Ammonia In Medium Research Articles

Chemiluminescence determination of tetracyclines based on their reaction with hydrogen peroxide catalysed by the copper ion

A flow injection-based method for the determination of tetracycline, chlortetracycline and oxytetracycline has been proposed. It is based on the reaction of the tetracyclines with hydrogen peroxide, catalysed by the copper ion in ammonia medium. Persulfate was used as a co-oxidizing agent. The procedure allows the determination of 0.025–2.5 nmol of chlortetracycline and 0.25–25 nmol of tetracycline and oxytetracycline (50 µl per injection) by the flow-injection method compared with 0.005–50 µmol l–1 of chlortetracycline and 0.05–500 µmol l–1 of tetracycline and oxytetracycline by the classical batch method. The method is sensitive, selective and easy to operate and can be used for the determination of tetracyclines in pharmaceutical preparations. A discussion on the possible reaction mechanism is presented.

Spectrophotometric determination of trace copper with a Cu-diethyldithiocarbamate-β-cyclodextrin colour system

A simple, selective and accurate spectrophotometric method for determination of trace copper with diethyldithiocarbamate(DDTC) in the presence of β-cyclodextrin(β-CD) in ammonia media has been developed. The apparent molar absorptivity of Cu(II)-DDTC-β-CD inclusion complex is 1.3 × 10 4 1 · mole −1 · cm −1 at 436 nm, and Beer's law is obeyed for copper in the range 0–150 μg/25 ml. The detection limit is 4.38 × 10 −7 M( S/ N = 3). The proposed method has been successfully applied to the determination of copper in aluminium alloys, soils, millet, wheat flour, herbs, vegetables and some traditional Chinese herbal medicines with satisfactory results.

Causes of failure of heat-resistant steel piping in Parex-1 units

One of the causes of equipment failures in petroleum refineries is the nitriding of steels in ammonia media at high temperatures and pressures. At 350-600~ ammonia dissociates into hydrogen and nitrogen. The nitrogen, diffusing into the metal, forms brittle nitride layers that are susceptible to cracking in the course of long-term service. The process of saturation with nitrogen depends on the chemical composition of the steel, the temperature, and the duration of surface heating of the equipment. The dissociation constant of ammonia increases with increasing temperature, and the nitrogen saturation process is accelerated [1]. In the Parex-1 unit at the Kirishi Petroleum Refinery, after 10 years of operation, failures were noted in type KhM [chromium-molybdenum] heat-resisting steel pipelines carrying ammonia-containing media. These pipelines operate at 380400~ under a pressure of 1.8 MPa, so that we must assume the possibility of nitriding. Metallographic examinations to determine the causes of the pipeline failures were performed with a Neophot microscope (East Germany), on specimens cut from different sections of the piping (see Table 1). It was established that the pipelines transporting the desorbate and denormalizate were nitrided on the inside. The nitrided zone consisted of needles of a 7-phase (iron and chromium nitrates), segregated in the volume of grains of the c~-solution (Fig. 1). The brittle nitrided layer was susceptible to failure (Fig. 2). The depth of saturated nitrided layer, as revealed by microstructural analysis, was 0.8-1.4 and 0.5 mm, respectively, for the pipelines transporting desorbate and denormalizate. On the specimens cut from the pipelines transporting purge gas and gaseous feed mixture, no nitrided layer could be detected by microstructural analysis. The concentration of nitrogen varied through the thickness of the nitrided layer. The actual thickness of the layer could not be determined by microstructural analysis; the thickness was generally greater than the thickness of the diffusion layer as determined on the basis of the two-phase zone e~ + 3''. Therefore, we investigated the possibility of determining the thickness of the nitrided layer by means of layer-by-layer measurements of microhardness in a Microdur instrument manufactured by Krautkrfimer (East Germany). It can be seen from Fig. 3 that, for the specimens from the pipelines transporting desorbate and denormalizate, the maximum hardness (HB 400-700) is observed at depths up to 1 mm from the inner surface of the pipe; this is consistent with the thickness of the saturated nitrided layer (c~ + 3'') as determined metallographicalty. The greater hardness that is observed all the way to a depth of 4-5 mm indicates the presence of nitrogen dissolved in the a-phase at this depth.

