Fluorescence labelling with europium chelate of beta-diketones and application in time-resolved fluoroimmunoassays (TR-FIA).

Five beta-diketone derivatives were studied for multiple labelling of proteins. The labelled proteins were characterized by absorption and fluorescence measurements. It was found that proteins labelled with chlorosulfonyl-thenoyltrifluoroacetone (CTTA) were able to form highly fluorescent complexes with Eu3+ which exhibited prolonged fluorescence whereas the Eu3+ complex of hydrolyzed CTTA exhibited almost no fluorescence, and so unreacted ligand gave no background signal in immunoassays even if it was not removed from the labelled reagent. The effect of labelling on the biological activity of albumin and polyclonal antibody was studied and it was also shown that the new probe could be used in time-resolved fluorescence immunoassays.