FIGURE 2.

Fluorescent properties of cryptate of terbium, Lumi4-Tb. (A) Structure of the terbium cryptate (lumi4-Tb). (B) Temporal selectivity. The introduction of a time delay (usually about 50 μs) between a flash excitation (blue flag) and the measurement of the fluorescence (orange zone) at the acceptor emission wavelength allows to discriminate long lived from short-lived fluorescence and to increase signal-to-noise ratio. (C) Spectral compatibility. Absorption (dark blue line) and fluorescence emission (light blue line) of Lumi4-Tb. The lanthanide cryptate exhibits four emission peaks: 490, 548, 587, and 621 nm. Lumi4-Tb as donor is therefore compatible with fluorescein-like (green zone) and Cy5- or dy647-like (red zone) acceptor to perform TR-FRET experiments.