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PubMed1997

Light emission resulting from hydroxylamine-induced singlet oxygen formation of oxidizing LDL particles.

Oxidation of low-density lipoprotein (LDL) by low amounts of cupric ions resulted in the formation of singlet oxygen (1O2, 1 delta g) when hydroxylamine (NH2OH) was added. Direct evidence on this excited species came from partial spectral resolution of the emitted light in the red spectral region (634 nm and 703 nm), which can be attributed to the dimol decay of singlet oxygen. Additional evidence for the existence of singlet oxygen came from the enhancing effect of deuterium oxide buffer (D2O) on chemiluminescence intensity and the quenching effect of sodium azide. A linear correlation between NH2OH-dependent chemiluminescence intensity and the amount of diene conjugates (DC) formed in this reaction was observed. Removal of adventitious transition metals by adequate chelators prevented chemiluminescence in this system; NH2OH was also found to efficiently decrease metabolites of lipid peroxidation (LPO). Our findings are consistent with a sequence of reactions in which NH2OH first converts transition metals to their reduced state, thereby stimulating the formation of alkoxy- and peroxyradicals. Peroxyradicals decompose in a bimolecular Russel reaction to hydroxyl compounds and singlet oxygen while the majority of alkoxy radicals are eliminated by a secondary reaction with NH2OH. Identical effects were observed when reducing antioxidants such as ascorbic acid or trolox C were used instead of hydroxylamine.

Antioxidants↗
PubMed1969

Anaphylatoxin release from the third component of human complement by hydroxylamine.

Treatment of highly purified preparations of the third component of complement (C3) with 0.5M hydroxylamine at 20 degrees C for 15 to 30 minutes, followed by acidification, resulted in dissociation of a peptide from the C3 molecule. The isolated fragment (molecular weight, 7600) resembled enzymatically liberated anaphylatoxin (C3a) with respect to size, charge, amino acid composition, and biological activity. Its capacity to contract smooth muscle was inhibitable by antihistamines; it also produced tachyphylaxis and desensitization of the guinea pig ileum to C3a. Thus native C3 probably contains an esterlike bond and hydroxylamine-liberated anaphylatoxin may represent one of the polypeptide chains of the C3 molecule.

Amino Acids↗
PubMed2002

Solvents inducing oxidation of hydroxylamines.

Hydroxylamines gradually undergo oxidation to their oximes on being dissolved in organic solvent (e.g. methanol). This phenomenon was followed by (1)H-NMR and liquid chromatography-mass spectrometry (LC-MS). The oxidation rate was estimated from the peak area observed on the mass chromatogram at the protonated molecule or fragment ion on LC-atmospheric pressure chemical ionization (APCI)-MS. The results showed that the oxidation rate of hydroxylamines depended on the solvent type.

Calibration↗
PubMed1988

Dipeptidylpeptidase IV--inactivation with N-peptidyl-O-aroyl hydroxylamines.

Eleven N-peptidyl-O-aroyl hydroxylamines have been synthesized and their hydrolytic stability, acidity and properties during reaction with dipeptidyl peptidase IV (E.C. 3.4.14.5) investigated. N-peptidyl-O-(4-nitrobenzoyl) hydroxylamines act as irreversible inhibitors of serine proteases. The serine enzyme, dipeptidyl peptidase IV (DP IV), is inactivated by substrate analog derivatives of this class by a suicide inactivation mechanism. During the enzyme reaction of DP IV with the suicide substrates most molecules are hydrolyzed but some irreversibly inactivate the target enzyme. In contrast to porcine pancreatic elastase and thermitase, DP IV exhibits a high ratio for hydrolysis of the compounds versus inhibition during their interaction with the enzyme. Variation of the leaving aroyl residue lowers this ratio. Variation of the substrate analog peptide moieties of the DP IV-inhibitors increases their ability to inhibit the enzyme to a remarkable extent. Possible reaction pathways are discussed.

