Analysis of ion current blockades at cis/−100 mV or trans/+100 mV side addition of chitohexaose on the single channel insertion of WT and its mutant. Shown is a plot of residence (dwell) time (τc) (A and C) and open time (τo) (B and D) versus various concentrations of chitohexaose. ●, WT; ○, W136A; ■, W136F; ♀, W136R; , W136D. Error bars, S.D.