FIGURE 7.

(A) Gibbs energy of binding to the membrane interface determined experimentally ( $\mathrm{\Delta }{G}_{\mathit{bind}}^o$) as a function of the mean characteristic time τ for CF release from POPC LUV. Each point corresponds to a peptide: TP10W and its mutants TPW-1, TPW-2, and TPW-3; TP10, the C-terminal carboxylate versions TP10-COO⁻ and TP10W-COO⁻, and the fluorophore-modified TP10-7MC (8, 15). The solid symbols correspond to entirely experimental data, both for binding and dye release. The open symbols correspond to TP10 and TP10-COO⁻, for which τ is experimental but the binding affinity is calculated with the Wimley-White scale (neither contains Trp). The line is a fit with a slope of 1. (B) Gibbs energy of transfer to octanol calculated with the Wimley-White scale ( $\mathrm{\Delta }{G}_{\mathit{oct}}^o$) as a function of the mean characteristic time τ for CF release from POPC LUV. The points correspond to the same peptides as in (A). The open symbol corresponds to TP10-7MC for which $\mathrm{\Delta }{G}_{\mathit{oct}}^o$ is an estimate assuming a replacement of the modified Lys by Tyr, which gave good agreement with $\mathrm{\Delta }{G}_{\mathit{bind}}^o$ when used to calculate $\mathrm{\Delta }{G}_{if}^o$ for binding using the Wimley-White interfacial scale. The line is a fit with a slope of 1 (excluding the TP10-7MC point).