Dipeptides↗
PubMed1975

Effect of hydroxylamine on the consequences of long-lasting administration of morphine in mice. III. Effect on preferred drinking of morphine solution.

C57BL/6J mice were periodically required to drink a morphine solution for one, ten or sixteen weeks and then injected intracranially with the mutagens hydroxylamine or sodium nitrite. Whereas before the injection of the drugs the mice demonstrated a definite preference for morphine, after hydroxylamine this preference disappeared. Sodium nitrite had no such effect on the consumption of morphine solution.

Animals↗
PubMed1975

Effects of hydroxylamine on the consequences of long-lasting administration of morphine in mice. I. Effect on the morphine tolerance.

C57BL/6J mice were injected daily with increasing doses of morphine sulfate for 5 weeks. Twenty-four hours after the final morphine administration, they were injected intracranially with 10, 20 or 50 mul of a 0.3 M solution of hydroxylamine. Two weeks later, hot plate testing indicated that hydroxylamine interfered with the developed tolerance of the mice to morphine.

Animals↗
PubMed2004

Nitrite oxidation inhibition by hydroxylamine: experimental and model evaluation.

A proposed approach for biological nitrogen removal significantly reduces cost by reducing biomass production and carbon requirements via inhibition of nitrite oxidation (NO2- to NO3-). Batch experiments were conducted to examine the effect of hydroxylamine (HM) on nitrite oxidizers, ammonia oxidizers, and nitrite reducers. Hydroxylamine effect experiments were done at initial pH values of 7.4-8.4, nitrogen concentrations of 100 mg N/L, biomass concentrations of 100-400 mg VSS/L and HM dosages up to 43 mg/L. Nitrite oxidizer activity was completely inhibited by HM at dosages of 7.0 and 8.9 mg/L for pH values of 8.4 and 7.6, respectively. Relatively low HM concentrations (0.35-5.5 mg/L) can be used to completely inhibit nitrite oxidation, but do not significantly affect ammonia oxidizers and nitrite reducers. A model developed to describe the effect of pH on nitrite oxidation rate fits the data well (R2 = 0.89) with values for Vmax of 0.372 (mg N/mg VSS-hr), pH* of 7.72, and the inhibition constant Kh of 0.154. Incorporation of HM inhibition into the model provided a good fit to relative nitrite oxidation rate as a function of undissociated HM concentration (R2 = 0.80, Vmax = 0.028 mg N/mg VSS-hr, pH = 7.89, Kh = 0.302, a = 0.195, and Ki= 0.277 mg/L).

Biomass↗
PubMed2004

Dipyridamole inhibits hydroxylamine augmented nitric oxide (NO) production by activated polymorphonuclear neutrophils through an adenosine-independent mechanism.

Polymorphonuclear neutrophils (PMN) are thought to play a role in reperfusion injury and ischemia. These effects are partly mediated by toxic oxygen species (superoxide anion, hydrogen peroxide and hydroxyl radical) acting at the level of the endothelium. It was demonstrated recently that the superoxide anion reacts with nitric oxide (NO) and that interaction leads to the generation of highly toxic peroxynitrite. Several drugs were tested so far in order to affect PMN function. It was demonstrated that dipyridamole (2,6-bis-diethanolamino-4,8-dipiperidinopyrimido-(5,4-d)-pyrimidine) can influence neutrophil function by inhibiting adenosine uptake. However, this action can not fully explain all of the observed effects of dipyridamole action on PMN metabolism. The aim of our study was to evaluate the influence of dipyridamole on nitric oxide production by activated polymorphonuclear neutrophils. Incubation of PMNs with hydroxylamine (HA) and phorbol myristate acetate (PMA) generated nitrite (36.4+/-4.2 nmol/h 2x10(6) PMN), dipyridamole at 100 micromol/l, 50 micromol/l and 10 micromol/l caused a considerable drop in nitrite production (11.8+/-1.8, 19.7+/-2.7 and 27.4+/-3.2 nmol/h, respectively). Neither adenosine nor the adenosine analogue could mimic the dipyridamole effect. Moreover theophylline, an adenosine inhibitor could not reverse the dipirydamole action on PMN metabolism. We also found that dipyridamole inhibited hydrogen peroxide release from neutrophils. Catalase that scavenges hydrogen peroxide also largely abolished nitric oxide release from PMN. It is evident that dipyridamole inhibits hydroxylamine-augmented nitric oxide production by activated polymorphonuclear neutrophils through an adenosine-independent mechanism.

