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PubMed1982

Syntheses of 4-[N-(tert-butoxycarbonyl)aminoacyloxymethyl]-3-nitrobenzoic acids for use in the liquid-phase peptide synthesis.

The syntheses of 4-(Boc-aminoacyloxymethyl)-3-nitrobenzoic acids are described. These compounds are suitable reagents for coupling to polyethylene glycol or its derivatives by the dicyclohexylcarbodiimide method to obtain 4-(Boc-aminoacyloxymethyl)-3-nitrobenzoyl-polyethylene glycol support. This is demonstrated by the reaction of the 4-carboxy-2-nitrobenzyl ester of Boc-alanine with glycylpolyethylene glycol in excellent yield. This synthetic route produces a much better coupling yield and an easier purification procedure in comparison with the original method in which Boc-amino acid cesium salts are allowed to react with 4-(bromomethyl)-3-nitrobenzoyl-polyethylene glycol.

Amino Acids↗

PubMedDate not supplied

Transient activation of the Ca2+-ATPase from sarcoplasmic reticulum during thiol modification by 5,5'-dithiobis(2-nitrobenzoate).

In the reaction of sarcoplasmic reticulum membranes with excess 5,5'-dithiobis(2-nitrobenzoate) (DTNB) some new features were observed: The Ca2+-dependent ATPase activities of increasingly modified preparations were considerably enhanced during the initial stage of thiol blockage. A maximum (130-160% of the control activity) was reached when about 1.5-2 mol thiol groups per 10(5) g vesicular protein had reacted, in the absence of ATP and detergent. At higher extents of modification inactivation occurred. Purified ATPase behaved principally similar to native sarcoplasmic vesicles. In the presence of Mg2+ and ATP the activity maximum (up to 180% of control) was broadened and shifted towards a higher degree of thiol blockage. Concomitantly the modification and inactivation rates were considerably reduced. Glycerol (10-30%, v/v) slightly enhanced the ATPase activity maximum and reduced the rate of inactivation essentially only by decreasing the DTNB modification rate. In the presence of sufficient myristoylglycerophosphocholine for solubilization no activation was observed. The steady state level of phosphoprotein from ATP was raised to about 150% of the control level 10 s after addition of DTNB (about 1/2 thiol blocked), followed by a linear decrease with the number of thiols labeled, while the Ca2+-dependent ATPase activity of preparations modified under equivalent conditions (10(-4) M Ca2+ and 2 X 10(-3) M Mg2+ present) showed a broader maximum corresponding to 1.5 thiols blocked.

Adenosine Triphosphate↗

PubMed1975

4-Nitrobenzoic acid reductase of Ascaris lumbricoides var suum. Substrate specificity and reaction products.

1. The substrate specificity of nitro-reductase from Ascaris lumbricoides varsum was determined. This enzyme reduced nitrobenzene, 4-nitrohippuric acid and the isomers of nitrophenol, nitroanisole, nitrobenzoic acid, nitrobenzaldehyde and nitrobenzyl alcohol. The same enzyme preparation reduced azobenzene, 4-dimethylaminoazobenzene and 1,2-dimethyl-4-(4-carboxyphenylazo)-5-hydroxybenzene. Nitrobenzaldehyde isomers were not reduced to the alcohols. 2. The products of nitro- and azo-reduction were the corresponding amines, no hydroxylamino or hydrazo compounds were detected. 3. The pH optima and cofactor requirements were the same for both azo- and nitro-reduction and neither reaction was inhibited by oxygen. 4. Ammonium sulphate fractionation failed to separate azo- and nitro-reductase activities. The molecular weight of both azo- and nitro-reductase was about 130 000.

Amines↗

PubMed1999

[Analysis of HPLC of isomers of nitrotoluene and nitrobenzoic acid].

Nitrotoluene and nitrobenzoic acid isomers were separated completely in less than 10 minutes by Kromasil C18 (200 mm x 4.6 mm i.d.), when V(CH3OH):V(H2O):V(THF) = 55:44:1 with beta-CD of 0.02 mol/L at flow rate of 2.0 mL/min (former 4 min) and 2.6 mL/min (later 6 min). Detector of UV-254 at 0.04 AUFS was used.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

[Effect of nitrobenzoic acid on methemoglobin content in blood and activity of antioxidative enzymes in erythrocytes].

