PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Nitrophenols”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1979

Radiochemical synthesis and photochemical properties of the uncoupler 2-azido-4-nitrophenol, a versatile photoaffinity labeling reagent.

2-Amino-4-nitrophenol was tritiated in an acid-catalyzed hydrogen exchange reaction. Radioactive 2-azido-4-nitrophenol with a specific radioactivity up to 21 mCi/mmol was synthesized from 2-amino-4-nitrophenol by diazotization and azide coupling. The photochemical properties of the uncoupler, 2-azido-4-nitrophenol, were studied as free solute and as ligand bound to uncoupler binding sites in bovine serum albumin and mitochondria. Based on product analyses, irradiation of free or bound 2-azido-4-nitrophenolate with visible light results in the formation of nitrene intermediates with a singlet to triplet ratio of 6:1 to 9:1. 2-Azido-4-nitrophenolate and bovine serum albumin form a strong 1:1 complex (KD = 0.7 micron) which can be converted into a photoproduct with a covalent bond between the label and the protein. The acid dissociation constant of the protein-bound 2-amino-4-nitrophenol moiety is strongly pH dependent. Photoaffinity labeling of mitochondria by 2-azido-4-nitrophenolate follows a pattern expected from equilibrium binding studies using normal and lipid-depleted particles: polypeptides were found to bear 90-95% of the radioactive label, and 5-10% of the latter was bound to phospholipids. Two polypeptides (approximately 56 000 and 31 000 daltons) were associated with 60% of the label, indicating a high degree of specific photochemical labeling.

Affinity Labels↗
PubMed1976

Metabolism of nitrophenols by bacteria isolated from parathion-amended flooded soil.

Two bacterial isolates from parathion-amended flooded soil, Pseudomonas sp. and Bacillus sp., were examined for their ability to decompose nitrophenols. Uniformly labelled 14C-p-nitrophenol was metabolized by both bacteria, 14CO2 and nitrite being end products. A substantial portion (23% for Pseudomonas sp. and 80% for Bacillus sp.) of radioactivity applied as p-nitrophenol was accounted for as 14CO2 at the end of a 72-h period; 8 to 16% remained in the water phase after solvent extraction. Pseudomonas sp. produced nitrite also from 2,4-dinitrophenol, but only after a lag, and not from o- and m-nitrophenols. Interestingly, m-nitrophenol, known for its resistance to biodegradation because of meta substitution, was decomposed by Bacillus sp., resulting in the formation of nitrite and phenol; o-nitrophenol and 2,4-dinitrophenol resisted degradation by this bacterium.

Bacillus↗
PubMed1979

[Behaviour of p-nitrophenol-glucuronide in hydrolysis with mineral acids (author's transl)].

The behaviour of p-nitrophenol and synthetic p-nitrophenol-glucuronide with mineral acids has been investigated. With sulfuric acid (33%) about 93% of the glucuronide derivative have been hydrolysed; the solution was heated in open vessel for 15 sec. With hydrochloric acid (6%) only about 65% of the conjugated p-nitrophenol have been converted to the free form. No losses were detected, when free p-nitrophenol was treated under the same conditions. Three other methods of hydrolysis have been applied.

Glucuronates↗
PubMed1977

Phenol sulphotransferase and uridine diphosphate glucuronyltransferase from rat liver in vivo and vitro. 2,6-Dichloro-4-nitrophenol as selective inhibitor of sulphation.

Microsomal UDP-glucuronyltransferase and cytosolic sulphotransferase share many substrates, such as phenols and hydroxamic acids. In a search for a selective inhibitor of sulphation, several phenolic compounds were tested. 2,6-Dichloro-4-nitrophenol is introduced as a selective inhibitor of sulphation in vivo, having no effect on UDP-glucuronyltransferase activity. As substrate for both conjugating enzymes the phenolic drug harmol (7-hydroxy-1-methyl-9H-pyrido[3,4-b]indole) was used. In the rat in vivo 2,6-dichloro-4-nitrophenol caused almost complete inhibition of harmol sulphation after a single intraperitoneal injection (26mumol/kg) for 48h; the percentage of harmol sulphated decreased from 75% in controls to 5% in the treated rats. The percentage of harmol glucuronidated increased from 25 to 95%. Pentachlorophenol was equally effective but also highly toxic. Salicylamide had only a very-short-lasting inhibitory effect on sulphation. In vitro, 2,6-dichloro-4-nitrophenol inhibited sulphation of harmol by a rat liver postmitochondrial supernatant completely at 1mum, whereas even at 100mum it had no effect on glucuronidation of harmol. It is concluded that 2,6-dichloro-4-nitrophenol is a selective inhibitor of sulphation and, further, that its long duration of action makes it suitable for studies on the regulatory role of sulphation in some biological processes.

