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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The capacity of bovine serum amineoxidase (SAO) to oxidize free amino groups of nonconventional substrates, such as polylysine (up to 50 kDa) and some proteins as lysozyme and ribonuclease A, is described. The oxidation was quantified from the amount of H2O2 and NH3 enzymatically produced by SAO. Kinetic analysis indicated a stereospecific preference for L-configuration. Maximal oxidation rate was obtained with poly-L-lysine (9.6 kDa). After 10 h of incubation at 37 degrees C, the poly-L-lysine was partially oxidized generating 1.5 moles of H2O2 by one mole of polylysine. Denatured SAO presented very low oxidation rates with the mentioned substrates.
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PMID:Extended substrate specificity of serum amine oxidase: possible involvement in protein posttranslational modification. 866 Mar 85

The objective of this study was to assess fermentation product, growth rate and growth yield responses of Selenomonas ruminantium HD4 to limiting and non-limiting ammonia concentrations. The ammonia half-inhibition constant for S. ruminantium in batch culture was 296 mM. Cells were grown in continuous culture with a defined ascorbate-reduced basal medium containing either 0.5, 5, 25, 50, 100 or 200 mM NH4Cl and dilution rates were 0.07, 0.14, 0.24 or 0.40 h-1. Ammonia was the growth-limiting nutrient when 0.5 mM NH4Cl was provided and the half-saturation constant was 72 microM. Specific rates of glucose utilization and fermentation acid carbon formation were highest for 0.5 mM NH4Cl. Lactate production (moles per mole of glucose disappearing) increased at the fastest dilution rate (0.40 h-1) for 5.0 mM NH4Cl while acetate and propionate decreased when compared to slower dilutions (0.07 and 0.14 h-1). Lactate production remained low while acetate and propionate remained high for all dilution rates when NH4Cl concentrations were 25 mM or greater. Yield (Y(Glc) and Y(ATP)) were nearly doubled when NH4Cl was increased from 0.5 mM (25.1 g cells/mol glucose used and 13.9 g cells/mol ATP produced respectively) to the higher concentrations. Y(Glc) was highest at 25 mM and 50 mM NH4Cl (48.2 cells/mol and 43.1 cells/mol respectively) as was Y(ATP) (23.2 cells/mol and 20.8 cells/mol respectively). Y(NH3) was highest at the lowest NH4Cl concentration. The maximal fermentation product formation rate occurred at a growth-limiting ammonia concentration, while maximal glucose and ATP bacterial yields occurred at non-growth-limiting ammonia concentrations. Given the growth response of this ruminal bacterium, it is possible that maximization of ruminal bacterial yield may necessitate sacrificing the substrate degradation rate and vice versa.
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PMID:Growth and fermentation responses of Selenomonas ruminantium to limiting and non-limiting concentrations of ammonium chloride. 898 47

Dry, excipient-free recombinant human tissue-type plasminogen activator (tPA) powder was prepared by lyophilization from ammonium bicarbonate solution. Ammonium bicarbonate sublimes into ammonia, water, and carbon dioxide upon lyophilization, without causing measurable harm to the protein. There were approximately 4 mol of residual ammonium ion per mole of lyophilized tPA. Under certain lyophilization conditions, a large pressure increase in the lyophilizer chamber occurred, presenting a pressure control problem. Microscopy and sublimation rate measurements on the frozen matrix revealed that ice sublimation occurred first, followed by the sublimation of ammonium bicarbonate. Analysis of the sectioned frozen matrix indicated that the bicarbonate salt was evenly distributed throughout the vial, suggesting that the delay of ammonium bicarbonate sublimation was not due to hindrance by ice. In the two-stage process, ice sublimation proceeded according to zero-order kinetics, whereas ammonium bicarbonate sublimation followed a grain-burning (2/ 3-order) model and was governed by a higher activation enthalpy. In most cases, the sublimation rate of ammonium bicarbonate in the presence of tPA was lower than that in the absence of the protein. Sublimation activation enthalpy for ammonium bicarbonate in the presence of tPA was 26.1 +/- 3.8 kcal/mol, which was approximately 10 kcal/mol greater than that for the tPA-free system. Consistent with a prediction from our kinetic modeling, a 6-h extension of primary drying enabled us to conduct lyophilization while maintaining pressure control.
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PMID:Preparation of excipient-free recombinant human tissue-type plasminogen activator by lyophilization from ammonium bicarbonate solution: an investigation of the two-stage sublimation phenomenon. 910 48

