Skip to main content
. Author manuscript; available in PMC: 2011 Jun 21.
Published in final edited form as: Biochemistry. 2006 Nov 7;45(44):13249–13263. doi: 10.1021/bi0611964

Figure 4.

Figure 4

Fluorescence emission quenching by iodide and changes in average emission wavelength, 〈λ〉, vs pH. The Stern–Volmer quenching constants, KSV, are a measure of the accessibility of the active site tryptophan residues to iodide. (A and B) KSV values were determined for the quenching of tryptophan fluorescence emission over the pH range of 3–9 for (A) procaspase-3(D3A) (○) and (B) mature caspase-3 (○) and the (pro)caspase-3 mutants (●). The solid lines represent fits of the data as described in Experimental Procedures. For panels C and D, the average emission wavelength, 〈λ〉, was determined over the pH range of 2.4–9 for procaspase-3(D3A) (○), mature caspase-3 (○), and each (pro)caspase-3 mutant (□). The solid lines represent fits of the data as described in Experimental Procedures. For panels A–D, representative data are shown for E167A, and results for all mutants are provided as Supporting Information.