Presence Of Ammonium Ions Research Articles

Analysis of phosphorylated carbohydrates by high-performance liquid chromatography–electrospray ionization tandem mass spectrometry utilising a β-cyclodextrin bonded stationary phase

Chromatographic separation of phosphorylated carbohydrates was achieved on a β-cyclodextrin (CD) bonded HPLC column. Applying acetonitrile–aqueous ammonium acetate gradient elution, the separation of sugar phosphates relied on the combination of anion-exchange and hydrophilic interaction properties of CD bonded phases in the presence of ammonium ions. Furthermore, this solvent system allowed on-line coupling to electrospray ionization mass spectrometry (ESI-MS) and direct structural characterisation of carbohydrate phosphates by tandem mass spectrometry (MS–MS). In addition to the analysis of various pentose and hexose phosphates, the HPLC–ESI-MS–MS method was successfully applied to demonstrate the enzymatic formation of D-1-deoxyxylulose 5-phosphate from pyruvate and glyceraldehyde phosphate catalysed by yeast transketolase.

The electrochemical determination of ammonium based on the selective inhibition of the low-spin iron(II)/(III) system of Prussian blue

A new method is described for the determination of ammonium in aqueous solutions with electrodes modified by Prussian blue (PB). The specific voltammetric response of PB-modified electrodes to ammonium ions is used for their analytical determination. In the presence of ammonium ions, a concentration-dependent inhibition of the low-spin iron(II/III) system of PB occurs. Only thallium and rubidium ions cause similar inhibition. A useful electrochemical determination method is thus available for detecting ammonium ions in the presence of frequently interfering potassium and sodium ions. Paraffin-impregnated graphite electrodes modified with a mechanically transferred PB layer and bulk-modified PB-composite electrodes are studied. The method is applicable within a concentration range which extends from 4 × 10−5 mol/l to 10−2 mol/l NH4 +. The composite electrode is used in an electrochemical flow-through system in conjunction with the Kjeldahl method.

Disruption Analysis of the Gene for a Cold-Regulated RNA-Binding Protein, rbpA1, in Anabaena: Cold-Induced Initiation of the Heterocyst Differentiation Pathway

A cold-regulated operon, rbpA1-rpsU, encodes an RNA-binding protein and a ribosomal protein in Anabaena variabilis M3. The level of expression of this gene cluster was about ten times higher at temperatures below 30 degrees C than at 38 degrees C. To study the role of the RbpA1 protein in vivo, we constructed insertional disruptants of rbpA1. These strains were totally devoid of RbpA1 protein but contained a normal level of the ribosomal protein S21, a product of the rpsU gene. The disruptants were morphologically normal at 38 degrees C, but at 22 degrees C they produced unusual cells at a low frequency. These cells were probably at an initial stage of proheterocyst formation. Various molecular events that are related to heterocyst initiation, namely, excision of the 11-kbp DNA element in nifD and the accumulation of transcripts of xisA and hetR, also occurred in the disruptants at 22 degrees C in the presence of nitrate ions, but these events did not occur in the presence of ammonium ions or at 38 degrees C. The results suggest that RbpA1 is required for enhanced repression of heterocyst initiation at low temperatures in the presence of nitrate. Possible mechanisms of the action of RabA1 are discussed.

Cytotoxin and urease activities of Helicobacter pylori isolates from Japanese patients with atrophic gastritis or duodenal ulcer.

