Table 2. Quenching of HPO fluorescent iron chelators by various metal ions in a cell-free system.
The fluorescence of CP603, CP623, CP645, CP655 (5 μM each) and CP800 (0.5 μM) in Tris buffer (50 mM, pH 7.5, 20 °C) was recorded at their respective excitation and emission maxima by using a PerkinElmer spectrofluorimeter. The metal ions were added as their corresponding salts (see the Materials and methods section) at a final concentration of 10 μM. The decrease in fluorescence is expressed as a percentage of the initial fluorescence intensity (set at 0% quenching) with the buffer as blank without probe (set at 100%). Spectra were not corrected for light intensity, detector sensitivity and photobleaching of the probes.
| Fluorescence (%) | |||||
|---|---|---|---|---|---|
| CP655 | CP645 | CP623 | CP603 | CP800 | |
| Fe3+ | 92 | 93 | 97 | 96 | 66 |
| Fe2+* | 92 | 94 | 97 | 97 | 63 |
| Zn2+ | 15 | 11 | 17 | 14 | 9 |
| Ni2+ | 7 | 11 | 7 | 10 | 6 |
| Cu+* | 10 | 11 | 8 | 6 | 9 |
| Cu2+ | 42 | 50 | 49 | 40 | 31 |
| Co2+ | 11 | 12 | 15 | 11 | 8 |
| Ca2+ | 3 | 8 | 5 | 8 | 4 |
* Measurements were performed in the presence of the reducing equivalent ascorbic acid (200 μM).