Figure 1.

Averages over the last 2 ns of three 6 ns simulations with light backbone constraints, here using the CHARMM27 force field. Each M2 channel’s (a) average protein-backbone RMSD of residues 26–43 from model 1 of its PDB structure, (b) average water content between residues 27–41, and (c) initial/final trajectory frames are shown. The end-view snapshots of the initial (blue) and final (red) structures below demonstrate the relative stability of the tilted helix bundle. Side views better show the variations between PDB models,⁵⁶ but the end-view was chosen here to demonstrate the volume of the central cavities.