Ammonia In Medium Research Articles

Molybdenum cofactor amounts in Chlamydomonas reinhardtii depend on the Nit5 gene function related to molybdate transport

ABSTRACTStrain 21gr from Chlamydomonas reinhardtii is a cryptic mutant defective in the Nit5 gene related to the biosynthesis of molybdenum cofactor (MoCo). In spite of this mutation, this strain has active MoCo and can grow on nitrate media. In genetic crosses, the Nit5 mutation cosegregated with a phenotype of resistance to high concentrations of molybdate and tungstate. Molybdate/tungstate toxicity was much higher in nitrate than in ammonium media. Strain 21gr showed lower amounts of MoCo activity than the wild type both when grown in nitrate and after growth in ammonium and nitrate induction. However, nitrate reductase (NR) specific activity was similar in wild type and 21gr cells. Tungstate, either at nanomolar concentrations in nitrate media or at micromolar concentrations during growth in ammonium and nitrate induction, strongly decreased MoCo and NR amounts in wild‐type cells but had a slight effect in 21gr cells. Molybdate uptake activity of ammonium‐grown cells from both the wild‐type and 21gr strains was small and blocked by sulphate 0·3 mM. However, cells from nitrate medium showed a molybdate uptake activity insensitive to sulphate. This uptake activity was much higher and more sensitive to inhibition by tungstate in the wild type than in strain 21gr. These results suggest that strain 21gr has a high affinity and low capacity molybdate transport system able to discriminate efficiently tungstate, and lacks a high capacity molybdate/tungstate transport system, which operates in wild‐type cells upon nitrate induction. This high capacity molybdate transport system would account for both the stimulating effect of molybdate on MoCo amounts and the toxic effects of tungstate and molybdate when present at high concentrations.

Reactions of aromatic compounds with nucleophilic reagents in liquid ammonia: XVII. Effect of ionic association on the orientation in aryloxydefluorination of 2,4-difluoronitrobenzene

The analysis of dependence of fluorine replacement orientation in 2,4-difluoronitrobenzene effected by nucleophiles Y-C6H4OM (Y =p-OMe,p-Me,m-Me, H,p-F,p-Cl,m-F,m-Cl; M = Li, Na, K, Et4N, Bu4N) in liquid ammonia medium at -35‡C on the nature of M, Y, on nucleophile concentration, on addition of crown ethers, diaminoalkanes, and dimethoxyethane indicates the occurrence of ionic association at M = K, Na.

Effects of ammonia during different stages of culture on development of in vitro produced bovine embryos.

The effects of various concentrations of ammonia in the media during in vitro fertilization (IVF), culture (IVC), and throughout maturation (IVM), IVF, and IVC were evaluated using a randomized complete block design. Ammonia was added to the media at various concentrations during IVF (experiment 1), during IVC (experiment 2), and throughout IVM, IVF, and IVC (experiment 3). In the first experiment, there was a significant (P<0.05) increase in embryos developed to blastocyst, and to expanding and hatching blastocyst, in IVF media containing moderate concentrations of ammonia compared with that in the IVF control media. In the second experiment, ammonia in the IVC media increased (P<0.05) the proportion of degenerate ova and decreased (P<0.05) the proportion of ova that developed to blastocysts. In experiment 3, cleavage rates tended (P=0.06) to be greater for control groups than for treatment groups. The proportion of ova developing to morula was greater (P<0.05) in media containing moderate concentrations of ammonia than that in the control groups. These results indicate that the effect of ammonia on development of preimplantation bovine embryos depends on the concentration of ammonia and the stage of development when exposure to ammonia occurs.

