Figure 1.
The fluorescent probe L can form a complex ML with the metal ion M yielding a second fluorescent species with reduced radiative rate (kem,ML).
Figure 2.
Fluorescence and UV/VIS studies on the quenching of TMR-bipy-DNA by CuSO4.
(A) Stern-Volmer plot of TMR-bipy-DNA fluorescence quenching by CuSO4 (closed circles) shows a pronounced negative deviation from the Stern-Volmer law for collisional quenching (solid line) that can be explained using the model from eq. (1) for fitting the data (dashed line). (B) Absorption of TMR-bipy-DNA shows only a very weak dependency on the addition of CuSO4.
Figure 3.
Single-molecule studies on the quenching of TMR-bipy-DNA by CuSO4.
(A) Confocal fluorescence image of single ATTO620-bipy-DNA molecules immobilized on glass cover slides via biotin/streptavidin. Image (30×15 µm2) taken using pulsed excitation with a diode laser emitting at 635 nm with a repetition rate of 80 MHz at an average excitation power of 5.5 µW in presence of 0.1 µM CuSO4. Time-resolved traces of single immobilized dye-bipy-DNA molecules labeled with TMR (B), ATTO 620 (C) and ATTO 633 (D) recorded under the same conditions show discrete dark states due to reversible complexation of Cu2+ and bipyridine which leads to intramolecular quenching of the fluorescence emission.
Table 1.
Model parameters estimated by using eq. (1) to fit data for fluorescence quenching of different dye-bipy-DNA by Cu2+.
Figure 4.
Energy optimized snapshots from different MD trajectories of Cu2+/TMR-bipy-DNA at large separation (A) and two different TMR/bipy orientations constrained at short separations (B, C).
Table 2.
Model parameters estimated by using eq. (1) to fit data for fluorescence quenching of TMR-bipy-DNA by different metal cations M2+ compare with data for respective 4,4′-dicarboxybipyridine complexes from literature and calculated Förster radii for energy transfer between TMR and the M2+-bipy complex.