Animals↗
PubMed1979

Inhibition of sulfation of phenols in vivo by 2,6-dichloro-4-nitrophenol: selectivity of its action in relation to other conjugations in the rat in vivo.

The effect of 2,6-dichloro-4-nitrophenol, an inhibitor of the sulfation of the phenolic compound harmol in vivo, on the sulfation of other phenolic substances and on various conjugation reactions has been studied in the rat in vivo. Compounds chemically related to 2,6-dichloro-4-nitrophenol were also tested as sulfation inhibitors. 2,6-Dichloro-4-nitrophenol inhibited the sulfation of phenol while it had no effect on biliary excretion of dibromosulphthalein, glucuronidation of phenolphthalein, acetylation of procainamide ethobromide or glutathione conjugation of ethacrynic acid. It is concluded that of these conjugation reactions sulfation is inhibited selectively at the dose level used. Some phenols with chloro- or nitro-substituents effectively inhibited the sulfation of harmol but to a lesser extent than 2,6-dichloro-4-nitrophenol. Many other phenols did not affect the conjugation of harmol, which is both glucuronidated and sulfated.

Animals↗
PubMed1975

[Detection and determination of parathion and p-nitrophenol in biological material by reverse-phase-high-power-liquid chromatography (author's transl)].

In 2 persons (female and male) who committed suicide reverse-phase-high-power-liquid chromatography (HPLC) was used to detect, in the first case, Parathion in the stomach and blood as well as p-Nitrophenol in the kidneys, and in the second case, p-Nitrophenol in the urine. The Parathion in the stomach was analyzed in quantity, directly and also after hydrolysis to p-Nitrophenol. The results were checked with gas-chromatographic and spectralphotometric methods.

Chromatography, Gas↗
PubMed1992

N.m.r. study on the formation and geometry of inclusion complexes of 6-O-(alpha-maltosyl)cyclomalto-hexaose and -heptaose with p-nitrophenol in aqueous solution.

The formation and molecular geometry of inclusion complexes of some branched cyclomaltaoses with p-nitrophenol in aqueous solution have been investigated by using high-resolution 1H-n.m.r. spectroscopy. 6-O-(alpha-Maltosyl)cyclomalto-hexaose and -heptaose were found to form 1:1 inclusion complexes with p-nitrophenol, and the dissociation constants for their complexes are quite similar to those for corresponding unbranched cyclomaltaose-p-nitrophenol complexes, indicating that formation of these inclusion complexes is not hampered by the maltosyl branch. From measurement of nuclear Overhauser enhancements, it was concluded that the maltosyl branch is not situated over the entrance of the cavity.

Carbohydrate Sequence↗
PubMed1979

Phospholipid-dependence of oestrone UDP-glucuronyltransferase and p-nitrophenol UDP-glucuronyltransferase.

Hepatic UDP-glucuronyltransferase activity was resolved into two fractions, one exhibiting oestrone glucuronyltransferase activity and the other exhibiting p-nitrophenol glucuronyltransferase activity. Hydroxyapatite-column chromatography removed greater than 95% of the phospholipids from both preparations. The partially purified delipidated enzymes were essentially devoid of catalytic activity, but activities were restored by the addition of phospholipids or phosphatidylcholine mixtures containing various saturated and unsaturated fatty acids. Both oestrone and p-nitrophenol glucuronyl-transferase activities were reconstituted to similar degrees with the phosphatidylcholine mixtures. When purified phospholipids were tested, phosphatidylcholine and lysophosphatidylcholine were most effective in restoring activity, whereas phosphatidylethanolamine was the least effective. These results further suggest that oestrone and p-nitrophenol UDP-glucuronyltransferases are dependent on phospholipids for their activity.