Adenosine↗
PubMed1989

Antihypoxic effect of the hydroxylamine derivative HB-7.

The antihypoxic effect of the newly-synthesized hydroxylamine barbiturate HB-7, compared with the effects of phenobarbital and pentobarbital, was studied in experiments on albino mice, using the following models of hypoxia: hypobaric, anoxic, asphyctic and haemic. A dose-effect dependence was established when the survival of the mice was prolonged under the effects of the barbiturates tested, applying the asphyctic and haemic hypoxy tests. The latter two tests were also used to determine the average effective doses (ED60) of the barbiturates. HB-7 was superior in its action to phenobarbital and pentobarbital, manifesting higher protective indices (PI-LD50: ED50): for HB-7 PI is 4.2, for phenobarbital--3.2 and for pentobarbital--2.5, using the haemic hypoxy test. It is concluded that HB-7, i.e. 2-hydroxylamine-5-ethyl-5-sec, pentylbarbituric acid, manifests a marked protective effect in the hypoxy tests used, exceeding in some cases the effects of phenobarbital and pentobarbital.

Animals↗
PubMed1984

Oxidation of ammonia and hydroxylamine to nitrate in the rat.

We have demonstrated that ammonia is oxidized to nitrate in the rat. Male Sprague-Dawley rats gavaged with 1 000 mumol 15N-ammonium chloride each day for five days were found to excrete low, but significant, amounts of excess 15N-nitrate in their urines on the five days of treatment and on the five subsequent days. We recovered a total of 0.28 +/- 0.03 mumol excess 15N-nitrate (mean +/- SE) per rat, which indicates that ammonia is converted to nitrate with a yield of about 0.0080%. 15N-Hydroxylamine was oxidized in the rat to 15N-nitrate with a yield of 4.7%, but oxidation of 15N-labeled glycine and L-glutamic acid to 15N-nitrate could not be detected. These results suggest that hydroxylamine, but not glycine or L-glutamic acid, may be an intermediate in the ammonia oxidation process. The injection of rats with Arochlor 1254 failed to stimulate nitrate synthesis, which indicates that the cytochrome P-450 drug metabolizing system is probably not involved in ammonia oxidation. Carbon tetrachloride, which causes hepatic lipid peroxidation, produced a small, but significant, increase in nitrate synthesis. Our results are consistent with the hypothesis that ammonia is oxidized in vivo by a non-enzymatic process involving reactive oxygen species. We estimate that a 215 g rat produces 3.0 mumol of nitrate per day by this process. The significance of our results to the problem of endogenous N-nitroso compound formation in man is discussed.

Ammonium Chloride↗
PubMed1978

Biological functions of hydroxylamine inactivated influenza virus.

Hydroxylamine inactivates members of the orthomyxovirus group. Studies with inactivated influenza virus indicate that the genome of such virus does not serve for the production of functional viral proteins. Additional evidence indicated that the genome may, however, undergo limited replication. These observations are correlated with the inactivation of influenza virus and the known mechanism of action of hydroxylamine.

Genes, Viral↗
PubMed1995

Nature of the inactivation of elastase by N-peptidyl-O-aroyl hydroxylamine as a function of pH.

