  It has been known that the uptake mechanisms of cell-penetrating
peptides(CPPs) depend on the experimental conditions such as concentration of
peptides, lipid composition, temperature, etc. In this study we investigate the
temperature dependence of the penetration of Arg9s into a DOPC/DOPG(4:1)
membrane using molecular dynamics(MD) simulations at two different
temperatures, T = 310 K and T = 288 K. Although it is difficult to identify the
temperature dependence because of having only one single simulation at each
temperature and no evidence of translocation of Arg9s across the membrane at
both temperatures, our simulations suggest that followings are strongly
correlated with the penetration of Arg9s: a number of water molecules
coordinated by Arg9s, electrostatic energy between Arg9s and the lipids
molecules. We also present how Arg9s change a bending rigidity of the membrane
and how a collective behavior between Arg9s enhances the penetration and the
membrane bending. Our analyses can be applicable to any cell-penetrating
peptides(CPPs) to investigate their interactions with various membranes using
MD simulations.
