The hydrophobic core of biological membranes presents a physical barrier to polar and charged molecules.  These membranes also play host to a wide variety of proteins that are vital to cellular functions.  For one such family of proteins, voltage gated potassium ion channels, it has been speculated that the movement of charged arginine residues across the membrane is required for proper gating function. Using molecular dynamics simulations, we study the energetics of an arginine analog, methyl guanidinium, as it traverses a lipid bilayer.  We find the potential of mean force (PMF) for permeation to be approximately 29 kcal/mol, much higher than is biologically feasible.  Further simulations investigate the influence of salt concentration and of water penetration on the PMF.  By restricting the entry of water into the bilayer center, we quantify the stability added by water within the bilayer center.

Methyl guanidinium permeation through a lipid bilayer using molecular dynamics simulations with polarizable charge equilibration force fields

243rd National Meeting (2012)

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