Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphate may be determined in serum without deproteinization as the phosphomolybdic acid complex by UV-spectrophotometry. The rate of complex formation is dependent on the acidity and the concentration of molybdate. The photometric measurements should be performed at a longer wavelength than in maximum absorptivity of the phosphomolybdic acid complex to permit practical high concentrations of molybdate in the reagents. Citric acid will hinder the complex formation, but will not interfere with the stability of the phosphomolydbic acid. The phosphomolybdic complex is determined by adding citric acid to the samples before (blank) and after (test) the molybdate. The analytical procedure has been automated on a Greiner GSA II, Greiner Electronics, Switzerland.
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PMID:Determination of serum-phosphate without deproteinization by ultraviolet spectrophotometry of the phosphomolybdic acid complex. 744 50

Two-electron oxidation of 2,2,5,7,8-pentamethyl-6-chromanol (PH), a model compound of alpha-tocopherol, gives the unstable 8a-hydroxy-2,2,5,7,8-pentamethyl-6-chromanone (POH) which rearranges to form stable 2-(3-hydroxy-3-methylbutyl)-3,5,6-trimethyl-1,4-benzoquinone (PQ). POH and PQ are isomers which have the same oxidation state. The aim of this work was to compare the ease of reduction of POH and PQ at room temperature using a variety of biological and chemical reductants in a reductant:POH (PQ) ratio of 20:1 (or 16:1). Ascorbic acid completely reduced POH to PH in 20 min, but had no effect on PQ after 40 min. Sodium ascorbate did not reduce POH or PQ at all after 40 min. Sodium dithionite reduced POH to PH (85%) in 20 min, but reduced PQ to its hydroquinone, PQH2 (67%) in 40 min. Dithiothreitol produced a slight reduction of POH to PH (21%) but reduced PQ to PQH2 (69%). NADH/FAD reduced POH and PQ to PQH2 (73% and 42%, respectively) in 10 min. It was concluded that POH is easier to reduce than PQ and more likely to form PH as a product, particularly under conditions of mild acidity.
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PMID:Reduction of 8a-hydroxy-2,2,5,7,8-pentamethyl-6-chromanone. 1268 4