Figure 3.

Iodide quenching of the tryptophan fluorescence in the PerCter–Ca²⁺/CaM complex. A solution of 10 μM PerCter alone (□) or in the presence of 20 μM CaM (■) was titrated with 100 mM KI. Emission spectra were recorded at least 10 min after addition to ensure equilibrium conditions. Spectra were corrected for background and dilution before being integrated from 310–450 nm. Fractional fluorescence (F_o/F) was then determined by dividing the area under the unquenched spectrum by the respective quenched spectrum.