Cover picture: A view down the channel of the MscS protein showing the seven equivalent subunits and the leucine side chains (yellow) that form the narrowest part of the pore. Although the channel appears open, in the absence of an applied field the leucines form a hydrophobic gate that precludes conduction through the channel. However, applying a strong transmembrane potential enables ion flow. See the article by Spronk et al. on page 3555.