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At least 487 records · Page 27Linked to original sources
PubMed1975

Thin-layer gel chromatography of dyed proteins.

Plasma chromatography as a method for ultratrace qualitative and quantitative detection of organic compounds is especially well suited for detection of gas chromatographic effluents. The optimum range of sample quantity is 10(-6) to 10(-12) g for detection and identification of a compound by use of its characteristic positive and negative mobility spectra. The type of reference mobility spectra produced by alkanes, aromatics, esters, halogenated compounds, nitrogenated compounds and organic acids have been previously reported. This study presents the reference mobility spectra produced for lysergic acid diethylamide (LSD), delta9-tetrahydrocannabinol (delta9-THC), digitoxigenin and several biochemical compounds of research significance. LSD and delta9-THC in a mixture can be detected and identified by plasma chromatography positive mobility spectra in quantities of 10(-7) g or less. All the compounds investigated in this study display strong MH+ ions along with other ions primarily of the type (M)NO+, (M)2H+. None of these compounds exhibits negative mobility spectra.

Chromatography, Gel↗
PubMed1975

Detection of lysergic acid diethylamide, delta-9-tetrahydrocannabinol and related compounds by plasma chromatography.

Plasma chromatography as a method for ultratrace qualitative and quantitative detection of organic compounds is especially well suited for detection of gas chromatographic effluents. The optimum range of sample quantity is 10-6 to 10-12 g for detection and identification of a compound by use of its characteristic positive and negative mobility spectra. The type of reference mobility spectra produced by alkanes, aromatics, esters, halogenated compounds, nitrogenated compounds and organic acids have been previously reported. This study presents the reference mobility spectra produced for lysergic acid diethylamide (LSD), delta-9-tetrahydrocannabinol (delta-9-THC), digitoxigenin and several biochemical compounds of research significance. LSD and delat-9-THC in a mixture can be detected and identified by plasma chromatography positive mobility spectra in quantities of 10-7 g or less. All the compounds investigated in this study display strong MH-+ ions along with other ions primarily of the type (M)NO-+, (M)2H-+. None of these compounds exhibits negative mobility spectra.

Alanine↗
PubMed2001

The bactericidal effect and chemical reactions of acidified nitrite under conditions simulating the stomach.

AIMS: To examine the hypothesis of non-immune defence mechanisms based on nitrite. METHODS AND RESULTS: The acidified media (nutrient broth or citrate-phosphate buffer) under aerobic conditions with additions of physiological levels of nitrite, L-ascorbic acid, iodide and thiocyanate were used to simulate gastric juice. The bactericidal effects of acidified nitrite on Escherichia coli and lactobacilli were investigated using bacterial plate counts. Conversion of acidified nitrite to nitric oxide, nitrogen dioxide and nitrate was also studied. Nitrite significantly increased the bactericidal effects on E. coli and lactobacilli. The bactericidal effects were enhanced by thiocyanate but not by L-ascorbic acid and iodide. L-Ascorbic acid and thiocyanate, but not iodide, enhanced the decomposition of acidified nitrite in nutrient broth. Acidified nitrite was converted to both nitric oxide and nitrate, but a portion of the acidified nitrite in nutrient broth may have been converted to other unidentified nitrogen compounds. Nitrogen dioxide was not detected in any of the samples. CONCLUSION: The bactericidal effects of nitrite appeared to be primarily related to nitrous acid, and possibly to other unidentified nitrogenous metabolites, but not to nitric oxide and nitrogen dioxide. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential role of nitrite as an antimicrobial substance in the stomach may be of some importance in the ecology of the gastrointestinal tract and in host physiology.

Anti-Bacterial Agents↗
PubMed1983

Initial effects of the mount st. Helens eruption on nitrogen cycle and related chemical processes in ryan lake.

