Table 1.

Residual Currents and Calculated Difference Potentials at the Selectivity Filter for Substitutions at Residue-13 of μCTX

Substitution	Δϕ (kT/e, at Cβ of A1529) relative to WT toxin	Fres (0 mV)
R13K	−0.1	0.05
R13Q	−1.0	0.30
R13E	−1.8	0.48