title: The influence of assay conditions on measurement of excitatory dibasic sulphinic and sulphonic alpha-amino acids in nervous tissue.
abstract: Major improvements to the HPLC separation of fluorescent derivatives of excitatory sulphur-containing amino acids have been made. Quisqualate was used as the internal standard since no endogenous derivatives coeluted with it. The artefactual generation of sulphinic and sulphonic amino acids from the oxidation of cysteine (56 microM) and homocysteine (1.2 microM) has been investigated using deionised water, an acidic phosphate/methanol mixture, perchloric acid and trichloroacetic acid (TCA) as extraction media. Of the four extraction media examined, TCA in combination with ether extraction was shown to be the most potent oxidative treatment and resulted in 23% oxidation of original cysteine or homocysteine to sulphinic and sulphonic acids. This oxidation was partially resistant to the presence of physiological concentrations of glutathione (1.5 mM) such that in the case of cysteine, 6% oxidation was observed. A 10% (v/v) mixture of methanol in 75 mM phosphate solution (pH 4.6) was found to be the most artefact-free extraction method and in spinal cord tissue processed with this medium, cysteine sulphinic acid was the only excitatory sulphur-containing amino acid consistently detectable (0.24 +/- 0.01 pmol/mg wet weight, n = 6).
authors.affiliation: Department of Pharmacology, School of Medicale Sciences, University Walk, Bristol, U.K.
authors.forename: S J
authors.initials: SJ
authors.lastname: Waller
authors.forename: I C
authors.initials: IC
authors.lastname: Kilpatrick
authors.forename: M W
authors.initials: MW
authors.lastname: Chan
authors.forename: R H
authors.initials: RH
authors.lastname: Evans
mesh_terms: D000603:Amino Acids, Sulfur / Q000032:analysis*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003545:Cysteine / Q000031:analogs & derivatives / Q000032:analysis; D005612:Freeze Drying; D006710:Homocysteine / Q000031:analogs & derivatives / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D008297:Male; D009417:Nerve Tissue / Q000737:chemistry*; D018377:Neurotransmitter Agents; D010084:Oxidation-Reduction; D010472:Perchlorates; D051381:Rats; D011919:Rats, Inbred Strains; D012015:Reference Standards; D012997:Solvents; D014238:Trichloroacetic Acid
chemical_list: D000603:Amino Acids, Sulfur; D018377:Neurotransmitter Agents; D010472:Perchlorates; D012997:Solvents; D006710:Homocysteine; C007956:homocysteic acid; D014238:Trichloroacetic Acid; D003545:Cysteine; C013461:cysteine sulfinic acid