TABLE 1

Comparison of the affinity constants of the aziridinium ions of AChM and BR384 determined from the kinetics of receptor alkylation with those estimated for ACh and McN-A-343 in competition experiments with [³H]NMS

Receptors	[³H]NMS Competition^{^a} −Log K_i			Kinetics of Alkylation^{^b} Log K_i
Receptors	NMS	ACh	McN-A-343	AChM	BR384
M1 receptor
Wild type	9.36 ± 0.02	3.88 ± 0.03	4.83 ± 0.03	3.61 ± 0.05	5.13 ± 0.08
D105N	7.81 ± 0.05	2.20 ± 0.04	3.82 ± 0.01		3.44 ± 0.46
M2 receptor
Wild type	9.11 ± 0.01	5.68 ± 0.04	4.59 ± 0.04	4.41 ± 0.05	4.88 ± 0.08
D103N	7.93 ± 0.07	3.01 ± 0.06	4.20 ± 0.05		3.58 ± 0.13

↵a The parameter values ± S.E.M. were estimated from the [³H]NMS competition curves shown in Fig. 7.
↵b The parameter values ± S.E.M. were estimated by global nonlinear regression analysis of the data in Figs. 5 and 6 using eqs. 1 (AChM) and 4 (BR384).