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At least 937 records · Page 52Linked to original sources
PubMed2005

Chelates of cobalt(III) and iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol as test probes for the characterization of chromatographic effects on a reversed-phase liquid chromatography stationary phase.

The chromatographic effects on a reversed-phase liquid chromatography (RPLC) phase were established with the use of chelates system: cobalt(III) and iron(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol as the test probes. Both chelates have the same octahedral structure, M:L = 1:2, the former chelate is cationic and can be used to probe the ion-exchange phenomena on a RPLC phase, whereas the latter is not charged and can be used as reference molecule with respect to the charged one. Based on well-established LC phenomena referred in the literature, the suitability of the chelate system for examining some chromatographic effects was tested. It was concluded that the proposed test method is sensitive towards the ion-exchange phenomena on the LC phase and the hydrogen bonding between the solvent eluent and the LC phase. In addition, chromatographic effects due to the presence of ultrasonic field or due to the presence of aromatic amines in the eluent were observed with the help of the proposed test method. Based on molecular computation, the properties of chelates were compared with properties of quaternary amines, the probes most frequently used for testing LC phases, and the possible differences in an interaction of the mentioned compounds with a surface of a RPLC phase were indicated.

Azo Compounds↗
PubMed2003

Reaction cascades initiated by nucleophilic attack of heteropentalene mesomeric betaine and nitrogen-rich mesoionic tetrazolium-5-amides on electron-deficient unsaturated compounds. Synthesis of novel heterocyclic systems.

The reactions of heteropentalene mesomeric betaine 1 and nitrogen-rich mesoionic tetrazolium-5-amides 4, 11 and 16-18 with electron-deficient unsaturated compounds have been studied. Novel heterocyclic systems, tetrazolo[4,5-a][1,7]benzodiazonine inner salt 2 and 3-oxo-3,7-dihydro-2H-pyrazolo[3,4-b]pyridine 5, have been synthesized by the reactions of dimethyl acetylenedicarboxylate with 1 and tetrazolium-5-anilide 4, respectively, and fully characterized by X-ray crystallography. It has been found that the reactions of other tetrazolium-5-amides are also initiated by the nucleophilic addition of the electron-rich amide nitrogen to the electron-deficient unsaturated compounds.

Amides↗
PubMed1985

The effect of diet on the mammalian gut flora and its metabolic activities.

The review will encompass the following points: A brief introduction to the role of the gut flora in the toxicology of ingested food components, contaminants, and additives, including known pathways of activation and detoxication of foreign compounds and the implication of the flora in enterohepatic circulation of xenobiotics. The advantages and disadvantages of the various methods of studying the gut flora (classical bacteriological techniques, metabolic and enzymological methods) will be critically discussed with special reference to their relevance to dietary, toxicological, and biochemical studies. Sources of nutrients available to the gut flora will be described including host products (mucus, sloughed mucosal cells, hormones, proteins) and exogenous nutrients derived from diet. An account of the problems involved in studies of dietary modification with special reference to the use of stock laboratory animal diets, purified diets, and human dietary studies. The influence of dietary modification on the flora will be assessed on the basis of changes in numbers and types of bacteria and their metabolic activity, drawing on data from human and animal studies. The effects of manipulation of the quantity and quality of protein, fat, and indigestible residues (fiber) of the diet will be described together with their possible implications for toxicity of ingested compounds.

Amino Acids↗