  Ion channels are important proteins for physiological information transfer
and functional control. To predict the microscopic origins of their
voltage-conductance characteristics, we here applied dissipation-corrected
targeted MD in combination with LE simulations to potassium diffusion through
the Gramicidin A channel as a test system. Performing a non-equilibrium
principal component analysis on backbone dihedral angles, we find coupled
protein-ion dynamics to occur during ion transfer. The dissipation-corrected
free energy profiles correspond well to predictions from other biased
simulation methods. Employing Langevin simulations taking into account an
external electric field predicts macroscopic observables in the form of I-V
characteristics, which exhibit good agreement with their experimental
counterparts, but highlight the necessity to include polarization effects in
ion diffusion simulations.
