PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Nitrogen Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1980

Structure-toxicity relationships of selected nitrogenous heterocyclic compounds.

A series of eleven nitrogen-containing heterocyclic compounds, which may be potentially associated with aqueous effluents from coal conversion technologies, were examined to determine the relationships between their n-octanol/H2O partition coefficients, molecular weights, boiling points, and their toxicity monitored as reproduction impairment to Tetrahymena pyriformis. Toxicity increases linearly with increased partition coefficient, molecular weight, and boiling point. All of these parameters increase with increased alkyl and ring addition.

Animals↗
PubMed2004

Systemic analysis of structures and contents of nitrogen-containing compounds and other non-hydrocarbons in crude oils in conjunction with chemometric resolution technique.

A method is described for the systemic identification and quantitative analysis of nitrogen-containing compounds and other non-hydrocarbons in crude oils. The pre-fractionation of a crude oil sample into 7 fractions was performed by di-adsorption column chromatography using neutral aluminum oxide and silica gel. A subsequent high-resolution separation of individual components was achieved by using capillary column gas chromatography, and compound types were detected by a mass spectrometer. In conjunction with a chemometric method, the compounds in the fractions were further resolved or separated, which made it possible to identify some nitrogen-containing compounds and other non-hydrocarbons in crude oils. To a certain extent, this method could relieve the difficulty of classical analysis in identifying those species with very low contents or incompletely separation, particularly in the cases where authentic standards were not available for addition into the unknown samples in order to reveal what indeed existed in them. The structures and contents of 168 nitrogen-containing compounds in one crude sample and 60 non-nitrogen-containing compounds in one of non-hydrocarbon fractions of this oil sample were determined, and the addition-recovery examination of some standard compounds showed that the analytical veracity was satisfactory.

Journal Article↗
PubMed2003

Research and control of well water pollution in high esophageal cancer areas.

AIM: In order to detect risk factors for esophageal cancer, a national research program was carried out during the Eighth Five-Year Plan (from 1991 to 1995). METHODS: Cixian County and Chichen County in Hebei Province were selected as the index and the control for the study fields with higher or lower incidence of esophagus cancer in China, respectively. In these areas, we investigated the pollution of three nitrogenous compounds in well water for drinking and the use of nitrogen fertilizer in farming. RESULTS: In well water, nitrate nitrogen, nitrite nitrogen and ammonia nitrogen were 8.77 mg/L, 0.014 mg/L and 0.009 mg/L in Cixian County in 1993, respectively. They were significantly higher than their levels (3.84 mg/L, 0.004 mg/L and 0.004 mg/L) in Chichen County (P<0.01, t=6.281, t=3.784, t=3.775). There was a trend that the nitrogenous compounds in well water increased from 1993 to 1996. The amount of nitrogen fertilizer used in farming was 787.6 kg per hectare land in Cixian County in 1991, significantly higher than 186 kg per hectare in Chichen County (t=9.603, P<0.001). CONCLUSION: These investigations indicate that the pollution of nitrogenous compounds in well water for drinking is closely related to the use of nitrogen fertilizer in farming, and there is a significantly positive correlation between the level of three nitrogenous compounds in well water and the mortality of esophageal cancer (correlation coefficient =0.5992). We suggest that improvement of well system for drinking water quality should be an effective measure for esophageal cancer prevention and control in rural areas.

China↗
PubMed1997

Prediction of pKa values of phenolic and nitrogen-containing compounds by computational chemical analysis compared to those measured by liquid chromatography.

The pKa values of 64 phenolic and 50 nitrogen-containing compounds were obtained by reversed-phase liquid chromatography and computational chemical calculation. The chromatographically obtained values of phenolic compounds were equal to pKa values from references and Hammett's equation, and those of nitrogen-containing compounds were lower than the reference values. It appeared difficult to calculate the properties of the ortho effect and nitro group by the computational calculation method. However, the calculation was simpler than selecting different constants of Hammett's equation for a variety of compounds.

Computer Simulation↗
PubMed2006

[Development of efficient methods for synthesis of nitrogen-containing compounds using carbamates, acylhydrazines, and ammonia].

