Eur. Phys. J. Special Topics 222, 2595-2605 (2013)
https://doi.org/10.1140/epjst/e2013-02040-9

Regular Article

Dynamics of ions in the selectivity filter of the KcsA channel Towards a coupled Brownian particle description

¹ Centre for Scientific Computing, University of Warwick, Coventry, CV4 7AL, UK
² School of Engineering, University of Warwick, Coventry, CV4 7AL, UK
³ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
⁴ Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK
⁵ Mission Critical Technologies Inc., 2041 Rosecrans Ave. Suite 225 El Segundo, CA 90245, USA
⁶ Physics Department, Lancaster University, LA1 4YB Lancaster, UK

^a e-mail: s.cossedu@warwick.ac.uk

Received: 16 July 2013
Revised: 13 August 2013
Published online: 28 October 2013

Abstract

The statistical and dynamical properties of ions in the selectivity filter of the KcsA ion channel are considered on the basis of molecular dynamics (MD) simulations of the KcsA protein embedded in a lipid membrane surrounded by an ionic solution. A new approach to the derivation of a Brownian dynamics (BD) model of ion permeation through the filter is discussed, based on unbiased MD simulations. It is shown that depending on additional assumptions, ion's dynamics can be described either by under-damped Langevin equation with constant damping and white noise or by Langevin equation with a fractional memory kernel. A comparison of the potential of the mean force derived from unbiased MD simulations with the potential produced by the umbrella sampling method demonstrates significant differences in these potentials. The origin of these differences is an open question that requires further clarifications.