We report some characteristics of a ruminal bacterium (strain NPOH1) that metabolizes 3-nitropropanol, the toxic principle of various milk vetchs that are distributed worldwide. The gram-positive bacterium was nonmotile and did not produce spores. Growth of strain NPOH1 occurred under anaerobic conditions and was supported by the electron acceptors 3-nitropropanol, 3-nitropropionate, nitrate, 2-nitropropanol, nitroethane, nitroethanol, or 3-nitro-1-propyl-beta-D-glucopyranoside (miserotoxin). Other potential electron acceptors, namely sulfate, sulfite, azide, chlorate, perchlorate, nitrite, fumarate, 2-nitrobutane, or nitrobenzene, did not support growth. Formate, lactate, and H2 stimulated growth of strain NPOH1 in the presence of the appropriate nitrocompound, whereas a variety of other potential H2 donors did not. When grown in medium containing both nitrate and either 3-nitropropanol or 3-nitropropionate, nitrate was the preferred acceptor. Strain NPOH1 reduced nitrate to nitrite and, when grown with excess reductant, nitrite was further reduced to ammonia. The products formed during the metabolism of 3-nitropropanol and 3-nitropropionate by mixed ruminal populations, 3-aminopropanol and beta-alanine, were not found in culture fluids of strain NPOH1. Analysis of total cellular fatty acid profiles and of the mole percent guanine plus cytosine suggests that strain NPOH1 is a novel bacterium. The capacity of strain NPOH1 to metabolize 3-nitropropanol suggests that this organism may play an important role in detoxification of 3-nitropropanol in the rumen.
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PMID:Characteristics of a nitropropanol-metabolizing bacterium isolated from the rumen. 924 40

Chronic liver disease is often accompanied by hypoxaemia. We investigated the clinical factors that were related to the arterial oxygen tension (PaO2) in 40 women, all non-smokers with chronic liver disease. They were positive for hepatitis C virus (HCV) antibody and had no evidence of cardiopulmonary disease. Arterial blood was collected from patients at rest (> 15 min) for analysis of blood gases. We determined the correlation between blood gas tension and the clinical variables, i.e. the presence or absence of skin manifestations such as cutaneous spider nevi and palmar erythema, the presence or absence of splenomegaly, vital capacity, forced expiratory volume in one second, V25/body height, serum alanine aminotransferase (AST), serum asparate aminotransferase (ALT), serum cholinesterase, serum gamma-globulin/total protein, excretion of indocyanine green at 15 min (15-min retention rate, ICG level), blood level of ammonia, blood level of endotoxin, plasma level of glucagon and the serum level of type IV collagen-7S. The mean level of PaO2 was 78 +/- 11 (range: 43-95) torr. The mean alveolar-arterial oxygen tension gradient (A-aDO2) was 19 +/- 13 (range: 2-60) torr. Multiple regression analysis used PaO2 and A-aDO2 as objective variables, and the clinical findings as explanatory variables. The explanatory variables that were significantly correlated with blood gas values were ICG level, blood level of endotoxin and presence of skin manifestations. The ICG level showed a high correlation with blood gas values; the ICG level increased, the PaO2 decreased (r = -0.69), while the A-aDO2 showed a high positive correlation (r = +0.78, P < 0.001). Findings suggest that a reduction in hepatic blood flow and hepatocellular function interfere with the inactivation of vasoactive substances such as endotoxin by the liver, leading to the development of skin manifestations, the dilatation of intrapulmonary capillaries and the induction of hypoxaemia.
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PMID:Clinical factors that affect blood gases in non-smoking women with chronic liver disease. 951 26

Although glutamine is a major carbon source for mammalian cells in culture, its chemical decomposition or cellular metabolism leads to an undesirable excess of ammonia. This limits the shelf-life of glutamine-supplemented media and may reduce the cell yield under certain conditions. We have attempted to develop a less ammoniagenic medium for the growth of BHK-21 cells by a mole-to-mole substitution of glutamine by glutamate. This results in a medium that is thermally stable but unable to support an equivalent growth yield. However, supplementation of the glutamate-based medium with asparagine (3 mM) and a minimal level of glutamine (0.5 mM) restored the original growth capacity of the cultures. Substitution of the low level of glutamine with the glutamine dipeptides, ala-gln (1 mM), or gly-gln (3 mM) resulted in an equivalent cell yield and in a thermally stable medium. The ammonia accumulation in cultures with glutamate-based medium was reduced significantly (>60%). Factors mediating growth and adaptation in medium substituted with glutamate were also investigated. The maximum growth capacity of the BHK-21 cells in glutamate-based medium (without glutamine) was achieved after a period of adaptation of 5 culture passages from growth in glutamine-based cultures. Adaptation was not influenced by increases in glutamate uptake which was constitutively high in BHK cells. Adaptation was associated with changes in the activities of enzymes involved in glutamate or glutamine metabolism. The activities of glutamine synthetase (GS) and alanine aminotransferase (ALT) increased significantly and the activity of phosphate-activated glutaminase (PAG) decreased significantly. The activity of glutamate dehydrogenase (GDH) showed no significant change after adaptation to glutamate. These changes resulted in an altered metabolic profile which included a reduced ammonia production but an increased alanine production. Alanine production is suspected of being an alternative route for removal of excess nitrogen.
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PMID:The adaptation of BHK cells to a non-ammoniagenic glutamate-based culture medium. 1039 67

