Figure 5.

Fluorescence titration of RNase(K41R) with PPL-L-alanine. Fluorescence was measured with 5 μM RNase(K41R) in 50 mM 4-methylmorpholine pH 7.5 at 25°C. PPL-L-alanine concentrations were 10, 12, 15, 20, 25, 40 and 50 μM. A, Fluorescence spectra; B, nonlinear regression analysis gives a K'_d value of 23 μM. Bovine RNase A contains six tyrosine residues and no tryptophan residue [45].