Ni(II) and Cu(II) complexes with the dianionic N,N,O-tridentate Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone: Crystal structure of the monodimensionally hydrogen-bonded aqua-(6-amino-1,3-dimethyl-uracilato-benzoylhydrazone(2-)-N 6,N 51,O 52]-copper(II) hydrate

From the reaction between Cu(II) and Ni(II) salts and the Schiff base 6-amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone (H 2BEZDO), in dimethylformamide (DMF)–water and ammonia media, the complexes Ni(BEZDO)·H 2O·NH 3, Cu(BEZDO)·H 2O·NH 3 and [Cu(BEZDO)(H 2O)]·H 2O containing the dianionic organic ligand have been obtained. These compounds have been studied by IR, electronic and EPR spectroscopy and magnetic measurements. The structure of [Cu(BEZDO)(H 2O)]·H 2O has been solved by means of X-ray diffraction methods. The coordination environment around the Cu(II) may be described as a square-plane structure in which the Schiff base acts as tridentate ligand through the N(6), N(51) and O(52) atoms, making two five- and six-membered chelate rings. The coordination sphere is completed with the oxygen atom of a water molecule; any additional interactions with potential donor atoms in the axial direction have not been found. The crystal structure is formed by infinite hydrogen-bonded monodimensional chains, in which the nearest metal centres are at distances of 4.511 and 3.585 Å.

Effect of medium change on the development of in vitro matured and fertilized bovine oocytes cultured in medium containing amino acids.

Bovine in vitro matured and fertilized oocytes were cultured for 153 hr in groups of 3 or 30 in 30 microl of modified synthetic oviduct fluid medium supplemented with amino acids. The concentration of ammonium in culture medium at 153 hr of culture was significantly decreased by medium change at 72 hr of culture. However, regardless of embryo density, medium change had no beneficial or detrimental effect on the development of bovine embryos. Increase in the development to blastocysts and production of ammonium were observed when embryos were cultured in groups of 30. These results indicated that the ammonium concentration detected in this culture system has a negligible effect on the development of bovine embryos to blastocysts.

Cloning, sequencing, and expression of H.a.YNR1 and H.a.YNI1, encoding nitrate and nitrite reductases in the yeast Hansenula anomala.

A single Hansenula anomala genomic DNA fragment containing the genes H.a.YNR1 (yeast nitrate reductase) and H.a.YNI1 (yeast nitrite reductase) encoding nitrate and nitrite reductase, respectively, was isolated from a lambda EMBL3 genomic DNA library. As probe, a 3.2 kb DNA fragment isolated from a lambda gt11 H. anomala genomic DNA library screened with antiserum anti-NR from H. anomala was used. H. a.YNR1 and H.a.YNI1 genes are separated by 473 bp and encode putative proteins of 870 and 1077 amino acids, respectively, with great similarity to nitrate and nitrite reductases from other organisms. Northern blot analysis revealed that both genes are highly expressed in nitrate, very low in nitrate plus ammonium, and no expression was detected in ammonium or nitrogen-free media. Levels of nitrate reductase and nitrite reductase were very low or undetectable by Western blot analysis in nitrogen-free and ammonium media, whereas both proteins were present in nitrate and ammonium plus nitrate media. The nucleotide sequence Accession No. is AF123281.

Separation of carrier-free 199Au as a β-decay product of 199Pt

Carrier-free 199Au produced in neutron activated platinum as a β-decay product of 199Pt has been separated from bulk matrices through liquid–liquid extraction (LLX) using the liquid cation exchanger, di-(2-ethylhexyl) phosphoric acid (HDEHP), as an extractant for the target element from an aqueous ammonia medium. The effect of octanol on the extraction was also studied. Production, extent of separation and purity of the radiotracers at different stages of their LLX separation have been verified by taking recourse to γ-ray spectroscopy.

Oxygen reduction mechanisms at p-InP and p-GaAs electrodes in liquid ammonia in neutral buffered medium and acidic media

Abstract The use of buffered neutral liquid ammonia medium for the first time provided evidence for a current doubling effect on p-InP during oxygen photoreduction. Unlike results in aqueous medium, a common mechanism of O2 reduction was observed at p-InP and p-GaAs electrodes. When protons were added to the solution, two different oxygen reduction mechanisms occurred at these electrodes. This study emphasizes the important results of the hydrogenated p-InP surface and revealed that liquid ammonia (at 223 K) was perfectly appropriate to understand the mechanism of O2 reduction at InP electrodes.