Ryan Lake, a 1.6-hectare basin lake near the periphery of the tree blowdown area in the blast zone 19 km north of Mount St. Helens, was studied from August to October 1980 to determine the microbial and chemical response of the lake to the eruption. Nutrient enrichment through the addition of fresh volcanic material and the organic debris from the surrounding conifer forest stimulated intense microbial activity. Concentrations of such nutrients as phosphorus, sulfur, manganese, iron, and dissolved organic carbon were markedly elevated. Nitrogen cycle activity was especially important to the lake ecosystem in regulating biogeochemical cycling owing to the limiting abundance of nitrogen compounds. Nitrogen fixation, both aerobic and anaerobic, was active from aerobic benthic and planktonic cyanobacteria with rates up to 210 nmol of N(2) cm h and 667 nmol of N(2) liter h, respectively, and from anaerobic bacteria with rates reaching 220 nmol of N(2) liter h. Nitrification was limited to the aerobic epilimnion and littoral zones where rates were 43 and 261 nmol of NO(2) liter day, respectively. Potential denitrification rates were as high as 30 mumol of N(2)O liter day in the anaerobic hypolimnion. Total bacterial numbers ranged from 1 x 10 to 3 x 10 ml with the number of viable sulfur-metal-oxidizing bacteria reaching 2 x 10 ml in the hypolimnion. A general scenario for the microbial cycling of nitrogen, carbon, sulfur, and metals is presented for volcanically impacted lakes. The important role of nitrogen as these lakes recover from the cataclysmic eruption and proceed back towards their prior status as oligotrophic alpine lakes is emphasized.

Journal Article↗
PubMed1991

[Nitrogen composition of the fruit juice of the Persian lime in Cuba].

In 1987 to 1989 the composition was studied of the nitrogen compounds (nitrogen and free amino acids) in the fruit juice of Persian lime during its commercial harvesting period. Adult Persian lime trees grafted on Citrus macrophylla and C. volkameriana were used, planted on a groundwater-affected red ferrilytic soil in the La Habana Province. Determination of the total nitrogen and of the free proline was carried out in May to July of each experimental year. The amino acid spectrum was established from juice samples in May 1987 and in July 1988. With the nitrogen concentrations varying between 14 and 90 mg/100 ml of juice, no consistent behaviour or pattern could be detected either in the total nitrogen content or the proline content in the juice during the 3 experimental years. 14 free amino acids were found, with about 90% of the total content formed from asparagine acid, glutamic acid, alanine, proline, gamma-aminobutyric acid, and arginine, regardless of the experimental year or the grafting basis.

Amino Acids↗
PubMed1978

Nitrogen-containing compounds in foundry mold emissions.

Nitrogen compounds have been identified in the decomposition products from several commonly used foundry sand binders. These compounds include nitrogen oxides, hydrogen cyanide, ammonia, simple aromatic amines, and isocyanates. The concentrations of these compounds in foundry mold emissions do not appear to be directly related to the nitrogen content of the organic binders. Measurable concentrations were observed in some cases, indicating the necessity for periodic, monitoring in the foundry. Adequate ventilation will permit the use of these binders. The substitution of nitrogen-free binders suggests another possible control strategy.

Air Pollutants↗
PubMedDate not supplied

Study of nitrogen containing compounds in the polar troposphere.

Atmospheric nitrogen compounds play a critical role in tropospheric photochemistry and are crucial to understand the chemical and physical evolution of atmospheric pollutants in polar areas. Measurements of these species in remote areas are rare, although their relevance is well established. Sampling campaigns of gaseous and particulate atmospheric trace species were performed in Arctic and in Antarctica during three consecutive years (1997-1999), using a proper combination of annular denuders and filter pack. After sampling, the ionic species were extracted with aqueous solutions and analysed by means of ion chromatography. Quality assurance on the sampling and analytical steps allowed accurate and precise measurements of all relevant compounds, which are thought to be important to nitrogen chemistry, at very low concentration levels. In addition, the measurements also included a multistage low-pressure impactor for the collection of particulate matter in different size regions (0.035-15.9 mm). Results obtained from these campaigns demonstrate that the minor components may be measured at levels as low as a few nanograms per cubic meter. The reported concentrations are to be considered among the first observations of nitrogen containing compounds in polar sites.

Air Pollutants↗
PubMedDate not supplied

Predictive carcinogenicity: a model for aromatic compounds, with nitrogen-containing substituents, based on molecular descriptors using an artificial neural network.

A back-propagation neural network to predict the carcinogenicity of aromatic nitrogen compounds was developed. The inputs were molecular descriptors of different types: electrostatic, topological, quantum-chemical, physicochemical, etc. For the output the index TD50 as introduced by Gold and colleagues was used, giving a continuous numerical parameter expressing carcinogenicity. From the tens of descriptors calculated, principal component analysis enabled us to restrict the number of parameters to be used for the artificial neural network (ANN). We used 104 molecules for the study. An Rcv2 = 0.69 was obtained. After removal of 12 outliers, a new ANN gave an Rcv2 of 0.82.

