ABSTRACT
The potential of (33)S NMR spectroscopy for biochemical investigations on taurine (2-aminoethanesulfonic acid) is explored. It is demonstrated that (33)S NMR spectroscopy allows the selective and unequivocal identification of taurine in biological samples. (33)S NMR spectra of homogenated and intact tissues are reported for the first time, together with the spectrum of a living mollusc. Emphasis is placed on the importance of choosing appropriate signal processing methods to improve the quality of the (33)S NMR spectra of biological tissues.
Subject(s)
Magnetic Resonance Spectroscopy/methods , Taurine/analysis , Animals , Cattle , Mollusca , Sheep , Sulfur IsotopesABSTRACT
A simple alternative colorimetric method has been developed for quantitative determination of phenylpyruvic acid in urine based on the improved stability of the ferric complex of enol-phenylpyruvate in water-dimethylsulfoxide 50% vol. mixed solvent. The method can be applied directly to urine or to a dry ether-extract of urine. Operating on the dry ether-extract of urine, detection of phenylpyruvic acid is possible at an amount of as low as 1 mg/100 ml. Whereas, if urine samples are processed, detection is possible for a concentration of as low as 5 mg/100 ml and quantitative determination for a concentration greater than 10 mg/100 ml. The test carried out on a diaper wet with urine retains the same sensitivity and shows instantaneous development of the green colour.
Subject(s)
Phenylpyruvic Acids/urine , Chlorides , Colorimetry/methods , Dimethyl Sulfoxide , Ferric Compounds , Humans , Indicators and ReagentsABSTRACT
The tautomerism of phenylpyruvic acid (PPA) and its sodium salt was investigated. The 1H and 13C spectra of PPA in aprotic solvents and in methanol show almost complete prevalence of the enol form, whereas the keto form prevails only in water. The Z configuration was assigned to the sole enol tautomer present on the basis of the value of the vicinal coupling constant [3J1H, 13COOH]=3.7 Hz. A small amount of the hydrated form of PPA (1-phenyl-2, 2-dihydroxylpropanoic acid) was found in the aqueous solution of its sodium salt and in buffer solution (pD=6) of PPA. By means of infrared spectroscopy one can conclude that crystalline PPA is in the enol whereas its sodium salt is in the keto form. The keto-acid was not obtained in the solid state. The colorimetric method for testing PPA traces in urine depends on the formation of a enol-Fe3+ complex (2:1) which appears stable in dimethylsulfoxide (DMSO).
