Summary
It has been found that cysteine inhibits the oxidation of sulphanilic acid by potassium persulphate, catalysed by silver(I). This is due to blocking of the catalyst through the formation of catalytically non-acitive complexes of the catalyst with the inhibitor. When cysteine and the activator 2,2′-bipyridyl are present at the same time in the system, concurrent complex formation proceeds, which improves the sensitivity and selectivity of the reaction. On this basis, a convenient colorimetric catalytic method for the determination of cysteine in the 5.0×10−7–4.0×10−6 M range, in the presence of the 20 protein-forming amino-acids is proposed.
Zusammenfassung
Cystein behindert die durch Ag(I) katalysierte Oxydation von Sulfanil-säure durch Kaliumpersulfat. Dabei wird der Katalysator durch Bildung inaktiver Komplexe mit dem Inhibitor blockiert. Wenn Cystein und der Aktivator 2,2′-Bipyridyl gleichzeitig im System zugegen sind, läuft eine konkurrierende Komplexbildung ab, die die Empfindlichkeit und Selektivität der Reaktion verbessert. Auf dieser Grundlage wurde eine Bestimmungsmethode für Cystein in 5,0×10−7 bis 4,0×10−6-molarer Konzentration in Gegenwart der 20 eiweißbildenden Aminosäuren ausgearbeitet.
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Alexiev, A.A., Angelova, M.G. A novel catalytic colorimetric method for the determination of nanomolar cysteine concentrations in amino-acid mixtures. Mikrochim Acta 80, 369–379 (1983). https://doi.org/10.1007/BF01202014
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DOI: https://doi.org/10.1007/BF01202014