The vacuolating cytotoxin and urease secreted by Helicobacter pylori are thought to be virulent factors. Because vacuolation is potentiated by the presence of ammonium ion, which is produced by urease in vitro, it is of interest to examine whether cytotoxin and urease work reciprocally in the development of atrophic gastritis or duodenal ulcer. In the present study, patients (all H. pylori-positive) were divided into four groups: mild atrophic gastritis (group 1; nine patients), severe atrophic gastritis (group 2; 36 patients), duodenal ulcer with mild atrophic gastritis (group 3; 19 patients) and duodenal ulcer with severe atrophic gastritis (group 4; 12 patients). Cytotoxin production and urease activity of H. pylori isolated from these patients were analysed. Cytotoxin production was observed in four of nine (44.4%), 28 of 36 (77.8%), 11 of 19 (57.9%) and eight of 12 (66.7%) isolates from groups 1, 2, 3 and 4, respectively. Cytotoxin-producing H. pylori isolates were found significantly more in patients with severe atrophy than in patients with mild atrophy (P = 0.048). The mean of relative activity of cytotoxin in H. pylori isolate was 1.6 +/- 2.3, 7.9 +/- 7.4, 5.8 +/- 6.0 and 9.0 +/- 9.1 in groups 1, 2, 3 and 4, respectively. Helicobacter pylori isolates from severe atrophy or duodenal ulcer patients in groups 2 or 4 possessed significantly higher activity than those from non-ulcer patients in group 1 (P = 0.017 and 0.030, respectively). The mean of urease activity was 8.6 +/- 4.6, 10.0 +/- 5.9, 10.0 +/- 8.5 and 11.2 +/- 7.7 IU/mg in groups 1, 2, 3 and 4, respectively. These differences indicated no statistical significance. In each H. pylori isolate, the production of cytotoxin and urease were independent, which indicated that there was no reciprocal effect between them in vivo. Thus, cytotoxin-producing H. pylori isolates were more prevalent in patients with severe atrophic gastritis and the cytotoxin activities of H. pylori isolates from the patients with severe atrophic gastritis or duodenal ulcer were much higher than those from the patients with mild atrophic gastritis, which suggested that vacuolating cytotoxin may be a disease-inducing factor.

Caesium ion-selective electrodes based on crowned benzoquinones

Three new derivatives of benzo-15-crown-5 were examined as potential caesium ion-selective ionophores in PVC membrane electrodes. The ionophores were 2,3-benzoquino[15]crown-5,2-bromo-1,4-dihydroxybenzo[15]crown-5 and 5-bromo-2,3-benzoquino[15]crown-5. PVC membranes plasticized with 2-nitrophenyl octyl ether, and incorporating the secondary ion exchanger potassium tetrakis(4-chlorophenyl)borate were used throughout this study. Interferent studies for each electrode were carried out to assess electrode selectivity in the presence of ammonium ion, alkali and alkaline earth ions and selected transition metals. A graphical method of representing selectivity coefficients is provided together with the separate solution technique for selectivity determination. Dynamic response, precision, lifetime and temperature studies was also reported. The benzoquinone crown ethers proved to be good caesium ionophores, displaying near-Nernstian responses to this ion, in the range 10–1–10–4.5 mol l–1. The electrode incorporating the 2,3-benzoquino[15]crown-5 ionophore had the highest selectivity for caesium ions over alkali and alkaline earths studied.

URE3] as an altered URE2 protein: evidence for a prion analog in Saccharomyces cerevisiae.

A cytoplasmically inherited element, [URE3], allows yeast to use ureidosuccinate in the presence of ammonium ion. Chromosomal mutations in the URE2 gene produce the same phenotype. [URE3] depends for its propagation on the URE2 product (Ure2p), a negative regulator of enzymes of nitrogen metabolism. Saccharomyces cerevisiae strains cured of [URE3] with guanidium chloride were shown to return to the [URE3]-carrying state without its introduction from other cells. Overproduction of Ure2p increased the frequency with which a strain became [URE3] by 100-fold. In analogy to mammalian prions, [URE3] may be an altered form of Ure2p that is inactive for its normal function but can convert normal Ure2p to the altered form. The genetic evidence presented here suggests that protein-based inheritance, involving a protein unrelated to the mammalian prion protein, can occur in a microorganism.

K(+)-, hypoosmolarity-, and NH4(+)-induced taurine release from cultured rabbit Müller cells: role of Na+ and Cl- ions and relation to cell volume changes.

The release of preloaded radiolabeled taurine (TAU) from cultured rabbit Müller cells [14-21 days in vitro (DIV)] was measured before and after treatment with the following stimuli: 1) isoosmotic 65 mM KCl; 2) a medium made hypoosmotic by uncompensated lowering of Na+ by 40-100 mM; and 3) NH4Cl ranging from 0.25 to 5 mM. The same stimuli were tested for their effect on the cell volume by the 3-O-methyl-D-glucose (OMG) uptake method of Kletzien et al. (Anal Biochem 68:537, 1975). Hypoosmotic media and 65 mM KCl stimulated TAU release, and the release was well correlated with the increase of cell volume. The stimulatory effect of 65 mM KCl was abolished by isotonic removal of Cl- or Na+, and omission of either ion markedly enhanced the basal release of TAU. The results are roughly consistent with the characteristics of the swelling-induced TAU release reported for cultured astrocytes and neurons of various CNS regions, and also for freshly isolated, nondissociated retina. Taken together, the results are indicative of a significant role of TAU release from Müller cells, in the osmosensory response of the retina. Ammonium chloride stimulated TAU release in a dose-dependent manner, a significant stimulation being already observed at 0.5 mM, a concentration that is frequently measured in brain during acute hyperammonemia. The effect of NH4Cl was strictly chloride dependent at 0.5-2 mM, but partly Cl- independent at 5 mM. The Kletzien's method did not appear to be well suited for measuring cell volume in the presence of ammonium ions.(ABSTRACT TRUNCATED AT 250 WORDS)

Foot-and-mouth disease virus particles contain replicase protein 3D.