Stimulation of dark carbon fixation in rice and tomato roots by application of ammonium nitrogen

Abstract Dark carbon fixation was investigated in roots of rice plants, an ammonium-tolerant species and tomato plants, an ammonium-sensitive one during periods of growth on nutrient media containing ammonium, ammonium nitrate, or nitrate as the nitrogen source. Application of ammonium nitrogen immediately stimulated the dark carbon fixation in the roots of both plants. The stimulation was greater in the plants grown on ammonium media than in those grown on ammonium nitrate media. The increase in the rates of dark carbon fixation continued in rice plants for 7 d whereas in tomato plants the rates reached the maximum value at day 1, and then gradually decreased. Most of the 14C fixed for 3 h remained in the roots: 75–90% in rice plants and 65–80% in tomato roots. Soluble fixation products were composed of amino acids and organic acids. Organic acids were more labelled than amino acids. Amino acids were more labelled in both plants grown on ammonium and ammonium nitrate media than in those grown on nitrate ...

Metabolism of 15N-labelled ammonium by the ectomycorrhizal fungus Pisolithus tinctorim (Pers.) Coker & Couch

Glutamine was the major product accumulated following transfer of nitrogen-limited cultures of the ectomycorrhizal fungus Pisolithus tinctorius to an ammonium medium. Experiments in which mycelium was transferred to [15N]H4+showed glutamine amide was the most heavily labelled product. Assimilation of ammonium into glutamate was markedly inhibited by azaserine. The kinetics of 15N-labelling and the effects of azaserine and methionine sulphoximine on the distribution of 15N-labelled products are entirely consistent with the operation of the glutamate synthase cycle. No evidence was found for ammonium assimilation via glutamate dehydrogenase. The labelling pattern observed in mycelium treated with aminooxyacetate suggests that transamination reactions are an important source of glutamate for the synthesis of glutamine.

Synthesis of p-Azobenzenediazoaminoazobbnzene Sulfonic Acid and its Application for Spectrophotometric Determination of Cadmium

The synthesis and characteristics of a new chromogenic reagent p-azobenzenediazoaminoazobenzene sulfonic acid (ADAAS) is reported. ADAAS forms a dark-violet red complex with cadmium in the presence of Triton X-100 and in ammonia medium. The molar absorptivity of the complex is 2.02 {times} 10{sup 5} 1 mol{sup {minus}1} cm{sup {minus}1} at 532 nm, and the formation constant of the complex is 6 {times} 10{sup 21}. Beer's law is obeyed for cadmium concentrations of between 3.6 {times} 10{sup {minus}8} M and 4.3 {times} 10{sup {minus}6} M. The effect of foreign ion can been eliminated completely by use of masking agents. The proposed method has been used for the determination of trace amounts of cadmium in water samples.

Phase composition and formation of cobalt-copper cement catalysts

Using x-ray phase analysis, DTA, DTG, and temperature-programmed reduction, we have studied the phase composition and formation of cobalt-copper cement catalysts obtained by chemical mixing of hydroxocarbonates of cobalt (CoHC) and copper (CuHC) with the aluminocalcium cement talyum, consisting of CaAl2O4 and CaAl4O7, in an aqueous ammonia medium. We have shown that when the components are mixed, exchange reactions occur with development of new phases of cobalt and copper hydroxoaluminates, calcite, gibbsite, Cu(OH)2, CuO. We found that CaAl2O4 is more reactive than CaAl4O7. We have obtained data on the change in the phase composition upon thermolysis and reduction in H2.

Minimal Requirements for Growth of Brucella suis and Other Brucella Species

Minimal nutritional requirements and temperature limits of growth were studied in Brucella suis and, comparatively, in a few other Brucella species. In a saline basic medium including thiosulphate, ammonium sulphate and glucose with addition of 2 or 4 vitamins (nicotinic acid, thiamin and panthotenic acid, biotin), 24 out of 25 B. suis, 4/6 B. melitensis and 1/6 B. abortus strains were able to grow. Some strains, however, needed to be initially induced to grow by other ingredients, CO2, other vitamins, or amino acids, or by a prolonged incubation. In the saline basic medium without ammonium, glutamic acid and/or alanine and arginine, with or without glucose, supported the growth of all the B. suis and B. melitensis strains, except 2 which required a sulphur amino acid. Five out of 6 B. abortus strains did not grow in either medium without addition of one or several aromatic amino acids or, for one strain, aspartic acid, or valine. One strain could also be induced to grow in ammonium medium by other amino acids. In a rich medium with yeast extract, all Brucella species grew at 18 degrees C and 42.5 degrees (except one) while most B. suis (14/17) grew also at 15 degrees C and 44 degrees C, in contrast to other brucellae of which a few strains only grew at these temperatures. In saline ammonium glucose medium, yeast extract at 0.1 g/l provided all the required vitamins and amino acids for all brucellae and at 1 g/l, it even provided enough nitrogen to support growth without ammonium. Such basic saline medium with yeast extract may be advantageously used in routine Brucella culture, instead of the classic undefined peptone mediums. B. suis biovar 1 strains did not differ significantly in their minimal nutritional requirements, precluding the use of these requirements to differentiate the strains, in particular the Chinese vaccine strain S2 from the reference strain 1330 or from other strains from different parts of the world. Finally, B. suis which is endowed with a nearly complete synthetic potential may represent the parental Brucella species from which the melitensis and abortus species may have evolved.

