the surface of the four copies of subunit d. The sharp shift of the maxima of the emission wavelengths during oxygenation indicates that the four copies of subunits d synchronously take part in the conformational switch. This points to a concerted mechanism for the conformational transitions of the tarantula haemocyanin.

4-Chloro-7-nitrobenzofurazan↗
PubMed1967

Use of thiosemicarbazone and para-nitrobenzoic acid in screening tests for anonymous mycobacteria.

In screening for anonymous mycobacteria the use of thiosemicarbazone (10mug./ml.) may give rise to false positive results. Although these can usually be overcome by further tests, additional time and effort is required, which seriously limits the value of thiosemicarbazone as a true screening agent. Para-nitrobenzoic acid (500 mug./ml.) has proved more satisfactory in our hands; no false positive results have been obtained and it has the additional advantage that strains of M. kansasii (usually thiosemicarbazone sensitive) are resistant to para-nitrobenzoic acid.

Animals↗
PubMed1992

Gas phase derivatization of ammonia with 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole and its application to urease assay.

An ammonia-specific and rapid fluorometric method for determination of ammonia and urease activity was developed. The method is designed to assay ammonia levels or urease activity for the rapid diagnosis of Helicobacter pylori infection. 4-Fluoro-7-nitrobenzo-2-oxa-1,3-diazole was used to derivatize ammonia and 4-amino-7-nitrobenzo-2-oxa-1,3-diazole was analysed by high performance liquid chromatography at an excitation wavelength of 455 nm and an emission wavelength of 520 nm. Derivatization was designed to react with ammonia gas produced in a strong alkaline pH sample. The fluorescent intensity was linear in the range of 0.1-10 mM ammonia per tube when the reaction was carried out for 15 min at 37 degrees C. Urease activity, judged as the amount of ammonia production from urea, could be measured at 25 ng per tube (S/N = 1.5) with Jack bean meal urease. Because of its rapidity, this assay is potentially superior to the current standard method in use in clinical settings.

4-Chloro-7-nitrobenzofurazan↗
PubMed1999

5,5'-Dithiobis-(2-nitrobenzoic acid) as a probe for a non-essential cysteine residue at the medium chain acyl-coenzyme A dehydrogenase binding site of the human 'electron transferring flavoprotein' (ETF).

Human 'electron transferring flavoprotein' (ETF) was inactivated by the thiol-specific reagent 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB). The kinetic profile showed the reaction followed pseudo-first-order kinetics during the initial phase of inactivation. Monitoring the release of 5-thio-2-nitrobenzoate (TNB) showed that modification of 1 cysteine residue was responsible for the loss of activity. The inactivation of ETF by DTNB could be reversed upon incubation with thiol-containing reagents. The loss of activity was prevented by the inclusion of medium chain acyl-CoA dehydrogenase (MCAD) and octanoyl-CoA. Cyanolysis of the DTNB modified-ETF with KCN led to the release of TNB accompanied presumably by the formation of the thio-cyano enzyme and with almost full recovery of activity. Conservation studies and the lack of 100% inactivation, however, suggested that this cysteine residue is not essential for the interaction with MCAD.

Acyl-CoA Dehydrogenase↗
PubMed2002

[Determination of 2-methyl-3-nitrobenzoic acid through pretreatment with diazomethane by gas chromatography].

A method for the quantitative determination of 2-methyl-3-nitrobenzoic acid by gas chromatography is described. 2-Methyl-3-nitrobenzoic acid was esterified by pretreatment with diazomethane prior to analysis. A CP-Sil-43CB capillary column(25 m x 0.32 mm i.d. x 0.2 microm), a flame ionization detector and the area normalization method were used. The average recovery was 99.81%. The RSD was 0.08% and the detection limit was 3 x 10(-11) g. The results showed that the method is practical and reliable. It was realized that the higher purity and higher boiler matter was analyzed by gas chromatography. The method can be used to monitor the purity of this type of materials. analysis of research and production. It can be used in the development of new products and in the process.

English Abstract↗
PubMed1991

Interaction of glutathione transferase from horse erythrocytes with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole.

7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity.

4-Chloro-7-nitrobenzofurazan↗