Nonamer channel
Next we developed atomic scale models of the nonamer channel using S/N = 4/3 for the second β-barrel as occurs in the Lysenin structure. Upon examining these models, however, we observed a substantial amount of empty space between the two barrels. Reducing S/N of the middle barrel to 2/3 (the next value permissible for 9-fold symmetry with a three-stranded subunit) reduces the diameter of this barrel by ~1.2 nm, leaving a gap distance between the walls of the two barrels of only 0.6 nm, the lowest gap distance we allow.