Intraperitoneal administration of meta-nitrobenzoic, 3,5-dinitrobenzoic, 2,4,6-trinitrobenzoic and 3,5-dinitro-4-methylbenzoic acids to the white mice in a dose equal to LD50 has induced an increase in the methaemoglobin content in their blood. Total activity of dehydrogenases of pentosephosphate pathway, content of 2,3-diphosphoglycerate increase in response to the intoxication evoked by the mentioned acids. The acute intoxication does not practically change the activity of the key enzymes of antioxidant protection: superoxide-dismutase, catalase and glutathione peroxidase.

2,3-Diphosphoglycerate↗

PubMed2005

Evaluation of a rapid differentiation test for the Mycobacterium tuberculosis complex by selective inhibition with rho-nitrobenzoic acid and thiophene-2-carboxylic acid hydrazide.

SETTING: Mycobacterial growth in media to which inhibitory substances are added has been used in species identification. Growth of the Mycobacterium tuberculosis complex (MTC) is inhibited by rho-nitrobenzoic acid (PNB), whereas non-tuberculous mycobacteria (NTM) are resistant. Thiophene-2-carboxylic acid hydrazide (TCH) is useful in the differentiation of MTC when performed together with other tests. OBJECTIVE: To develop a test using PNB or TCH added to culture medium, and to evaluate its usefulness in the screening of mycobacteria isolates. DESIGN: In 2001, PNB testing was performed in 109 M. tuberculosis strains identified by Instituto Adolfo Lutz (IAL) and 52 NTM strains from the institute's culture collection. The drugs were added to Löwenstein-Jensen (LJ) medium and to BBL-MGIT. RESULTS: Species differentiation of MTC with the MGIT/TCH method was similar to that observed using the conventional LJ/TCH method. The accuracy of the MGIT/PNB method to differentiate NTM and MTC strains was 99.4%. The BBL-MGIT system allowed presumptive identification in 3-11 days, compared to > or =12 days with LJ medium. CONCLUSION: A simple, low-cost test using growth inhibitors may be incorporated into a modern, safe and quick methodology enabling differentiation of MTC and NTM.

Bacteriological Techniques↗

PubMed1990

[Reactions of 1-(X-benzoyl)-4-R-thiosemicarbazide with chloroacetone and omega-bromoacetophenone. II. 4-Phenyl- and 4-(p-tolyl)-thiosemicarbazide of p-nitrobenzoic acid].

The reactions of 4-phenyl- and 4-(p-tolyl)-thiosemicarbazide of p-nitrobenzoic acid (Ic, d) with chloroacetone and omega-bromoacetophenone were investigated in: 1) methanolic medium (method D); 2) methanolic medium in the presence of anhydrous CH3COONa (method E); 3) methanolic medium in the presence of N(C2H5)3 (method F). The properties of compounds IIe-h and IIIe-h were determined under the conditions of basic and acidic hydrolysis. The results of UV and IR spectroscopic measurements were reported.

Acetone↗

PubMed1990

[Reactions of 1-(X-benzoyl)-4-R-thiosemicarbazide with chloroacetone and omega-bromoacetophenone. III. 4-Phenyl- and 4-(p-tolyl)- thiosemicarbazide of 0-nitrobenzoic acid].

Reactions of 4-phenyl- and 4-(p-tolyl)-thiosemicarbazide of o-nitrobenzoic acid (Ie-f) with chloroacetone and omega-bromoacetophenone were investigated in: 1) methanolic medium (method D); 2) methanolic medium in the presence of anhydrous CH3COONa (method E); 3) methanolic medium in the presence of N(C2H5)3 (method F.). The properties of compounds IIi-1 and IIIi-1 were determined under the conditions of basic and acidic hydrolysis. The results of UV and IR spectroscopic measurements as well as those of in vitro investigations were reported. The formation of the mixture of isomeric compounds II and III (Parts I-III) takes place also in the reaction of 4-R-thiosemicarbazides of acids stronger than benzoic (Ia-f) in methanol (method D). This may be clarified basing on the pKa value for the reaction: R1-CO-NH-NH2 + H+<-->R1CO-NH-NH3+ for the proper hydrazides (R1 = C6H5; p-Cl-C6H4; p-O2N-C6H4; o-O2N-C6H4).

Acetone↗

PubMed1978

[Accessibility of sulfhydryl groups to 5,5'-dithiobis-2-nitrobenzoic acid and acid-base properties of bovine and walleye pollock rhodopsin preparations].