An antibody against the Escherichia coli-expressed RNA polymerase of foot-and-mouth disease virus (FMDV) reacts with the virus in ELISA and radioimmunoprecipitation experiments and with a protein of the disrupted virus particle in an immunoblot analysis. Treatment of the virus with trypsin, which cleaves capsid protein VP1 and a 56-kDa polypeptide present in trace amount in the particles, reduces the level of the reaction in ELISA and radioimmunoprecipitation and eliminates the immunoblot reaction. Electron microscopy showed that only approximately 20% of the virus particles reacted with the anti-polymerase antibody, whereas most reacted with an antibody against the immunodominant G-H loop of the virus. In the presence of ammonium ions, the expressed polymerase degrades the RNA of the virus into molecules sedimenting at approximately 12 S, indicating that it can act as a hydrolytic as well as a polymerizing enzyme. Moreover, the RNA in trypsin-treated virus particles is degraded when incubated at 37 degrees C, suggesting that the cleaved 56-kDa protein still possesses hydrolytic activity. In addition, the anti-polymerase antibody, which inhibits the polymerase activity of the E. coli-expressed protein, also partially inhibits the hydrolytic activity of the previously described endonuclease of the virus particle, suggesting that this enzyme is identical with the polymerase or forms part of it.

無電解Ｎｉ‐Ｐ皮膜物性に与える錯化剤の影響

Effects of complexing agents and ammonium ion on physical properties of electroless Ni-P films were systematically studied as a function of bath pH using citrate and glycine baths, with and without ammonium sulfate. The deposition rate and the phosphorus content of Ni-P films were strongly influenced by the species of complexing agent and the presence of ammonium ion in the bath. The physical properties of Ni-P films, such as deposition rate, saturation magnetization and specific resistance were discussed as a function of phosphorus content. Internal stress of Ni-P films, however, could not be determined as a function of phosphorus content.

Formation of chloroamines from styrene under conditions mimicking those of water "chlorination" treatment.

The reaction of styrene with sodium hypochlorite in the presence of ammonium ion in 0.3 M phosphate buffer (pH 6.0) at room temperature afforded N-chloro-1-phenyl-2-chloroethylamine and N,N-dichloro-1-phenyl-2-chloroethylamine. 1-Phenyl-2-chloroethylamine hydrochloride, obtained as the reduction product of the two N-chloroamines, was shown to be mutagenic in the Salmonella typhimurium test.

Role of glutamate dehydrogenase reaction in the control of citrate pool in yeast

1.1. Role of NADP-glutamate dehydrogenase in the depletion of citrate was analyzed using permeabilized yeast cells.2.2. Citrate was converted to 2-oxoglutarate, which was then metabolized to glutamate by NADP-glutamate dehydrogenase in the presence of ammonium ion.3.3. Formation of 2-oxoglutarate plus glutamate was in good agreement with the concentration of citrate decreased. Glutamate formation can be a good indicator of the depletion of citrate, because 70% of the citrate decreased was converted to glutamate.4.4. Glycolytic activity was closely correlated with the decrease in citrate under the in situ conditions.5.5. NADP-glutamate dehydrogenase increased in anaerobically grown yeast cells.6.6. An effective depletion of citrate by increased synthesis of NADP-glutamate dehydrogenase can explain the lowered mechanism of citrate causing glycolytic stimulation under the anaerobic growth conditions of yeast.

The multimerization state of retroviral RNA is modulated by ammonium ions and affects HIV-1 full-length cDNA synthesis in vitro.

