Cells and bodily fluids possess strong nanosecond-lifetime autofluorescence, therefore photoluminescent probes with microsecond-scale luminescence decay time would be useful for analysis of biological samples, as they allow the performance of measurements in time-resolved (TR) format in a time gate (time window) where the nonspecific background fluorescence has ceased. We have previously disclosed binding-responsive luminescent probes for protein kinases (PKs), ARC-Lum(Fluo) probes. High brightness of the probes is achieved through intramolecular Forster-type resonant energy transfer (FRET) from excited triplet state of a thiophene- or selenophene-comprising phosphor (3D*) to singlet acceptor dye (1A) leading to amplified emission from the dye. Here, we determined quantum yields (QYs) and oxygen sensitivity of separate phosphorescent donor and fluorescent acceptor and compared these with those of the corresponding ARC-Lum(Fluo) probes both in nonbound and PK-bound states. The microsecond-scale luminescenc...