For the efficient synthesis of divergent nitrogen-containing compounds of pharmaceutical and agricultural importance, the development of efficient, complementary, and new synthetic methodologies is essential. One of the key subjects is how to introduce nitrogen atoms in to organic molecules. This review summaries our recent efforts on this issue, focusing on the use of carbamates, acylhydrazines, and ammonia as nitrogen sources.

Ammonia↗
PubMed2005

Effect of nitrogen-containing compounds on polychlorinated dibenzo-p-dioxin/dibenzofuran formation through de novo synthesis.

An experimental study was conducted to clarify the suppression effect of nitrogen-containing compounds, that is, ammonia and urea, on the formation of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) through the de novo synthesis reaction. In the experiment, graphite and copper chloride contained in a mixture were used as sources of carbon and chlorine, respectively. The granulated sample mixture was charged as a packed-bed in the glass tube and heated at 300 degrees C in the flow of Ar-O2 gas mixture. In some cases, urea was added as aqueous solution to the sample, while ammonia was added to the gas flowed through the sample bed. The amount of PCDD/Fs formed decreases significantly by the addition of both ammonia and urea. Particularly, the addition of urea reduces the amount of PCDD/Fs discharged in the outlet gas by approximately 90%. The oxidation rate of carbon in the early stage of the experiment, that is, the heating period, is promoted bythe addition of nitrogen-containing compounds. However, soon afterthe temperature reaches 300 degrees C, the formation rate becomes lower than that of the case without the addition of nitrogen-containing compounds. On the other hand, organic compounds containing amino (-NH2) or cyanide (-CN) groups and those containing nitrogen within the carbon ring frame were detected in the outlet gas in the case of urea addition. Typically observed aromatic compounds are chlorobenzonitriles, chlorobenzeneamines, and chloropyridines. This suggests a possibility that hydrogen and/or chlorine combined with PCDD/Fs are also substituted by such nitrogen-containing groups, and this decreases the formation rate of their frame of carbon rings. This phenomenon was also consistent with the fact that a significant reduction was observed in the amount of PCDD/Fs released to the outlet gas when urea was added.

Benzofurans↗
PubMed1982

[Use of proteins in the feed mixture in early weaning of pigs].

Eighty-three piglets weaned at the average age of 28, 27 and 25 days were subjected to three trials to compare the effectiveness of the use of complete feed mixtures for early-weaned piglets (COS 1 and COS 2) and experimentally prepared mixtures lower in protein and higher in energy, in some cases with an addition of carbadox. In the first 14 days after weaning the piglets fed the mixtures with 90 to 95 g less nitrogen compounds in kg had the same body weight gains, higher feed consumption, and 20% lower consumption of nitrogen compounds per kg of gain than had the piglets given the COS 1 mixture. In the subsequent period of six to thirteen days, the production data demonstrated the economic effectiveness of the use of the experimentally prepared mixtures (the condition was that the level of nitrogen compounds did not decrease to 152 g per kg). The improvement of protein conversion through an increase in the ratio of digestible energy to feed protein by 50%, as compared with the COS 1 mixture at the nitrogen-compound content of 200 g per kg, and the possibility of further reduction in nitrogen compound level after 14 days from weaning, indicate the way how to change the system of nutrition in early-weaned piglets. The high-protein commercial mixture, used to-date, causing high uraemia in the piglets, is not suitable, as demonstrated by physiological, health, and particularly economic data.

Animal Feed↗
PubMed1987

Computer-assisted structure-activity relationships of nitrogenous cyclic compounds tested in salmonella assays for mutagenicity.

Study of the relationship between mutagenicity and molecular structure for a data set of nitrogenous cyclic compounds is reported. A computerized SAR system (ADAPT) was utilized to classify a data set of 114 nitrogenous cyclic compounds with 19 molecular descriptors. All of the descriptors represented at least 10% of the compounds in the data sets. The average correct predictability of the data base was calculated to be 89% after evaluating 100 training/prediction subsets. The actual predictive ability of the discriminants generated by the ADAPT system was demonstrated by predicting the mutagenicity of structurally similar compounds not in the data set. Weight vectors generated in the pattern recognition programs were used to predict the bacterial mutagenicity of 10 compounds which were not included in the data set. All of the compounds were predicted correctly which was actually better than the 89% calculated by the system. This displayed the ability of the system of classify compounds as mutagenic or nonmutagenic by using molecular descriptors and to predict the biological activity of untested chemicals with a high degree of confidence. This paper presents the uses of this type of SAR approach in a research laboratory.