Genomic human immunodeficiency virus type 1 (HIV-1) RNA fragments containing the dimer linkage structure (DLS) can be dimerized and multimerized in the presence of NH4+ and in the absence of any other cation and any viral or cellular protein. This effect strongly supports the notion that dimerization and multimerization of genomic RNA occurs via purine-quartet formation in quadruple helical RNA structures. The efficiency of RNA dimerization and multimerization in the presence of ammonium ions is about 400 fold increased as compared to alkali metal ions such as potassium. Dimerized retroviral RNA representing a pseudodiploid genome could account for genetic recombination within the virion and during reverse transcription. Application of a novel South-Northern-Blotting procedure with biotinylated RNA and digoxigenin-labelled cDNA in vitro reveals that efficient human- and bovine tRNA(Lys3) primed full-length cDNA-synthesis only takes place with a predominantly monomerized RNA template. Dimerization and multimerization of the RNA significantly reduces full-length cDNA-synthesis. This suggests that monomerization of the dimerized RNA, effected by deionization in vitro, is essential for efficient retroviral reverse transcription in vivo.

Thylakoid membrane energization and swelling in photoinhibited Chlamydomonas cells is prevented in mutants unable to perform cyclic electron flow

Photoinhibition of Photosystem II in unicellular algae in vivo is accompanied by thylakoid membrane energization and generation of a relatively high ΔpH as demonstrated by (14)C-methylamine uptake in intact cells. Presence of ammonium ions in the medium causes extensive swelling of the thylakoid membranes in photoinhibited Chlamydomonas reinhardtii but not in Scenedesmus obliquus wild type and LF-1 mutant cells. The rise in ΔpH and the related thylakoid swelling do not occur at light intensities which do not induce photoinhibition. The rise in ΔpH and membrane energization are not induced by photoinhibitory light in C. reinhardtii mutant cells possessing an active Photosystem II but lacking cytochrome b6/f, plastocyanin or Photosystem I activity and thus being unable to perform cyclic electron flow around Photosystem I. In these mutants the light-induced turnover of the D1 protein of Reaction Center II is considerably reduced. The high light-dependent rise in ΔpH is induced in the LF-1 mutant of Scenedesmus which can not oxidize water but otherwise possesses an active Reaction Center II indicating that PS II-linear electron flow activity and reduction of plastoquinone are not required for this process. Based on these results we conclude that photoinhibition of Photosystem II activates cyclic electron flow around Photosystem I which is responsible for the high membrane energization and ΔpH rise in cells exposed to excessive light intensities.

Tannins and Related Compounds. CXVIII. Structures, Preparation, High-Performance Liquid Chromatography and Some Reactions of Dehydroellagitannin-Acetone Condensates.

The dehydroellagitannins having a dehydrohexahydroxydiphenoyl ester group in the molecule were found to undergo highly regio- and stereospecific condensation with acetone in the presence of ammonium ion under almost neutral conditions. This reaction was successfully applied to high-performance liquid chromatographic analysis to detect the dehydroellagitannins in the plant extract. Furthermore, the reactions of the acetone condensates with L-cysteine methyl ester were examined, and appear to be applicable to structural studies of dehydroellagitannins.

Some comparisons of cellulases from two different strains of aspergillus fumigatus

Michaelis-Menten kinetics for exoglucanase, endoglucanase and β-glucosidase activities from two different strains of Aspergillus fumigatus were compared in the absence and the presence of ammonium ions. Inhibitory effects, evident in only one strain, were quantified, suggesting non-competitive inhibition for endoglucanase and β-glucosidase, but competitive inhibition of exocellulase. Possible reasons are discussed.

Kinetics of growth of calcite crystals in presence of ammonium ions

AbstractThe growth of calcite crystals from an aqueous supersaturated solution of initial concentration 0.15 mol m−3 containing 10 mol m−3 of (NH4)2CO3 has been studied at 298 K. The progress of growth has been followed through determining the composition of the solution by chemical analysis. The crystal growth is controlled by the surface reaction mechanism and satisfies a kinetic equation of the second order with the rate constant 3.7 × 10−6 m4 mol−1 s−1 that is independent on the surface area of the present solid. NH4+ ions do not change the crystal growth mechanism but decrease the growth rate of calcite crystals.

The liver parenchymal cells of rainbow trout (Salmo gairdneri) endocytose mannose-terminated glycoproteins

A mannose-terminated glycoprotein,(125)I-invertase, was taken up and degraded by isolated rainbow trout liver cells at 12°C. The uptake was inhibited by EGTA and no degradation occurred in the presence of ammonium ions. The liver cell suspension was fractionated by differential centrifugation in parenchymal and nonparenchymal cells, respectively. The parenchymal liver cells seemed to be the most active cells in uptake of labelled invertase bothin vitro andin vivo. Only negligible amounts of ligand were recovered in the nonparenchymal cells. Internalization of(125)I-invertase at different temperatures was demonstrated indirectly by releasing surface-bound ligand with EGTA. Ligand was internalized even at 0°C in trout liver cells.In vitro uptake of(125)I-invertase was inhibited by excess unlabelled invertase, by mannan and by N-acetylglucosamine.These data suggest that invertase is endocytosed by a mannose-specific pathway by the parenchymal liver cells of rainbow trout.

