Fig. 7.

Schematic depiction of processes involving helical peptide partitioning between water (w), bilayer (bi), and translocon (tl). The horizontal double arrows denote an equilibrium between translocon and bilayer, with a free energy change ΔG _app. This is the process assumed to be probed by the translocon-mediated insertion experiments. The vertical double arrows denote an equilibrium between bilayer and water, with a free energy change ΔG _wbi. This is the process considered in simulation studies of Arg (and analogs) insertion in membranes. The diagonal double arrows denote a hypothetical process involving equilibrium partitioning of the peptide between the translocon and water, with a free energy change ΔG _wtl. The entry of the peptide into the translocon and subsequent secretion (denoted by vertical arrows labeled “enter” and “exit”) are likely nonequilibrium processes