Development of luminescent terbium(III) chelates for protein labelling: Effect of triplet-state energy level

The synthesis of novel Tb-III labels suitable for protein labelling are reported. Their luminescence properties as antibody conjugates were measured and compared to the results of corresponding Tb-III chelates of the parent ligand structures. When the lowest triplet-state energy level of the parent donor ligand was over 23 000 cm(-1), i. e., the energy gap between the D-5(4) level of Tb-III and the lowest triplet-state energy level of the ligand exceeded 2600 cm(-1), the label derivative with a long decay time (tau=1.35-2.93 ms) and a high luminescence yield (epsilon.Phi=3770-4560) was found to be suitable for bioaffinity assays.