Urease activity on the phylloplane ‐ measurement and activity levels following urea application

Abstract Previously employed urea hydrolysis method (4) for the determination urease activity on phylloplanes fails if pre‐applied urea is present as a residue from fertilizer, urine or other sources prior to assay. Under such conditions the total urease activity is underestimated and the extracellular component is overestimated. A modified method is proposed that employs an additional measurement where mercuric chloride is a component of the assay incubating medium, which enables a correction to be made to urease activities estimated under such conditions. However, where no urea is present prior to the assay, previously employed methods are acceptable. Using the proposed modifications, urease activities on the phylloplane which had received urea dressings previously were shown to be depressed over the following 2 or 3 days due to the presence of ammonium ions.

Candidacidal Activity of the Neutrophil Myeloperoxidase System Can Be Protected From Excess Hydrogen Peroxide by the Presence of Ammonium Ion

AbstractExcessive concentrations of hydrogen peroxide inhibit the neutrophil myeloperoxidase system, presumably by inactivating the hypochlorous acid produced by this system. Ammonium ion generated by neutrophils and other cells can react with hypochlorous acid to produce monochlo-ramine, an oxidant with good microbicidal activity, but relative resistance to inactivation by other compounds. In an assay based on the oxidation of 5-thio-2-nitrobenzoic acid, hydrogen peroxide reacted more readily with sodium hypochlorite (used as a source of hypochlorous acid) than with monochloramine. Also, in this assay Candida albicans yeast inactivated the oxidant activity of hypochlorous acid more completely than they did that of monochloramine. The killing of Candida by sodium hypochlorite, as determined in a standard colony count microbicidal assay, was inhibited by equimolar and greater concentrations of hydrogen peroxide; killing of this organism by monochlo- ramine was not affected by a tenfold excess concentration of hydrogen peroxide. In microbicidal assays using 4 mU of myeloperoxidase and optimal or excessive concentrations of hydrogen peroxide or glucose and glucose oxidase to generate hydrogen peroxide, the excessive concentrations inhibited killing of Candida, but not Staphylococcus aureus. The inhibition of Candida killing could be reversed by addition of ammonium ion to convert hypochlorous acid to monochloramine. These results indicate that for certain organisms such as C albicans, conversion of hypochlorous acid to monochloramine by reactions with ammonium ion may extend the range of hydrogen peroxide concentrations under which killing by the myeloperoxidase system can occur by protecting the necessary microbicidal oxidants from inactivation by excess hydrogen peroxide.

Candidacidal activity of the neutrophil myeloperoxidase system can be protected from excess hydrogen peroxide by the presence of ammonium ion

Excessive concentrations of hydrogen peroxide inhibit the neutrophil myeloperoxidase system, presumably by inactivating the hypochlorous acid produced by this system. Ammonium ion generated by neutrophils and other cells can react with hypochlorous acid to produce monochloramine, an oxidant with good microbicidal activity, but relative resistance to inactivation by other compounds. In an assay based on the oxidation of 5-thio-2-nitrobenzoic acid, hydrogen peroxide reacted more readily with sodium hypochlorite (used as a source of hypochlorous acid) than with monochloramine. Also, in this assay Candida albicans yeast inactivated the oxidant activity of hypochlorous acid more completely than they did that of monochloramine. The killing of Candida by sodium hypochlorite, as determined in a standard colony count microbicidal assay, was inhibited by equimolar and greater concentrations of hydrogen peroxide; killing of this organism by monochloramine was not affected by a tenfold excess concentration of hydrogen peroxide. In microbicidal assays using 4 mU of myeloperoxidase and optimal or excessive concentrations of hydrogen peroxide or glucose and glucose oxidase to generate hydrogen peroxide, the excessive concentrations inhibited killing of Candida, but not Staphylococcus aureus. The inhibition of Candida killing could be reversed by addition of ammonium ion to convert hypochlorous acid to monochloramine. These results indicate that for certain organisms such as C albicans, conversion of hypochlorous acid to monochloramine by reactions with ammonium ion may extend the range of hydrogen peroxide concentrations under which killing by the myeloperoxidase system can occur by protecting the necessary microbicidal oxidants from inactivation by excess hydrogen peroxide.