Toxic Effects of Manure, Alfalfa, and Ammonia on Emergence and Growth of Cucumber Seedlings

Chopped alfalfa (Medicago sativa L.), alfalfa hay extract, and ammonium hydroxide produced free ammonia in media and inhibited both germination and seedling growth of cucumber (Cucumis sativus L.). Toxic levels of ammonia were not produced by the quantities of manure added to the media. Alfalfa extract enhanced cucumber seedling growth in sand medium while inhibiting growth in sand-soil media. This difference is attributed to a reduced level of microbial activity in the sand. With higher levels of microbial activity, rapid decomposition of the extract may have resulted in a burst of ammonia evolution that proved damaging to cucumbers. The natural buffering capacity of the soil medium apparently mitigated the effects of the ammonia. Ammonium hydroxide, which did not depend on microbiological activity to release ammonia, proved lethal to cucumbers grown in sand. A diminished effect on growth was observed as the cation exchange capacity of the medium increased. Because high levels of alfalfa hay and ammonium hydroxide were required to produce toxic levels of ammonia in soil, it is unlikely that cucumbers would be harmed under normal field usage of alfalfa hay.

Regulation of molybdenum cofactor species in the green alga Chlamydomonas reinhardtii

Molybdenum cofactor (MoCo) of molybdoenzymes is constitutively produced in cells of the green alga Chlamydomonas reinhardtii grown in ammonium media, under which conditions certain molybdoenzymes are not synthesized. In soluble form, MoCo was found to be present in several forms: (i) as a low Mr free species; (ii) bound to a MoCo-carrier protein of about 50 kDa that could release MoCo to directly reconstitute in vitro nitrate reductase activity in the nit-1 mutant of Neurospora crassa, but not to Thiol-Sepharose which, in contrast, bonded free MoCo; and (iii) bound to other proteins, putatively constitutive molybdoenzymes, which only released MoCo after a denaturing treatment. The amount of total MoCo (free, carrier-bound and heat releasable forms) was dependent on the growth phase of cell cultures. Constitutive levels of total MoCo in ammonium-grown cells markedly increased when cells were transferred to media lacking ammonium (nitrate, urea or nitrogen-free media). This increase did not require de novo protein synthesis and was stimulated by light. Levels of both total MoCo and free plus carrier-bound MoCo seemed to be unrelated to either nitrate reductase synthesis or functioning of nit-1 and nit-2 genes responsible for nitrate reductase structure and regulation, respectively. Results suggest that MoCo is continuously synthesized in C. reinhardtii and that its levels are regulated by ammonium in a way independent of nitrate reductase synthesis.

Extracellular ferricyanide reduction and nitrate reductase activity in the green alga Monoraphidium braunii

The unicellular green alga, Monoraphidium braunii, reduced extracellular ferricyanide at high rates. Impermeability of the membranes to ferri- and ferrocyanide was shown for untreated cells as for those permeabilized with 5% 1-propanol. Fe starvation stimulated reduction rates by 50%, light or glucose were ineffective. Extracellular acidification largely corresponded to formation of the new anionic valence of ferrocyanide. 1-Propanol used as permeabilizer for NR assays in the same samples apparently inhibited ferricyanide reduction, however addition of catalase showed that this was not due to interference with ferricyanide reduction but to partial reoxidation by H 2O 2. Between ferricyanide reduction and nitrate reduction no competitionwas found in an ‘in situ’ system with endogenous reductant in the presence of 1-propanol, neither with ‘induced’ algae showing high NR activity nor with ‘repressed’ algae grown in ammonium medium and showing only constitutive NR activity. According to this data the inducible high-activity NR and the inducible nitrate uptake system are not responsible for reduction of ferricyanide. The plasmalemma-bound, low activity, NR might have extracellular reducing activity, but also for this NR lack of competition in reduction of the two substrates indicated independent reactions in Monoraphidium.