An easy method for Ra-226 determination in river waters by liquid-scintillation counting

226Ra activity concentration in river water was determined using a low background liquid scintillation counter. Radium was extracted from the samples as Ra-BaSO4 precipitate which, afterwards, was dissolved with EDTA in ammonia medium. Solution was transferred into a low potassium glass vial and then mixed with a scintillation cocktail. Two different scintillation cocktails were selected for comparison. Efficiency, recovery yield and α/β separation were studied with both liquid scintillation cocktails. One single measurement, made one month after radium separation, allows to calculate the226Ra concentration as well as to assess the presence of alpha contamination of the sample. In the case of negligible interferences,224Ra concentrations can be subsequently evaluated in the same sample by the measurement made just after chemical separation of radium. This method has been applied for the determination of226Ra and224Ra activity concentrations in river water collected from different locations along the Odiel river estuary area (South-west of Spain). The presence of chemical industry, the wastes of which are released into the river, could be connected with radium activity concentration enhancements in the water.

CARACTERIZATION AND CATALYTIC BEHAVIOUR OF Cu/AlPO&lt;SUB&gt;4&lt;/SUB&gt; IN CO-NO CONVERSION

Samples of AlPO4 loaded with 2.5 and 5 wt% of copper were prepared by cations exchange in ammonia media, then characterized by TPR and U. V-visible spectroscopy. Copper was found on AlPO4 as an amine complex and also exchanged with the surface hydroxyls. The TPR profiles of the samples calcined at 500°C showed two peaks of H2 consumption.Catalysts efficiency in NO-CO conversion in presence of O2 was investigated. Both samples exhibited in CO oxidation an activity that reached 80 % at 350°C. NO reduction depended on the copper loading. The sample containing 5 % showed a conversion equal to 50 % at 430°C. The 2.5Cu/AlPO4 is less active.

Synthesis and Thermal Study of 8-Hydroxyquinoline Derivatives of the Alkaline Earth Metals I. Strontium Complexes

Strontium complexes of 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline were precipitated from an aqueous ammonia and acetone medium. The complexes obtained were Sr[(C9H4ONBr2)2]·2.5H2O; Sr[(C9H4ONCl2)(OH)]·1.5H2O; Sr[(C9H5ONI)2]·5H2O and Sr[(C9H4ONICl)(OH)]·1.25H2O. The residues of their thermal decomposition were SrBr2; a mixture of SrCl2, SrCO3 and SrO; SrCO3 and SrCO3, respectively. All were characterized by means of thermogravimetry, differential thermal analysis, complexometry with EDTA, atomic absorption spectroscopy, IR spectroscopy and X-ray diffraction.

Crescimento e parâmetros cinéticos de absorção de amônio e nitrato por mudas de Eucalyptus spp submetidas a diferentes relações amônio/nitrato na presença e ausência de fósforo

Com o objetivo de avaliar o efeito do fornecimento exclusivo de amônio ou de nitrato, ou de ambos, na presença e ausência de fósforo, sobre os parâmetros cinéticos de absorção destas formas de N e sobre o crescimento de mudas de eucalipto, foram desenvolvidos dois ensaios em casa de vegetação. No primeiro ensaio, foram utilizadas as espécies Eucalyptus urophylla e E. camaldulensis: e, no segundo, E. pellita, E. grandis e E. cloeziana: O crescimento inicial ocorreu em leito de areia lavada (32 dias) e, posteriormente, em solução nutritiva, em três relações amônio-nitrato (100-0, 50-50 e 0-100%) por 70 dias (ensaio 1) e 105 dias (ensaio 2). Após avaliação da altura, as plantas foram transferidas para câmara de crescimento onde permaneceram por 48 h em solução nutritiva isenta de nitrogênio (ensaio 1) ou com 0,36 mmol L-1 de N (ensaio 2). Após esse período, parte das plantas foi colhida para a determinação dos pesos de matéria seca de caule, folhas e raízes, enquanto parte foi submetida à exaustão de N num período de 10 h na presença ou ausência de P na solução nutritiva com 0,36 mmol L-1 de N. O fornecimento exclusivo de NO3- resultou em diminuição da altura e da produção de biomassa das plantas, à exceção do E. cloeziana, que mostrou maior crescimento com o aumento da concentração daquele ânion e morte de cerca de 80% das plantas, quando submetidas ao meio exclusivamente amoniacal. Excetuando E. cloeziana, maior proporção de nitrato no meio reduziu a relação biomassa de parte aérea/biomassa de raízes. Em meio nítrico, a ausência de P diminuiu drasticamente a eficiência de absorção de nitrato para E. grandis e E. pellita e pouco a modificou para o NH4+. Passando de um meio puramente nítrico ou amoniacal para um meio misto (amônio + nitrato), houve redução nos valores de Km-NH4+ e aumento para Km-NO3-.