Both the number of exposed SH-groups and the rate of reaction with 5,5'dithiobis-2-nitrobenzoic acid (DTNB) in walleye pollock and bovine rhodopsin depend on a degree of native structure of the preparation to be investigated. The preparations studied can be arranged in the order of increase of these parameters as follows: ROS less than rhodopsin extracted by digitonin less than triton X-100 less than cetyltrimethylammonium bromide (CTAB) less than sodium dodecylsulphate (SDS). After illumination of ROS and digitonin, triton X-100 and CTAB-solubilized rhodopsin, and increase was observed in the number of modified SH-groups. Dark and bleached samples of walleye pollock rhodopsin exhibited a faster rate reaction and a more number of modified SH-groups as compared to bovine preparation. The differences between bovine and walleye pollock preparation disappeared after complete opsin unfolding as a result ROS solubilization in SDS. Six SH-groups per molecule of rhodopsin were modified in both preparation under these conditions. No differences in the number of cysteine residues (10--11), disulfide groups (2), acid (35--40) and base (25--30) titratable groups per rhodopsin molecule were found between bovine and walleye pollock ROS membranes. The isoelectric point of both rhodopsin preparations was within the pH range 5.2--5.6. After proteolysis of ROS with papain, a fragment with molecular weight 24500 +/- 1000 was detected, which contained the same number of SH-groups and cysteine residues as in the case of intact rhodopsin. The results obtained suggest that, in spite of a similar primary structure, the walleye pollock visual pigment has more "loose" and "fluid" space packing in the ROS membrane than the bovine pigment.

Animals↗

PubMed1988

Enhancement of insulin binding to rat white adipocytes at 15 degrees C by 5,5'-dithiobis-(2-nitrobenzoic acid). Independence of the reagent's sulfhydryl group reactivity.

Insulin binding to isolated rat white adipocytes at 15 degrees C, a temperature at which cellular degradation of insulin is negligible, has been found to be described by the Two-step Binding Model: R + I in equilibrium RI in equilibrium R'I (Lipkin, E. W., Teller, D. C., and de Haën, C. (1986) J. Biol. Chem. 261, 1702-1711). RI is the initially formed complex between the receptor, R, and insulin, I, and R'I is the complex in an altered state or cellular location. Here the possibility was examined that R'I results from disulfide exchange between the receptor and insulin, an exchange proposed by Clark and Harrison (Clarke, S., and Harrison, L. C. (1986) J. Biol. Chem. 257, 12239-12244) to occur at 37 degrees C. A number of sulfhydryl reagents representing various chemical reactivities did not affect insulin binding. The exception was 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), which enhanced the number of insulin-binding sites up to 2-fold with no effect on the equilibrium constant. The data suggested that this enhancement was due to activation of cryptic binding sites pre-existing on the cell surface, possibly by increasing the valency of the receptor from 1 to 2. Insulin binding was also enhanced by structural congeners of DTNB devoid of sulfhydryl reactivity, the simplest one being benzoic acid. It was concluded that the effects were not related to modification of sulfhydryl groups, that modification of sulfhydryl groups on the receptor either did not take place or was without effect on binding, and finally, that disulfide exchange between insulin and the receptor was an unlikely explanation for the formation of R'I. Also, since it is possible to show insulin action at 15 degrees C, contrary to the proposal by Clark and Harrison (Clark, S., and Harrison, L. C. (1983) J. Biol. Chem. 258, 11434-11437), disulfide exchange does not appear to be necessary for signal transmission by the occupied receptor.

Adipose Tissue↗

PubMed1987

Effect of daylight on the reaction of thiols with Ellman's reagent, 5,5'-dithiobis(2-nitrobenzoic acid).

The reaction of 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB, Ellman's reagent) with thiols is sensitive to daylight, in particular to ultraviolet radiation at wavelengths around 325 nm. Exposure to light at the absorbance maximum of the yellow product (the thionitrobenzoate ion) at 410 nm had no effect on the reaction. The light-sensitive species is apparently the DTNB, because a spectral-irradiation experiment showed that the wavelength of light that produced the maximum rate of absorbance change coincided with the peak absorbance of DTNB, and it was well separated from the thionitrobenzoate absorbance peak. Ascorbate is ineffective as a stabilizer and can produce an apparent increase in the rate of DTNB destruction. In a practical example we found the light interference to be severe when hydrolysis of propionylthiocholine by plasma cholinesterase (EC 3.1.1.8) was measured after a 20-min incubation. The apparent cholinesterase activity in clear glass or plastic tubes exposed to diffuse daylight could be decreased to 25% of the value obtained for samples in light-excluded tubes. We recommend the reaction be carried out in artificial room light, with total elimination of daylight, because window glass does not sufficiently attenuate 325-nm wavelength irradiation.