Carcinogenicity Tests↗
PubMed2004

[Characterization and quantitative determination of diesel fractions by comprehensive two-dimensional gas chromatography/time of flight mass spectrometry].

Comprehensive two-dimensional gas chromatography/time of flight mass spectrometry (GC x GC/TOFMS) has been applied for the analysis of diesel fractions. Two GC x GC methods are suggested. One is applied for exhaustive characterization and the other is used for the fast separation and quantitation of groups. No sample cleaning-up was required for both methods. Besides hydrocarbon compounds, the distributions of sulfur compounds and nitrogen compounds in a catalytic cracked diesel oil were investigated using the developed method. A total of 27 nitrogen compounds (including indole, alkyl indoles, carbazole and alkyl carbazoles) and 42 sulfur compounds (including benzothiophene, alkyl benzothiophenes, dibenzothiophene and alkyl dibenzothiophenes) were identified based on TOFMS and retention index. Quantitative determination of non-aromatics, mono-, di- and tri-aromatics of four diesel oils has been performed. The results are in good agreement with those from ASTM D2425 method.

Chromatography, Gas↗
PubMedDate not supplied

Involvement of nitrogen-containing compounds in beta-lactam biosynthesis and its control.

Biosynthesis of beta-lactam antibiotics by fungi and actinomycetes is markedly affected by compounds containing nitrogen. The different processes employed by the spectrum of microbes capable of making these valuable compounds are affected differently by particular compounds. Ammonium ions, except at very low concentrations, exert negative effects via nitrogen metabolite repression, sometimes involving the nitrogen regulatory gene nre. Certain amino acids are precursors or inducers, whereas others are involved in repression and, in certain cases, as inhibitors of biosynthetic enzymes and of enzymes supplying precursors. The most important amino acids from the viewpoint of regulation are lysine, methionine, glutamate and valine. Surprisingly, diamines such as diaminopropane, putrescine and cadaverine induce cephamycin production by actinomycetes. In addition to penicillins and cephalosporins made by fungi and cephamycins made by actinomycetes, other beta-lactams are made by actinomycetes and unicellular bacteria. These include clavams (e.g., clavulanic acid), carbapenems (e.g., thienamycin), nocardicins and monobactams. Here also, amino acids are precursors and inhibitors, but only little is known about regulation. In the case of the simplest carbapenem made by unicellular bacteria, i.e., 1-carba-2-em-3-carboxylic acid, quorum sensors containing homoserine lactone are inducers.

Amino Acids↗
PubMed1976

[Research on nitrogen heterocyclic compounds. X. New method of synthesis of pyrrolo/1,2-a/quinoline and its derivatives].

The synthesis of pyrrolo[1,2-a]quinoline derivatives from 1-arylpyrroles bearing an acetic acid or acetonitrile moiety on the benzene or pyrrole nucleus is described. Pyrrolo [1,2-a]quinoline derivatives have some pharmaceutical interest as cyclic analogues of 9H-pyrrolo[1,2-a]indole and 5H-pyrrolo[2,1-c] [1,4]-benzodiazepine, the basic structures of the antitumor antibiotics mitomycin C, anthramycin and tomaymycin.

Antineoplastic Agents↗
PubMed1995

Utilization of dietary protein in the vitamin B12-deficient rats.

Utilization of dietary protein in vitamin B12 (B12)-deficient rats was evaluated by determinating the content of plasma protein, urinary excretion of nitrogen compounds, and nitrogen-balance after the rats were fed on a B12-deficient soy bean protein diet by pair-feeding for 100 days. The severe B12-deficiency was confirmed in rats by a remarkable increase in urinary methylmalonic acid excretion and a remarkable decrease in the hepatic B12 level. Growth of B12-deficient rats was significantly retarded as compared both with ad libitum-feeding control rats and pair-feeding control rats. The growth retardation due to B12-deficiency was alleviated by the administration of 1 microgram/day of CN-B12 for 30 days. Plasma total protein and albumin levels in rats fed on a B12-deficient diet decreased, compared with those in pair-feeding control, and increase in urea-nitrogen was observed. The excretion of urinary nitrogen compounds, such as urea-nitrogen, allantoin, and creatinine, was significantly depressed by B12-deficiency compared with those in pair-feeding control. The administration of CN-B12 to B12-deficient rats for 30 days resulted in the recovery of the changes in plasma proteins and urinary excretion of nitrogen compounds. The above results suggested that the extreme B12-deficiency depressed the utilization of dietary protein in rats. Moreover, the decrease in urinary urea-nitrogen excretion was supposed to be due to the adaptation by the depression of the dietary protein utilization.