Phenylalanine- and tyrosine-auxotrophic mutants of Saccharomyces cerevisiae impaired in transamination.

This paper reports the first isolation of Saccharomyces cerevisiae mutants lacking aromatic aminotransferase I activity (aro8), and of aro8 and aro9 double mutants which are auxotrophic for both phenylalanine and tyrosine, because the second mutation, aro9 affects aromatic aminotransferase II. Neither of the single mutants displays any nutritional requirement on minimal ammonia medium. In vitro, aromatic aminotransferase I is active not only with the aromatic amino acids, but also with methionine, alpha-aminoadipate, and leucine when phenylpyruvate is the amino acceptor, and in the reverse reactions with their oxo-acid analogues and phenylalanine as the amino donor. Its contribution amounts to half of the glutamate:2-oxoadipate activity detected in cell-free extracts and the enzyme might be identical to one of the two known alpha-aminoadipate aminotransferases. Aromatic aminotransferase I has properties of a general aminotransferase which, like several aminotransferases of Escherichia coli, may be able to play a role in several otherwise unrelated metabolic pathways. Aromatic aminotransferase II also has a broader substrate specificity than initially described. In particular, it is responsible for all the measured kynurenine aminotransferase activity. Mutants lacking this activity grow very slowly on kynurenine medium.

KINETICS OF CELL DEATH IN THE CYANOBACTERIUM ANABAENA FLOS‐AQUAE AND THE PRODUCTION OF DISSOLVED ORGANIC CARBON1

ABSTRACTKinetics of cell death and the production of dissolved organic carbon (DOC) were investigated in Anabaena flos‐aquae (Lyngb.) Bréb grown on three different N sources (N2nitrate, and ammonium) in a phosphorus (P)‐limited chemostat. The fraction of live cells in the total population increased as growth rate increased with decreasing P limitation. Cell death was less in nitrate and ammonium media than in N2. The specific death rate (γ), when calculated as the slope ofv−1x vs. D−1, where vxand D are live cell fraction (or cell viability) and dilution rate, respectively, was 0. 0082 day−1 in N2and 0.0042 day−1 in nitrate. The slope of the plot in ammonium culture was not significant; however, the value of the live cell fraction was within the range for the NO−3culture. The fraction of live vegetative cells in N2 culture was constant at all growth rates and the increase in the overall live cell fraction with growth rate was due entirely to an increase in live heterocysts. Live heterocysts comprised 3.5% of the total cells at a growth rate of 0.25 day−1 and increased to 6.3% at 0.75 day−1 with the ratio of live heterocysts to live vegetative cells linearly increasing with growth rate. The fraction of live vegetative cells was invariant in nitrate cultures us in N2cultures. The live heterocysts fraction also increased with growth rate in nitrate cultures, along with the live heterocysts : live vegetative cells ratio, but the level was lower than in N2cultures. DOC released from dead cells increased inversely with growth rate in N2from 36.4% of the total DOC at a growth rate of 0.75 day−1 to 54.15% at 0.25 day−1. The contribution of cell death to the total DOC production in nitrate and ammonium media was significantly less than that under N2DOC from dead cells consisted mainly of high‐molecular‐weight compounds, whereas DOC excreted from live cells was largely of low molecular weight.

Gas nitriding in catalytically prepared ammonia media

Chemical heat treatment of machine parts and tools in gas media at 500–600°C is widely used in the industry. However, the obvious advantages of the method are accompanied by certain serious disadvantages that reduce the range of its application. The present work is an attempt to realize a new approach to gas nitriding, solve some problems of the process, and widen the field of its application.

Physiological regulation of membrane protein sorting late in the secretory pathway of Saccharomyces cerevisiae.

