The impact of cell-penetrating peptides on membrane bilayer structure during binding and insertion

•The effect of penetratin on bilayer structure was studied using DPI.•Penetratin bound weakly to neutral bilayers and strongly to anionic bilayers.•The binding of penetratin to gel-phase DMPC/DMPG followed a two-state model.•The binding of short-form penetratin to POPC/POPG followed a two-state model.•New insight into the membrane-penetrating property of penetratin