Investigation of the distribution of acidity strength in zeolites by temperature-programmed desorption of probe molecules. 2. Dealuminated Y-type zeolites

The acidity of dealuminated hydrogen forms of Y-type zeolites (Si/Al = 2.4-8.6) is determined by temperature-programmed desorption of ammonia or pyridine, which is monitored through a mass spectrometer. Four types of acidic sites are indicated by ammonia, viz., weak Broensted and/or Lewis centers and medium and strong Broensted and strong Lewis sites. In contrast, pyridine, after sample activation at 675 K, probed only two types of sites, i.e., medium and strong Broensted sites. This difference is ascribed to different accessibility of sites for the two probe molecules. From the desorption spectra (i) the fractional coverage of the various sites, (ii) the most frequent energies of activation, {anti E}{sub d}, for desorption, and (iii) the probability functions of the activation energies are derived by using a previously described method of evaluation.

Spectrophotometric Assay of Certain Aminoglycosides Using Cyanoacetamide

Abstract A simple and sensitive ultraviolet spectrophotometric method has been devised for the determination of amikacin, kanamycin, neomycin and streptomycin in pure form and in some pharmaceutical preparations. The method depends on the nitrosation of the primary amino groups followed by reaction with cyanoacetamide in ammonia medium at 100°C for 30 min, The reaction products exhibit a characteristic absorption. maximum at 270 nm. Beer's law is obeyed within the concentration ranges 4–40 μg ml−1 for amikacin, kanamycin and neomycin and 8–80 μg ml−1 for streptomycin with apparent molar absorptivities of about 1.85 × 104 for the first three compounds and 1.3×104 1. mole−1.cm−1 for streptomycin.

Effect of nitrate and ammonium nutrition on the metabolism of the ectomycorrhizal basidiomycete, Hebeloma cylindrosporum Romagn

SUMMARY Hebeloma cylindrosporum Romagn. grown on a nitrate medium exhibits a growth rate ten times greater than that on an ammonium medium lacking organic acids. Nitrate reduction is accompanied by a low rate of synthesis of organic anions and an elevated excretion of OH− ions into the external medium. The addition of a Krebs cycle organic acid, e.g., malate, citrate, succinate or pyruvate to the ammonium medium induces a strong increase in the growth of the thalli which then equals that obtained on a nitrate medium. The absorption of such precursors to 2‐oxoglutarate could permit the recharging of the Krebs cycle, otherwise inhibited because the assimilation of ammonium causes an important re‐routing of 2‐oxoglutarate. In these thalli, the soluble nitrogen content shows a clear reduction compared with the thalli cultured on ammonium medium lacking organic acids. The poor growth observed on an ammonium medium may be due in part to insufficient CO2 fixation by anaplerotic reactions which, in Hebeloma cylindrosporum Romagn., is carried out by phosphoenolpyruvate carboxykinase.

Stable nuclear transformation of Chlamydomonas using the Chlamydomonas gene for nitrate reductase.

We have developed a nuclear transformation system for Chlamydomonas reinhardtii, using micro-projectile bombardment to introduce the gene encoding nitrate reductase into a nit1 mutant strain which lacks nitrate reductase activity. By using either supercoiled or linear plasmid DNA, transformants were recovered consistently at a low efficiency, on the order of 15 transformants per microgram of plasmid DNA. In all cases the transforming DNA was integrated into the nuclear genome, usually in multiple copies. Most of the introduced copies were genetically linked to each other, and they were unlinked to the original nit1 locus. The transforming DNA and nit+ phenotype were stable through mitosis and meiosis, even in the absence of selection. nit1 transcripts of various sizes were expressed at levels equal to or greater than those in wild-type nit+ strains. In most transformants, nitrate reductase enzyme activity was expressed at approximately wild-type levels. In all transformants, nit1 mRNA and nitrate reductase enzyme activity were repressed in cells grown on ammonium medium, showing that expression of the integrated nit1 genes was regulated normally. When a second plasmid with a nonselectable gene was bombarded into the cells along with the nit1 gene, transformants carrying DNA from both plasmids were recovered. In some cases, expression of the unselected gene could be detected. With the advent of nuclear transformation in Chlamydomonas, it becomes the first photosynthetic organism in which both the nuclear and chloroplast compartments can be transformed.

Two different carriers transport both ammonium and methylammonium in Chlamydomonas reinhardtii.