In mammalian cells, extracellular signals can regulate the delivery of particular proteins to the plasma membrane. We have discovered a novel example of regulated protein sorting in the late secretory pathway of Saccharomyces cerevisiae. In yeast cells grown on either ammonia or urea medium, the general amino acid permease (Gap1p) is transported from the Golgi complex to the plasma membrane, whereas, in cells grown on glutamate medium, Gap1p is transported from the Golgi to the vacuole. We have also found that sorting of Gap1p in the Golgi is controlled by SEC13, a gene previously shown to encode a component of the COPII vesicle coat. In sec13 mutants grown on ammonia, Gap1p is transported from the Golgi to the vacuole, instead of to the plasma membrane. Deletion of PEP12, a gene required for vesicular transport from the Golgi to the prevacuolar compartment, counteracts the effect of the sec13 mutation and partially restores Gap1p transport to the plasma membrane. Together, these studies demonstrate that both a nitrogen-sensing mechanism and Sec13p control Gap1p transport from the Golgi to the plasma membrane.

Degradation of pentachlorophenol by the white rot fungus Phanerochaete chrysosporium grown in ammonium lignosulphonate media.

Removal and degradation of pentachlorophenol (PCP) by Phanerochaete chrysosporium in static flask cultures was studied using ammonium lignosulphonates (LS), a waste product of the papermill industry, as a carbon and nitrogen source. After 3 days, cultures of P. chrysosporium grown in either a 2% LS (nitrogen-sufficient) medium or a 0.23% LS and 2% glucose (nitrogen-deficient) medium removed 72 to 75% of PCP, slightly less than the 95% removal seen using nitrogen-deficient glucose and ammonia medium. PCP dehalogenation occurred despite the fact that extracellular enzyme (LiP) activity, measured by a veratryl alcohol oxidation assay and by PCP disappearance in cell-free extracts, was inhibited by LS. This inactivation of LiP likely contributed to the lower percent of PCP dehalogenation observed using the LS media. In order to better understand the relationship between PCP disappearance and dehalogenation, we measured the fate of the chlorine in PCP. After 13 days, only 1.8% of the initial PCP added was recoverable as PCP. The remainder of the PCP was either mineralized or transformed to breakdown intermediates collectively identified as organic halides. The largest fraction of the original chlorine (58%) was recovered as organic (non-PCP) halide, most of which (73%) was associated with the cell mass. Of the remaining chlorine, 40% was released as chloride ion, indicating a level of dehalogenation in agreement with previously reported values.

Constitutive expression of nitrate reductase changes the regulation of nitrate and nitrite transporters in Chlamydomonas reinhardtii

SummaryThe effect of constitutive expression of nitrate reductase (NR) on the regulation pattern of nitrite and nitrate transporters (NT) has been analysed in Chlamydomonas reinhardtii. Strain Tx11‐8, bearing the chimeric Nia1 gene for NR under the control of the cabll‐1 gene promoter, showed a constitutive NR which was inactive in ammonium‐grown cells. In contrast to the wild‐type, incubation of Tx11‐8 in ammonium media containing nitrate at micromolar concentrations resulted in reactivation of inactive NR and excretion of nitrite. In addition, negligible amounts of NT gene transcripts were induced by nitrate in this strain. However, NT transcripts from Tx11‐8 cells were induced in amounts similar to those in the wild‐type, by preventing constitutive NR expression from the cabll‐1 gene promoter in the dark. Strains lacking high‐affinity NT and nitrite reductase activity and having the chimeric Nia1 gene have been constructed by genetic crosses. All these strains were sensitive to chlorate in ammonium‐containing media and excreted nitrite when nitrate was present at millimolar concentrations. Spontaneous chlorate‐resistant mutants isolated from these strains lacked constitutive NR activity though they constitutively expressed NR mRNA. The data strongly suggest that nitrate plays an important post‐transcriptional regulatory role and that NR is involved in the regulation of the nitrate/ nitrite transport activities in C. reinhardtii.

ChemInform Abstract: Difference in the Results of Reductive Defluorination of Pentafluorobenzoic Acid by Sodium and Zinc in Liquid Ammonia Medium.

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On the difference in the results of reductive defluorination of pentafluorobenzoic acid by sodium and zinc in liquid ammonia medium

Under the reduction of pentafluorobenzoic acid in liquid ammonia by sodium the deep defluorination with removal of three or more fluorine atoms has been observed, whereas with zinc only the product of para-defluorination has been obtained.