Cover picture: Proton channels formed by the transmembrane domain of M2 protein from influenza A virus, showing the column of waters which fills the lumen. This snapshot is taken after 1 ns of molecular dynamics simulation in an explicit lipid bilayer (not shown for clarity). Helices are colored from red to yellow with increasing root mean squared fluctation of atoms over the simulation. The ring of His³⁷ residues, essential for low-pH activation of the channel, are shown in blue spacefill and occlude the pore. See the article by Forrest et al. on p. 55.