Figure 13.

Fluorescence change induced by Na⁺ binding to wild-type and the Phe mutants of all nine Trp residues of human thrombin. Shown are the values of the total change in intrinsic fluorescence (black bars), or the amplitude of the fast phase (grey bars). All values are expressed as % change relative to the baseline. Experimental conditions are: 50 nM thrombin, 5 mM Tris, 0.1% PEG, pH 8.0 at 15 °C.