Animal Nutritional Physiological Phenomena↗
PubMed2002

A novel superfamily of transporters for allantoin and other oxo derivatives of nitrogen heterocyclic compounds in Arabidopsis.

A wide spectrum of soil heterocyclic nitrogen compounds are potential nutrients for plants. Here, it is shown that Arabidopsis plants are able to use allantoin as sole nitrogen source. By functional complementation of a yeast mutant defective in allantoin uptake, an Arabidopsis transporter, AtUPS1 (Arabidopsis thaliana ureide permease 1), was identified. AtUPS1 belongs to a novel superfamily of plant membrane proteins with five open reading frames in Arabidopsis (identity, 64 to 82%). UPS proteins have 10 putative transmembrane domains with a large cytosolic central domain containing a "Walker A" motif. Transport of (14)C-labeled allantoin by AtUPS1 in yeast exhibited saturation kinetics (K(m) approximately 52 microM), was dependent on Glc and a proton gradient, and was stimulated by acidic pH. AtUPS1 transports uric acid and xanthine, besides allantoin, but not adenine. Protons are cosubstrates in allantoin transport by AtUPS1, as demonstrated by expression in Xenopus laevis oocytes. In plants, AtUPS1 gene expression was dependent on the nitrogen source. Therefore, AtUPS1 presumably is involved in the uptake of allantoin and other purine degradation products when primary sources are limiting.

Allantoin↗
PubMed2003

Atmospheric nitrogen compounds-issues related to agricultural systems.

Workable pollution abatement policies and effective legislation must be based on sound science. However, despite many years of research, there are still uncertainties about the effects of atmospheric nitrogen compounds on crops and other vegetation. This paper reviews the current state of knowledge of the main compounds, focussing on the concentrations and combinations of pollutants that occur in rural areas. The sources, concentrations and effects of oxidised, reduced and organic nitrogen compounds are considered in turn, then the effects of deposited nitrogen on ecosystems are discussed. Research priorities on the effects of deposited nitrogen in Europe and the USA are compared. Finally, the review leads to a list of issues for discussion and recommendations for research.

Agriculture↗
PubMed1995

[Effect of nitrogen-containing compounds on the biosynthesis of avermectins].

The influence of complex nitrogen-containing substrates (Difko yeast extract, EKD nutrient yeast extract, soy bean flour and cotton seed meal), ammonium salts and some amino acids (alanine, methionine, valine, isoleucine and threonine) on the biosynthesis of avermectins in the cultures of two mutants of Streptomyces avermitilis was studied. It was shown that an excess of the nitrogen compounds in the fermentation medium induced a decrease in the antibiotic biosynthesis and the relative content of the group B avermectins.

Amino Acids↗
PubMedDate not supplied

[Biotransformation of nitrogen-containing compounds in the process of the continuous final purification of effluents from swine-breeding farms by immobilized cells].

After their two-step purification in aeration tanks, effluents from a swine-breeding farm were subjected to final purification in a flow bioreactor with immobilized cells derived from activated sludge. The dynamics of nitrogen compounds were studied at the reactor inlet and outlet at three flow rates. The use of a simple mathematical model of the nitrogen balance allowed the rates of nitrogen assimilation-mineralization two nitrification stages, and nitrogen fixation-denitrification to be estimated. The first stage of nitrification was found to proceed intensely and produce high nitrite concentrations (up to 100 mg N/l, accounting for about half of the total N at the inlet). The second nitrification stage was inhibited, and nitrate was only produced after 3-4 weeks of continuous operation. The strategy of the final purification of effluents from nitrogen compounds is discussed on the basis of the known regulatory mechanisms of microbial activities in activated sludge.

Animal Husbandry↗