FIGURE 4.
Fluorescence properties of purified Clomeleon in solution under varying chloride and pH conditions. (a) R-values of purified Clomeleon at different chloride concentrations. R-values reduced exponentially on increasing the chloride concentrations. (b) The contributions of lifetimes τ1 (solid), τ2 (shading), and τ3 (light shading) at the donor emission maximum were calculated from the pre-exponential factors and plotted as normalized fractional contributions with increasing chloride concentrations. The contributions of τ1 and τ3 were most affected in contrast to τ2. (c) The mean lifetimes of Clomeleon at the donor emission maximum increased exponentially with increasing chloride concentrations, yielding the Stern-Volmer plot. (d) R-values of purified Clomeleon at different pH levels. R-values reduced drastically at acidic pH levels. (e) The fractional contributions of the lifetimes τ1 (solid), τ2 (shading), and τ3 (light shading) at the donor emission maxima were plotted as a function of pH. The contributions of τ1 and τ3 were most affected in contrast to τ2. (f) The donor mean lifetimes of Clomeleon showed a Gaussian fit with high quenching effects at acidic pH levels and high FRET at pH >7.3.