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Time-resolved europium fluorescence in enzyme activity measurements: a sensitive protease assay

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Original languageEnglish
Pages (from-to)399-403
Number of pages5
JournalJournal of applied biochemistry
Issue number6
Publication statusPublished - Dec 1983
Externally publishedYes
Publication typeA1 Journal article-refereed


A method for incorporating into proteins a nonradioactive Eu3+ label, which exhibits fluorescence of a long decay time in the presence of suitable ligands, is described. As an example of the use of this label the method has been developed to work as a sensitive protease assay. By hydrolyzing the Eu3+-labeled casein, bound to an insoluble matrix (Sepharose 4B or Affi-Gel 10), with proteases and measuring the Eu3+ released with a pulsed time-resolved fluorometer it was possible to detect as low as 2.5, 1.0, or 1.0 ng of alpha-chymotrypsin, trypsin, or subtilisin, respectively.


  • Animals, Bacillus, Cattle, Chymotrypsin, Europium, Kinetics, Microchemistry, Pancreas, Spectrometry, Fluorescence, Subtilisins, Swine, Trypsin

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