The mechanism of inactivation of porcine pancreatic elastase (PPE) by N-peptidyl-O-aroylhydroxylamine was studied by X-ray crystallography. The inactivator forms a stable complex with the enzyme by means of a covalent attachment to the active site Ser 203(195) O gamma. The nature of the complex is, however, different depending on the pH at which the inactivation reaction occurs. At pH 5, the complex formed is a hydroxylamine derivative of Ser 203(195) in which the O gamma of serine is the oxygen of the hydroxylamine derivative. At pH 7.5, the complex formed is a carbamate derivative at Ser 203(195) O gamma. In both types of complexes, the inactivator binds in the S' subsites of the enzyme instead of forming the usual antiparallel beta-sheet with the S subsites. The implication for the mechanism of inactivation at different pHs is discussed.

Animals↗
PubMed1997

Ab Initio Potential Energy Surface and Internal Torsional-Wagging States of Hydroxylamine

The two-dimensional potential energy surface describing the interaction of the large-amplitude torsional and wagging motions in hydroxylamine has been determined from ab initio calculations. This surface has been sampled by a large set of grid points from a two-dimensional configuration space spanned by the torsional and wagging coordinates. At each grid point, the geometry optimization has been performed using the second-order Moller-Plesset perturbation theory with the basis set 6-311 + G(2d, p). At the optimized geometry, the single-point calculation of the electronic energy has been carried out using a larger basis set 6-311 + G(3df, 2p). This method was verified to yield the results comparable to those obtained by a direct optimization of the geometry with the basis set 6-311 + G(3df, 2p) which had been used by A. Chung-Phillips and K. A. Jebber (1995. J. Chem. Phys. 102, 7080-7087) to calculate the energies of only three points in the potential energy surface of hydroxylamine. The trans and cis local minima have been found on the determined potential energy surface. The localization features of the torsional-wagging states have been studied by solving the two-dimensional Schrodinger equation for the coupled torsional and wagging motions. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Quantification of superoxide radicals and peroxynitrite in vascular cells using oxidation of sterically hindered hydroxylamines and electron spin resonance.

The reactions of two hydroxylamines, 1-hydroxy-3-carboxy-pyrrolidine (CP-H) and 1-hydroxy-2,2,6,6-tetramethyl-4-oxo-piperidine (TEMPONE-H), with superoxide radicals and peroxynitrite were studied. In these reactions corresponding stable nitroxyl radicals 3-carboxy-proxyl (CP) and 1-hydroxy-2,2,6,6-tetramethyl-4-oxopiperidinoxyl (TEMPONE) are formed and the amount of them can be quantified by electron spin resonance (ESR). It was found that CP-H and TEMPONE-H provide almost the same efficacy in assaying peroxynitrite by ESR in vitro at pH 7.4. The formation of superoxide radicals in suspensions of cells was discriminated from that of peroxynitrite using superoxide dismutase or dimethyl sulfoxide as competitive reagents. The stability of the radicals CP and TEMPONE in the presence of ascorbate or thiols was studied in vitro. The reduction rate of CP by ascorbate was 66-fold slower than the rate of reduction of TEMPONE. Therefore, the quantification of the formation of superoxide radicals and of peroxynitrite is much less affected by ascorbic acid when CP-H, but not TEMPONE-H, is used. Both TEMPONE-H and CP-H were used to determine the formation rates of superoxide radicals and peroxynitrite in suspensions of cultured aortic smooth muscle cells and endothelial cells, in washed ex vivo platelets, and in blood treated with glycerol trinitrate (GTN) as an NO donor. It was shown that both the acute addition of GTN (0.5 mM) to vascular cells and the incubation of smooth muscle or endothelial cells in culture with 0.1 mM GTN for 24 h enhance significantly the formation of reactive oxygen species in cells. The rates of of superoxide radical formation were increased at least in two times and peroxynitrite was detected. Hydroxylamines TEMPONE-H and CP-H can be used as nontoxic compounds in ESR assay capable of quantifying the formation of superoxide radicals and peroxynitrite in suspensions of cells and in the whole blood with high sensitivity.

Analysis of Variance↗
PubMed1994

Dapsone-induced hematologic toxicity: comparison of the methemoglobin-forming ability of hydroxylamine metabolites of dapsone in rat and human blood.

