Fig. 1.

Mechanism of membrane permeation depends on peptide sequence. (A and B) R₆ (unlabeled) added to 20/60/20 PS/PE/PC GUVs (red) with encapsulated Alexa Fluor 633 dye (blue) induced permeation fast enough to rupture vesicles. (C and D) Addition of a single tryptophan hydrophobic residue drastically changed the dominant mode of translocation/escape: R₆W (unlabeled) induced slow leakage of intact vesicles, similar to antimicrobial peptides. (E and F) Labeling R₆ with the hydrophobic aromatic rings of fluorescein isothiocyanate (FITC, green) also gave rise to slow leakage of encapsulated dye, followed by eventual equilibrium distribution of the R₆-FITC peptide (G). White scale bars are 20 μm.