Heterocyclic Compounds↗
PubMed2000

Automated solid-phase synthesis of linear nitrogen-linked compounds.

A synthetic library motif has been developed to create linear, nitrogen-linked compounds as screening libraries to target structured RNA for drug discovery. Scaffolds were created in situ from suitably protected bifunctional compounds linked together either by acyl or amine links. Acyl links were created from amino acids, which also introduce one degree of functionality. Amine links from the amino acid nitrogen were created from an N-protected amino alcohol via Fukuyama Mitsunobu alkylation. Each amine site can then be used for introducing functionality or extending the scaffold. This synthetic scheme can be used to create a wide variety of modified-backbone PNA in situ, as shown by the synthesis of a PNA-type monomer. The synthesis steps have been enabled on a 96-well parallel-array synthesizer for high-throughput synthesis. The present study represents a versatile synthetic approach to a wide variety of potential RNA-binding molecules.

Amides↗
PubMed1984

Cellular membrane contrast and contrast differentiation with osmium triazole and tetrazole complexes.

Addition of heterocyclic nitrogen compounds to the classical osmium tetroxide postfixation medium, applied after glutaraldehyde fixation, results in enhanced membrane contrast in ultrathin sections of liver tissue. The addition of similar compounds to potassium osmate solutions, results in contrast differences in some cellular membranes. The membranes of the rough endoplasmic reticulum, the nuclear envelope and the plasma membrane acquire contrast, while the mitochondrial membranes do not. The apolar regions of membranes are contrasted when osmium tetroxide is combined with heterocyclic nitrogen compounds, whereas the polar regions are contrasted by combinations of potassium osmate with these compounds. This polar membrane contrast is probably due to the presence of an amino-group in the heterocyclic nitrogen compounds. Compounds without the amino-group do not contrast membranes, although the glycogen is contrasted. X-ray microanalysis served to establish the relative osmium content in contrasted glycogen, and showed that such nitrogen compounds play a role in complexation of cations in aldehyde-fixed tissues. Electron spectroscopy for chemical analysis (ESCA) measurements of isolated muscle glycogen show that after treatment with various osmium tetroxide or potassium osmate solutions, hexavalent and quadrivalent osmium species are present in the glycogen. The presence of (heterocyclic) nitrogen compounds in such solutions stabilizes certain osmium valency species, and this may account for the contrast observed.

Amitrole↗
PubMed1988

The evolution of nitrogen cycling.

Based upon arguments concerning properties of the environment and the energetics of nitrogen transformation reactions, new hypotheses regarding their evolution are presented. These hypotheses are supported by new calculations and observations germane to understanding the evolution of the nitrogen cycle. From calculations of shock production by meteor impact, we suggest that impact produced fixed nitrogen could have resulted in the entire reservoir of Earth's N2 being converted into fixed nitrogen at the end of accretion. We have significantly improved upon previous calculations of the abiotic fixation rate on the early earth and find a rate of fixation by lightning of approximately 1-3 x 10(16) molecules NO/J, which is 2 to 3 times greater than previous estimates. This strengthens the suggestion, corroborated by the predominance of a single nitrogenase enzyme, that biological nitrogen fixation may have been a late evolutionary development, after the development of an aerobic atmosphere. In addition, we show for the first time that HNO, predicted to be the main product of atmospheric photochemical reactions involving NO on the primitive Earth by photochemical models, would eventually become NO2- and NO3- after reaching the Earth's surface. Based upon microbe-environment interactions on an ecological as well as a biochemical scale we suggest that denitrification arose prior to aerobic respiration and that nitrification arose after the advent of an aerobic atmosphere. We hypothesize the following evolutionary sequence for the biological transformation of nitrogen compounds: Ammonification --> Denitrification --> Nitrification --> Nitrogen fixation.

Ammonia↗