AbstractArginine (R)-rich peptides constitute the most relevant class of cell-penetrating peptides and other membrane-active peptides that can translocate across the cell membrane or generate defects in lipid bilayers such as water-filled pores. The mode of action of R-rich peptides remains a topic of controversy, mainly because a quantitative and energetic understanding of arginine effects on membrane stability is lacking. Here, we explore the ability of several oligo-arginines R$$_n$$
n
and of an arginine side chain mimic R$$_\mathrm {Side}$$
Side
to induce pore formation in lipid bilayers employing MD simulations, free-energy calculations, breakthrough force spectroscopy and leakage assays. Our experiments reveal that R$$_\mathrm {Side}$$
Side
but not R$$_n$$
n
reduces the line tension of a membrane with anionic lipids. While R$$_n$$
n
peptides form a layer on top of a partly negatively charged lipid bilayer, R$$_\mathrm {Side}$$
Side
leads to its disintegration. Complementary, our simulations show R$$_\mathrm {Side}$$
Side
causes membrane thinning and area per lipid increase beside lowering the pore nucleation free energy. Model polyarginine R$$_8$$
8
similarly promoted pore formation in simulations, but without overall bilayer destabilization. We conclude that while the guanidine moiety is intrinsically membrane-disruptive, poly-arginines favor pore formation in negatively charged membranes via a different mechanism. Pore formation by R-rich peptides seems to be counteracted by lipids with PC headgroups. We found that long R$$_n$$
n
and R$$_\mathrm {Side}$$
Side
but not short R$$_n$$
n
reduce the free energy of nucleating a pore. In short R$$_n$$
n
, the substantial effect of the charged termini prevent their membrane activity, rationalizing why only longer $$\mathrm {R}_{n}$$
R
n
are membrane-active.
"UNRAVELING KEY INTERACTIONS THAT LEADS THE STABILITY OF NBD-14010 BINDING TO GP120 OF HIV-1: AN MD SIMULATIONS AND FREE ENERGY PERSPECTIVES"