Animals↗
PubMed1977

4-Nitrophenol in 4-nitrophenyl phosphate, a substrate for alkaline phosphatase, as measured by paired-ion high-performance liquid chromatography.

We used paired-ion high-performance liquid chromatography to determine the 4-nitrophenol content of 4-nitrophenyl phosphate, a substrate for alkaline phosphatase analysis. This was done on a reversed-phase column with a mobile phase of methanol/water, 45/55 by vol, containing 3 ml of tetrabutylammonium phosphate reagent per 200 ml of solvent. At a flow rate of 1 ml/min, 4-nitrophenol was eluted at 9 min and monitored at 404 nm; 4-nitrophenyl phosphate was eluted at 5 min and could be monitored at 311 nm. Samples of 4-nitrophenyl phosphate obtained from several sources contained 0.3 to 7.8 mole of 4-nitrophenol per mole of 4-nitrophenyl phosphate.

4-Nitrophenylphosphatase↗
PubMed1977

Simultaneous determination of 4-nitroanisole, 4-nitrophenol, and 4-nitrocatechol by phase-sensitive ac polarography.

Phase-sensitive ac polarography was applied to the simultaneous quantitative determination of 4-nitroanisole, 4-nitrophenol, and 4-nitrocatechol in alkaline solutions. Certain experimental precautions are necessary to determine each compound in the presence of the other two. Thus, 4-nitrocatechol is determined indirectly by forming a yellow ratio chelate with cupric ions, wheras 4-nitroansole is determined directly by the reduction waves of the nitro group. For the determination of 4-nitrophenol, the interferency by the simultaneously present 4-nitrocatechol must be eliminated by masking it by the addition of magnesium ions. The method described permits a qualitative and quantitative analysis of all three compounds in one solution since linear calibration curves are obtained.

Anisoles↗
PubMed1978

P-Nitrophenol-alpha-D-glucopyranoside as substrate for measurement of maltase activity in human semen.

Hitherto, seminal plasma maltase has been measured with maltose as substrate; this method is time consuming and lacks specificity. The use of a synthetic substrate, p-nitrophenol-alpha-D-glucopyranoside, allows accurate and rapid determination of this activity. When maltase is added to the incubation medium (the substrate and reduced glutathione in potassium phosphate buffer, pH 6.8), maintained at 37 degrees C, hydrolysis of the original substrate to p-nitrophenol goes at a constant rate during 4 h. Under optimal conditions of incubation, the Michaelis constant of the reaction, calculated by the Hanes method, was 2.92 +/- 0.84 (SD) X 10(-3) for six different semen samples. Isomaltase appeared to be absent from seminal plasma. The enzyme is stable to freezing and slow thawing and can be stored for at least 26 days at -80 degrees C. Its molecular weight is 259 000. Tris(hydroxymethyl)aminomethane (pH 6.8) exerts a noncompetitive inhibition on the enzyme activity. In 68 men 23 to 45 years old, whose semen analyses were normal, the seminal plasma maltase activity was 467 +/- 135 (SD) mU/g of protein. It was generally decreased in patients with infertility disorders.

Adult↗
PubMed1992

Absence of hepatic p-nitrophenol UDP-glucuronosyltransferase induction by spironolactone in male rats: possible involvement of testosterone.

This study was performed to determine whether the lack of spironolactone induction of hepatic p-nitrophenol UDP-glucuronosyltransferase in male rats could be attributed to a presumed interaction between spironolactone and testosterone. The effect of spironolactone was evaluated in four experimental groups: normal females, normal males, castrated males, and castrated males that received testosterone. Enzyme activity was measured in native microsomes and in microsomes activated with UDP-N-acetylglucosamine or Triton X-100. When the nucleotide was included in the incubations, it was observed that enzyme activity in castrated male rats decreased to values approaching those obtained in normal females. Treatment of castrated animals with testosterone enhanced enzyme activity so that no significant difference existed between this group and normal males. This suggests that testosterone may act as an endogenous inducer of hepatic p-nitrophenol glucuronidation. It was also found that only females and castrated males showed an increase in enzyme activity in response to spironolactone treatment. Thus, the absence of an additive effect of endogenous or exogenous testosterone and spironolactone on UDP-glucuronosyltransferase activity suggests that these compounds could share a common induction mechanism, which appears to reach its maximal capacity in male rats. Possible explanations of this observation are discussed. From the analysis of enzyme activity in native and Triton X-100 activated microsomes, it can be postulated that spironolactone enzyme induction in female and castrated male rats could be attributed to an enhancement in the transferase synthesis rather than to an alteration of the membrane environment.