A new methylammonium-resistant mutant strain from Chlamydomonas reinhardtii, henceforth termed 2172 (ma-2), has been isolated. This mutant is affected in a single mendelian gene different from and linked to the ma-1 locus which is defective in the methylammonium-resistant mutant 2170. Both mutations in ma-1 (2170) and ma-2 (2172) are linked to the nit-1 gene coding for the nitrate reductase apoenzyme. Mutant 2172 is affected in methylammonium but not in ammonium uptake capacity and shows derepressed nitrate and nitrite reductase activities in media containing nitrate plus methylammonium but not in nitrate plus ammonium media. The following two enzymatic components for the transport of both ammonium and methylammonium in wild-type cells have been identified: component 1, with high Vmax and K values, which is constitutive, and component 2, with low Vmax and K values, which is ammonium-repressible. Mutant 2170 lacks component 1 whereas mutant 2172 lacks component 2 for both methylammonium and ammonium transport. From genetic and kinetic evidences we conclude that in C. reinhardtii two different carriers are responsible for the transport of both ammonium and methylammonium and that methylammonium (ammonium) transport is a reversible process probably inhibited by the intracellular ammonium which, in turn, regulates nitrate and nitrite reductase levels.

Synthesis of Phthalaldehyde Bisguanylhydrazone (PABGH). Spectrophotometric Analysis of Co(II)-Cu(II)-Ni(II) Mixtures in the Presence of Several Cations

Abstract The synthesis and analytical properties of phthalaldehyde. bisguanylhydrazone (PABGH) are described. The reagent was tested with 34-common cations, at several pH values, but only Co(II), Cu(II), Ni(II) gave colored reactions. The Co(II), Cu(II) complexes are formed in ammonia medium and only the Co(II) complex is stable in the presence of cyanide. The Ni(II) complex is formed in sodium hydroxide medium. Using these behaviors the Co(II)-Cu(II)-Ni(II) mixtures can be analyzed by spectrophotometry in the presence of the remaining tested cations.

Spectrophotometric determination of hydroxylamine using the DPGH-iron(II)-NH 2OH ternary complex

Iron(II) reacts with di(2-pyridyl)ketone guanylhydrazone in ammonia medium to form a yellow complex. This complex is decolorized by the addition of sodium hydroxide but in the presence of hydroxylamine a stable blue-colored complex is formed. Based on these properties a method was developed for the spectrophotometric determination of hydroxylamine in the presence of other reducing substances.

Spectrophotometric Determination of Periodate by Means of 2-Hydroxybenzaldehyde Guanylhydrazone (2-HBGH)

Abstract Periodate oxidizes 2-HBGH to a red colored compound in ammonia medium. The reagent is not oxidized by H2O2, IO3 −, BrO3 −, S2O8 =, S2O5 =, ClO4 −, ClO3 − under these conditions. Based on the above properties a method is described for the spectrophotometric determination of periodate.

Isolation of the NPR1 gene responsible for the reactivation of ammonia-sensitive amino-acid permeases in Saccharomyces cerevisiae. RNA analysis and gene dosage effects.

The NPR1 gene codes for a protein, called the nitrogen permease reactivator protein or Npr1, which appears to promote the activity of several permeases for nitrogenous substances under conditions of nitrogen catabolite derepression, but fails to do so in the presence of ammonium ions. This gene has been cloned. Its transcription seems unaffected by growth on ammonia, so any ammonia regulation of Npr1 function most likely occurs at another level. In order to elucidate further the mechanism of permease inactivation, which requires an intact NPI1 gene product (NPI1 for nitrogen permease inactivator gene, formerly termed MUT2) and the role of Npr1 in counteracting this process, we have studied the effects of NPR1 and NPI1 gene dosage on general amino-acid permease activity. On nitrogen-derepressing media, NPR1 gene dose can be increased from 1 copy in a diploid to 16 plasmid-borne copies in a haploid strain without altering general amino-acid permease activity. On minimal ammonia medium, the plasmid-bearing haploid cells exhibit low but increased general amino-acid permease activity with respect to non-transformed cells. The adverse effect of the NPI1 gene product on general amino-acid permease activity is reduced when NPI1 gene dose is decreased to 1 gene copy in a diploid strain, regardless of the nitrogen source. We hypothesize that this product inactivates the permease by stoichiometric binding and that the Npr1 protein or a product of its catalytic action opposes this binding under conditions of nitrogen derepression.