Figure 2.
Peptide binding by tryptophan fluorescence titration. This figure shows the results of binding experiments performed with the peptides MelP5_Δ4 and MelP5_Δ6. Panels a and b show tryptophan emission spectra after titration of 10 µM peptide with increasing amounts of POPC vesicles at pH 4. Panel c shows the lipid dependence of the change in fluorescence intensity (I/Io) at 335 nm, at pH 4, after correction for light scattering effects (see text). Data such as those in panel c were fit to Equation 1 to obtain mole fraction partitioning coefficients for each peptide/pH combination. Panel d shows the change in free energy of partitioning with respect to pH.