| 초록 |
Ion channels are membrane proteins that allow rapid movement of ions across membranes. Gramicidin A (gA) channel, the simplest one, is formed by head-to-head association of two monomers at their amino termini. The gA channel is selective for monovalent cations, with no measurable permeability to anions or polyvalent cations. In this work, we have investigated the conduction of a single ion through the gA channel by using MD simulations. To simulate complete, continuous conduction events of a single ion through the channel within a feasible computing time, we employ the technique of steered MD (SMD) that accelerates the conduction by applying external forces on a single ion. Employing Jarzynski's equality between free energy and irreversible work, we can obtain the free energy profile along the conduction pathway. The calculated profile pinpoints barriers and binding sites inside the channel. We examine valence selectivity of the gA channel by performing SMD of K+, Ca2+ and Cl-. |
