Table 3.

Estimation of the binding and gating interaction

Site	Ωbinding	ΔGbinding (kcal mol−1)	Ωgating	ΔGgating (kcal mol−1)
δW57	1.3	0.2	1.0	0
δD59	0.5	−0.4	0.3	−0.7
ɛG57	2.0	0.4	1.3	0.1

The coupling coefficient (Ω) and interaction free energy changes (ΔG) between the tailgroup of ACh and the δ57, δ59 and ɛ57 sites. The Ω and ΔG were calculated separately for the agonist binding process and the channel gating. Ω was calculated as (K_{wild type- Ach} X K_mutant-TMA)/ (K_mutant-ACH X K_{wild-type-TMA}) where k refers to the binding equilibrium constant K_D (k-/k₊) or the gating equilibrium constant Θ(β/α). ΔG was calculated as 0.59 In (Ω).