Topic
Ammonia
About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.
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TL;DR: Penicillium chrysogenum will grow on methylamine (methylammonium chloride) as its sole nitrogen source and the permease is subject to feedback inhibition by intracellular glutamine and asparagine, and the original development of transport activity could result from derepression.
155 citations
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TL;DR: Myeloperoxidase was isolated from leucocytes obtained from the blood of patients suffering from chronic granulocytic leukaemia and was homogeneous in ultracentrifuge and free boundary electrophoresis.
Abstract: Myeloperoxidase was isolated from leucocytes obtained from the blood of patients suffering from chronic granulocytic leukaemia. The enzyme was purified 850 fold and was homogeneous in ultracentrifuge and free boundary electrophoresis. The molecular weight of the enzyme was found to be about 160,000.
The enzyme forms a spectrally characteristic complex with hydrogen peroxide with absorption maximum at 458 mμ. The spectrum of the native enzyme has absorption maxima at 430 and 570 mμ. The reduced enzyme is characterized by a spectrum with absorption maxima at 472 and 637 mμ.
The investigated myeloperoxidase catalysed oxidation of amino acids by hydrogen peroxide. Products of the oxidation of amino acids were ammonia, carbon dioxide, and an aldehyde corresponding to the oxidized amino acid. The observed reaction of deamination and decarboxylation is activated by chloride ions. In the presence of the chloride ions the optimum of the reaction is shifted toward the higher pH values.
The velocity of the reaction was found to be dependent on the concentration of the amino acid studied. Km values for various amino acids increased in the range 3.4 × 10−4 to 10−3 M in proportion to rising hydrophobic properties of the substrates. Taurine was found to be a competitive inhibitor in the examined reaction, and Ki values were in the range of 2 to 3 × 10−4 M, for different amino acids.
154 citations
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TL;DR: In this article, a combination of dielectric barrier discharge plasma and a monolithic V2O5-WO3/TiO2 catalyst using ammonia as a reducing agent was studied in synthetic gas mixtures at temperatures between 100 and 250°C.
Abstract: The selective catalytic reduction (SCR) of nitrogen oxides (NOx) by a combination of dielectric barrier discharge plasma and a monolithic V2O5-WO3/TiO2 catalyst using ammonia as a reducing agent was studied in synthetic gas mixtures at temperatures between 100 and 250°C. The mixtures were similar to diesel exhaust gases. For gas mixtures (NOx,0=NH3,0=500 ppm) in which 95% of the nitrogen oxides were in the form of NO, the removal of NOx below 140°C without plasma treatment was negligible. Treating the gas mixture with dielectric barrier discharges before the catalytic conversion, about 70% of the NOx was reduced at temperatures as low as 100°C. By plasma treatment 170 ppm of the NO was converted, 110 ppm by oxidation to NO2 and 60 ppm by reduction with products of NH3. Due to the coexistence of NO and NO2 on the catalyst, the selective catalytic reduction was enhanced. Similar effects were observed for the selective catalytic reduction in gas mixtures containing equal amounts of NO and NO2 without plasma treatment. Relative reaction rates for different NOx-reducing reactions over the catalyst are evaluated using a macroscopic model.
154 citations
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TL;DR: In this paper, a method for the determination of ammonia and nitrate in soil is described, which is applicable to coloured extracts and is not affected by substances found to interfere with other methods of determining ammonia and Nitrate.
Abstract: 1. Methods for the determination of ammonia and nitrate in soil are described. The ammonia and nitrate are extracted at pH 1·0–1·5 with a mixture of potassium sulphate and sulphuric acid, and the ammonia is determined by distillation with magnesium oxide at 25° C. in a modified Conway microdiffusion unit. Ammonia plus nitrate is determined on a separate sample of the same extract by reduction of the nitrate to ammonia with titanous hydroxide and subsequent distillation with magnesium oxide, both the reduction and distillation being carried out in a modified microdiffusion unit at 25° C.2. The methods are applicable to coloured extracts and are not affected by substances found to interfere with other methods of determining ammonia and nitrate.3. It is suggested that the methods may also prove useful for the determination of ammonia and nitrate in plant materials.
154 citations
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TL;DR: In this article, the reduction of nitric oxide with propane over alumina or HZSM-5 zeolite is investigated under various reaction conditions and it is found that the presence of oxygen is essential for selective reduction to occur.
154 citations