Fig. 6. The effect of sugar on collisional quenching of Trp-151 fluorescence. Stern–Volmer plots of Trp-151 fluorescence quenching by Cs (Cesium) (A), I
(Iodide) (B), or acrylamide (C) in the absence (filled circles) or presence (open circles) of 15mMTDG are shown. Purified detergent-solubilized single-W151C154G
LacY (5 M) was titrated with small aliquots of stock solutions of 5 M CsCl, KI, or acrylamide. The data were fit to linear Stern–Volmer plots (see Experimental
Procedures), and KSV values were calculated from the slope of the plots. Fluorescence spectra were recorded as described previously.