The relative methemoglobin (MetHgb) forming ability of two metabolites of dapsone, dapsone hydroxylamine (DDS-NOH) and monoacetyldapsone hydroxylamine (MADDS-NOH), were compared in rat and human whole blood. Concentration-response curves for the two metabolites were generated in vitro in whole blood. Data were fit to both the Emax and Sigmoid Emax models. The Emax values for MetHgb formation in rat blood for MADDS-NOH and DDS-NOH fitted to the Emax model were 83 (8) and 84 (2)%, while the EC50 values were 1087 (283) and 828 (104) microM, respectively (mean +/- SD). Neither these values nor those generated for the Sigmoid Emax model differed significantly between the two metabolites. Similarly, the Emax values in human blood for MADDS-NOH and DDS-NOH fitted to the Emax model were 79 (5) and 80 (2)%, while the EC50 values were 90 (17) and 95 (19) microM, respectively. These values also did not differ between the two metabolites using either pharmacodynamic model. MetHgb was produced at the same rate, reached similar peak concentrations, and exhibited the same rate of decline with both metabolites. The area under the MetHgb content versus time curve did not differ between the two metabolites. These data demonstrate that MADDS-NOH and DDS-NOH are equipotent and equally efficacious in their MetHgb-forming ability. Investigation of the disposition of these metabolites is necessary to assess their relative role in dapsone-induced toxicity in vivo.

Adult↗
PubMed2002

The roles of the three gene copies encoding hydroxylamine oxidoreductase in Nitrosomonas europaea.

The nitrifying bacterium Nitrosomonas europaea contains three copies of the gene (hao) encoding hydroxylamine oxidoreductase (HAO), the second enzyme in the nitrification pathway which oxidizes NH(2)OH to NO(2)(-). The nucleotide sequences of the hao genes differ by only one nucleotide. Two of the three gene copies have identical promoter sequences, while the third promoter has a different nucleotide sequence. Mutant strains with two of the three copies of hao inactivated were created by insertional inactivation, using DNA cassettes containing kanamycin- and gentamycin-resistance genes. All three double-mutant combinations were obtained. These double mutants were phenotypically identical under the conditions tested. Two of these double mutants were similar to wild-type cells or cells having a single hao copy inactivated regarding growth rates or hydroxylamine-dependent O(2) uptake activity, but had only about 50% of the wild-type level of in vitro HAO activity and hao mRNA. The third hao double mutant had an unstable genotype, resulting in recombination of the gentamycin marker into another copy of hao. The N. europaea genomic sequence was recently completed, revealing the locations of the copies of hao and other nitrification genes. Comparison with the arrangement of hao genes in the closely related strain, Nitrosomonas sp. strain ENI-11, showed a similar organization.

Genes, Bacterial↗
PubMed1993

Purification of hydroxylamine oxidase from Thiosphaera pantotropha. Identification of electron acceptors that couple heterotrophic nitrification to aerobic denitrification.

Thiosphaera pantotropha, a Gram-negative heterotrophic nitrifying bacterium, expresses a soluble 20 kDa monomeric periplasmic hydroxylamine oxidase that differs markedly from the hydroxylamine oxidase found in autotrophic bacteria. This enzyme can use the periplasmic redox proteins, cytochrome c551 and pseudoazurin as electron acceptors, both of which can also donate electrons to denitrification enzymes. A model of electron transfer is proposed, that suggests a coupling of nitrification and provides a mechanism by which nitrification can play a role in dissipating reductant.

Electron Transport↗
PubMed1983

Stable nitrones from 17 beta-Hydroxylamine derivatives of 8 beta- and 8 alpha-estrone.

17 beta-Hydroxylamine derivatives of 8 beta and 8 alpha-estrone can be obtained by reduction of the corresponding oximes with diborane or NaCNBH3. The products can be converted easily and reversibly to nitrones by addition of aldehydes or ketones. The nitrones are more stable than the corresponding hydroxylamines, and may be used as protecting groups.

Chemical Phenomena↗