Animals↗
PubMed1990

Coupled reductive and oxidative degradation of 4-chloro-2-nitrophenol by a co-immobilized mixed culture system.

The restriction of oxygen transfer in Ca-alginate beads used for the immobilization of microbial cells was applied to a coupled reductive and oxidative microbial degradation of the xenobiotic 4-chloro-2-nitrophenol (CNP). The conversion of CNP by Enterobacter cloacae under anaerobic conditions led to the formation of 4-chloro-2-aminophenol (CAP, 81%) and 4-chloro-2-acetaminophenol (CAAP, 16%) after 50 h incubation. CAP, the main reduction product, was further degraded under aerobic conditions by Alcaligenes sp. TK-2, a hybrid strain isolated by conjugative in-vivo gene transfer. Whereas both degradation steps excluded one another in homogeneous systems with free cells, a coupled reductive and oxidative degradation of CNP was observed in one aerated reactor system after co-immobilization of both strains in Ca alginate. The diameter of the alginate beads used for immobilization was recognized as one main factor determining the properties of this mixed culture system.

Aerobiosis↗
PubMed1978

Conversion of p-nitrophenol to 4-nitrocatechol by a Pseudomonas sp.

A strain of Pseudomonas sp. ATCC 29354, isolated from parathionamended flooded soil, converted p-nitrophenol to 4-nitrocatechol which persisted in pure culture. In unsterilized flooded soil, not previously treated with parathion, 4-nitrocatechol was further metabolized by other microorganisms.

Catechols↗
PubMed1975

Uptake, elimination, and biotransformation of the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) by larvae of the aquatic midge Chironomus tentans.

Accumulation of [14C]3-trifluoromethyl-4-nitrophenol ([14C]TFM) by chironomid larvae from sublethal aqueous concentrations is rapid and dependent on hardness of exposure water. TFM is readily biotransformed to at least two more polar derivatives, including sulfated TFM and TFM-glucuronide or galacturonide. Some TFM is also reduced to the phenol amine. Chironomids can quickly eliminate all TFM derivatives as well as the parent [14C]TFM.

Animals↗
PubMed1977

The effect of temperature on the individual stages of the hydrolysis of non-specific-p-nitrophenol esters by alpha-chymotrypsin.

Precise studies were performed on the effect of temperature on the rate and equilibrium parameters characterizing the individual stages of the alpha-chymotrypsin-catalysed hydrolysis of non-specific p-nitrophenol esters at pH 7.40 and 8.50. At both pH values the results indicate that a sharp kinetic anomaly is observed in Arrhenius plots of these parameters for the binding and acylation stages of the process, but not for the deacylation stage. Detailed comparison with other kinetic studies was made, and a comparison with thermal transitions observed in alpha-chymotrypsin by using physical techniques was attempted. A detailed discussion of possible causes of the anomalies is given.

Chymotrypsin↗
PubMed1975

Mercuri-nitrophenol as a reporter group for the conformational change of hemoglobin.

One mole of horse hemoglobin tetramer reacts with 2 moles of 2-chloromercuri-4-nitrophenol (MNP) at beta 93 cysteine. The difference spectra between NMP-bound hemoglobin and hemoglobin, measured with the aid of ascorbic acid and ascorate oxidase [EC 1.10.3.3] as deoxygenation reagents, indicate that the pK of the phenolic hydroxyl group of MNP increases by 0.6 to 0.8 pH unit on deoxygenation of the hemoglobin. The Hill constant of the modified hemoglobin changes with pH. It decreases from about 2.4 at pH 6.8 to about 1.0 at pH 9.0 This effect of the reagent is interpreted as inherent to the reporter groups.

Animals↗