Cholinesterases↗

PubMedDate not supplied

Enhancement of reductive metabolism of p-nitrobenzoate and nitrazepam in isolated perfused rat liver by ethanol.

Reductive metabolism of p-nitrobenzoate (2 mM) was studied in the isolated perfused rat liver, after acute ethanol dosing, with use of a hemoglobin-free perfusion medium. Formation of reduced metabolites under control conditions (0.3 mumol per g of liver per hr) was enhanced fivefold (1.4 mumol/g/hr) in the presence of ethanol (38 mM), thus reaching hepatic reductase activities occurring under anaerobic conditions (1.4 mumol/g/hr). Ethanol failed to increase hepatic nitro reduction when alcohol dehydrogenase was inhibited by pyrazole. Addition of acetaldehyde led to a marked stimulation of nitroreductase activity. Carbon monoxide did not influence the ethanol-mediated enhancement of nitroreductase activity but almost abolished the enhancement caused by anoxia. Reductive azo cleavage of salazosulfamide was not enhanced by ethanol. When nitrazepam was used as the substrate (1 mM) for the isolated perfused rat liver, addition of ethanol (38 mM) led to an enhanced content of 7-amino derivative in the liver and in the perfusate, whereas the formation of 7-acetylamino derivative remained unchanged. The distribution of nitrazepam in liver and perfusate was not altered by ethanol.

Animals↗

PubMed1985

Studies on the reactivity of the essential sulfhydryl groups as a conformational probe for the fatty acid synthetase of chicken liver. Inactivation by 5,5'-dithiobis-(2-nitrobenzoic acid) and intersubunit cross-linking of the inactivated enzyme.

Fatty acid synthetase of chicken liver is rapidly and reversibly inactivated by 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) at a rate (k2 = 132 mM-1 S-1 in 3 mM EDTA, 1% (v/v) glycerol, pH 7.0, at 25 degrees C) up to 2200 times higher than the reaction of this reagent with simple thiol compounds. The inactivation is caused by the reaction of the phosphopantetheine SH group, since it is protected competitively by either acetyl- or malonyl-CoA, and since the inactivated enzyme is unreactive with the phosphopantetheine label chloroacetyl-CoA but reactive with the cysteine reagent 1,3-dibromopropanone. Moreover, chloroacetyl-CoA prevents the modification of the rapidly reacting essential SH group by DTNB. The number of SH groups involved in inactivation was determined by correlating activity loss with the extent of reaction and by stopped-flow analysis of substrate (or chloroacetyl-CoA) protection. Values between 0.91 and 1.15 SH groups/dimer were obtained, indicating the presence of substoichiometric amounts of the prosthetic group in the fatty acid synthetase preparations used in this study. Inactivation of the synthetase by DTNB is strongly inhibited by increasing salt concentration and protected noncompetitively by NADP+ and NADPH. Treatment of the enzyme inactivated at low salt by salt, NADP+, or NADPH also effectively reduced cross-linking between enzyme subunits. The parallel effects of these treatments on the reaction with DTNB and subsequent dimerization are consistent with a minimum model of two discreet conformation states for fatty acid synthetase. In the low salt conformer, the phosphopantetheine and cysteine SH groups are juxtaposed, and the DTNB reaction (k2 approximately 132 mM-1 S-1) and dimerization are both facilitated. Transition to the high salt conformer by the above treatments is accompanied by an approximately 20-fold reduction of reactivity with DTNB (k2 = 6.8 mM-1 S-1) and reduced dimerization, due to spatial separation of the SH groups. During palmitate synthesis, the enzyme may oscillate between these conformation states to permit the reaction of intermediates at different active sites. Results obtained by studies on the effect of pH on DTNB inactivation implicate a pK of 5.9-6.1 for the essential SH group independent of salt concentration. This value is 1.5-1.8 pH units lower than the pK of 7.6-7.7 for CoA and may explain the 23-fold increase of the rate constant from a value of 0.3 mM-1 S-1 for CoA to that of the high salt conformer.

Animals↗

PubMed1996

[Reactions of 1-(X-benzoyl)-4-R-thiosemicarbazide with chloroacetone and omega-bromoacetophenone. VI. 4-(o-tolyl)-thiosemicarbazide of o-nitro - and p-nitrobenzoic acid].