Model halogenated aromatic and aliphatic hydrocarbons and halogenated phenols were dehalogenated in seconds by solvated electrons generated from sodium in both anhydrous liquid ammonia and ammonia/water solutions. The minimum sodium required to completely dehalogenate these model compounds was determined by increasing the Na/substrate ratio until halogen loss was complete. Minimum sodium consumptions were determined in both anhydrous liquid ammonia and with a (5, 20, 50-fold molar excess of water per mole of halide). While more Na was consumed in the presence of water, these dehalogenations were still efficient when a 50-fold water excess was present. Dehalogenation is faster than competiting reactions with water. CCl4 and CH3CCl3 in the presence of a stoichiometric deficiency of sodium produced only CH4 and CH3CH3 and recovered CCl4 or CH3CCl3, respectively. No partially dechlorinated products were detected, indicating dechlorination was diffusion controlled. Na consumption per chlorine removed (as NaCl) was lower than that of Li, K or Ca and this advantage increased in the presence of water. Na consumption was lower using Na chunks instead of a thin Na mirror. Chloroaromatic compounds gave the parent aromatic hydrocarbon and aminated products in anhydrous ammonia but aminated products did not form when water was present.
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PMID:Destruction of halogenated hydrocarbons with solvated electrons in the presence of water. 1086 64

Results of experimental study of volume flux in one-membrane system were presented. This system contains horizontal, microporous and symmetrical flat polymeric membrane (Nephrophan), which separate water and electrolyte solution. As binary solutions, aqueous ammonia solutions, which density is lower than water density, were used. As ternary solutions the ammonia with KC1 (0.1 or 0.2 mole.l-1) in aqueous solution were used. The density of ternary solutions was lower, higher or the same as water density. Two configurations of membrane system (A and B) in gravitational field were studied. In configuration A, water was in compartment over the membrane and the solution was under the membrane. In configuration B the succession was reverse. The thermodynamic model of flux graviosmotic effect was elaborated, and the calculations of this effect were performed for A and B configurations of one membrane system. The experimental results are interpreted in terms of gravitational instability that reduces concentration boundary layer dimensions and increases the diffusion permeability coefficient value of the complex: boundary layer/membrane/boundary layer.
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PMID:Gravitational effects in the passive osmotic flows across polymeric membrane of electrolytic solutions. 1106 86

Excimer laser fragmentation-fluorescence spectroscopy (ELFFS) is shown to be an effective detection strategy for ammonium nitrate and ammonium sulfate particles at atmospheric pressure and room temperature. Following photofragmentation of the ammonium salt particle, fluorescence of the NH fragment is observed at 336 nm. The fluorescence signal is shown to depend linearly on particle surface area for laser intensities varying from 1.2 x 10(8) to 6 x 10(8) W/cm2. The 100 shot (1 s) detection limits for ammonium nitrate range from 20 ppb for 0.2 microm particles to 125 ppb for 0.8 microm particles, where these concentrations are expressed as moles of ammonium ion per mole of air. For ammonium sulfate, the 100 shot (1 s) detection limits vary from 60 ppb for 0.2 microm particles to 500 ppb for 1 microm particles. These detection limits are low enough to measure ammonium salt particles that form in the exhaust of combustion processes utilizing ammonia injection as a nitric oxide control strategy.
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PMID:Excimer laser fragmentation-fluorescence spectroscopy as a method for monitoring ammonium nitrate and ammonium sulfate particles. 1121 91

Low-pressure continuous-flow laboratory simulations of plasma induced chemistry in H2/He/CH4/NH3 atmospheres show radiation yields of hydrocarbons and nitrogen-containing organic compounds that increase with decreasing pressure in the range 2-200 mbar. Major products of these experiments that have been observed in the Jovian atmosphere are acetylene (C2H2), ethylene (C2H4), ethane (C2H6), hydrogen cyanide (HCN), propane (C3H8), and propyne (C3H4). Major products that have not yet been observed on Jupiter include acetonitrile (CH3CN), methylamine (CH3NH2), propene (C3H6), butane (C4H10), and butene (C4H8). Various other saturated and unsaturated hydrocarbons, as well as other amines and nitriles, are present in these experiments as minor products. We place upper limits of 10(6)-10(9) molecules cm-2 sec-1 on production rates of the major species from auroral chemistry in the Jovian stratosphere, and calculate stratospheric mole fraction contributions. This work shows that auroral processes may account for 10-100% of the total abundances of most observed organic species in the polar regions. Our experiments are consistent with models of Jovian polar stratospheric aerosol haze formation from polymerization of acetylene by secondary ultraviolet processing.
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PMID:Radiation chemistry in the Jovian stratosphere: laboratory simulations. 1154 Jan 56


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