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. 2007 Feb 16;92(10):3556–3563. doi: 10.1529/biophysj.106.102210

FIGURE 4.

FIGURE 4

Quenching of Trp fluorescence in MscL by di(Br2C18:0)PC. Efficiencies of fluorescence quenching are plotted for Trp residues in M1 (○) and M2 (□) as a function of the distance (Å) of the α-carbon of the residue from that of Leu-69, measured along the bilayer normal. Efficiencies of quenching were calculated as 1-F/F0, where F and F0 are fluorescence intensities in di(Br2C18:0)PC and di(C18:1)PC, respectively. Residues in the center of the membrane that will be quenched by brominated lipid molecules in both halves of the bilayer have not been included. Data points labeled 1, 2, 3, and 4 correspond to I23W, A20W, I77W, and L73W, respectively. Experimental values of fluorescence intensity are averages of duplicate measurements from three separate reconstitutions. The data for residues in M2 are from Powl et al. (15).