The reactions of 4-(o-tolyl)-thiosemicarbazide of o-nitro- and p-nitrobenzoic acid (Ik, l) with chloroacetone and omega-bromoacetophenone were investigated in: methanolic medium (method D); methanolic medium in the presence of anhydrous CH3COONa (method E); methanolic medium in the presence of N(C2H5)3 (method F). The properties of compounds IIu-y and IIIu-y were determined under the conditions of basic and acidic hydrolysis. The results of UV, IR and NMR spectroscopic measurements were reported.

Acetone↗

PubMed1998

Dynamic modeling of meta- and para-nitrobenzoate metabolism by a mixed co-immobilized culture of comamonas spp. JS46 and JS47

A model describing the transient activity of a mixed immobilized culture of Comamonas spp. JS46 and JS47 growing on mixed substrates is presented. The transient periods considered are those following changes in the feed carbon source, which alternated between meta- and para-nitrobenzoate. The feed profile alternately starved one of the species in the mixed culture. The response of the system, as quantified by the reactor effluent substrate concentrations, is dictated by the activity of the biomass and the appropriate biochemical pathway. As detailed mechanistic pathway information is not available, respirometry has been used to characterize both facets of activity. Two parameters were introduced: Psi representing pathway activity and Gamma representing biomass activity; a detailed description of the analysis is included. The model is compared to experimental investigation of the system and describes the reactor response well. The agreement between model and experiment suggests the usefulness of oxygen kinetics as global measurements to describe complex systems when mechanistic detail is not available. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗

PubMed1987

HPLC electrochemical fluorometric detection of amino acids including tryptophan using 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole.

It has been shown that by electrochemical oxidation 7-nitrobenzo-2-oxa-1,3-diazole-tryptophan (NBD-T) is converted to fluorophores having the same emission and excitation spectra as those for other NBD-amino acids. NBD-dioxindolylalanine was tentatively assumed to be a main electrochemical oxidation product of NBD-tryptophan. A coulochemical cell placed between an analytical column and a fluorometer showed no detrimental effect on the separation of NBD-amino acids by reversed phase HPLC. Highly sensitive fluorescence detection was achieved for amino and imino acids at 10-100 fmol levels. The detection limit for tryptophan was 50 fmol.

4-Chloro-7-nitrobenzofurazan↗

PubMedDate not supplied

A sensitive detection method for peptide using 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole and its application to measure prolyl endopeptidase activity.

A measuring method sensitive to prolyl endopeptidase (EC 3.4.21.26, PEP) activity using native peptides (Arg-vasopressin or substance P) as substrates was established. The investigation of three different derivatization reagents, which had been developed for an amino acid analysis, demonstrated that 4-fluoro-7-nitrobenzo-2-oxa-1,3-diazole (NBDF) was the most suitable for the detection of Arg-Gly-NH2, which was released from Arg-vasopressin by PEP. Arg-Gly-NH2 was reacted with NBDF at 65 degrees C for 5 min at pH 7.6 and the reaction mixture was analysed by HPLC on a reverse-phase column by monitoring the fluorescence intensity. The detection limit was 1 picomol per injection and the linear standard calibration curve could be constructed in the range of 1 to 100 picomol per injection with a 3.0% relative standard deviation. This sensitive detection method for peptide was applied to the measurement of PEP activity using Arg-vasopressin as a substrate and 1 x 10(-3) unit of PEP activity was detectable. This method was also applicable to the measurement of PEP activity using substance P as a substrate by detecting the derivative of its fragment peptide (Arg-Pro-Lys-Pro).

4-Chloro-7-nitrobenzofurazan↗

PubMed1992

Nitrobenzo[a]pyrene-induced DNA amplification in SV40-transformed Chinese hamster embryo cells.

Nitrobenzo[a]pyrenes (NBaPs) are ubiquitous environmental pollutants that produce mutations in Salmonella typhimurium and Chinese hamster ovary cells. In this study, 1-, 3-, and 6-NBaP induced amplification of SV40 DNA sequences in an SV40-transformed Chinese hamster embryo cell line which is sensitive to DNA amplification by various known carcinogens. Of the three isomers, 3-NBaP produced the highest level of gene amplification, which was 4.8 relative to untreated controls at a dose of 5 micrograms/ml. Considering the relationship between gene amplification and tumorigenesis, it seems prudent to carry out a more exhaustive analysis of the carcinogenic potential of these agents.

Animals↗