Table 1.

The calculated and measured affinities of the studied compounds (see Figure 1) to L. stagnalis acetylcholine-binding protein (AChBP). A—HEPES-bound; B—DHβE-bound and C—α-cobratoxin-bound forms of AChBP respectively; *—only a part of the compound could be docked correctly because of multiple rotatable bonds; **—the binding outside “classical” agonist/competitive antagonist site is predicted; n.d.—not determined (no positive solutions). The measured affinities were obtained as follows: firstly, the respective IC₅₀ values were calculated from inhibition curves (see Figure 2) using ORIGIN 7.5 and then converted into the K_is according to Cheng-Prusoff equation (see Experimental Section) with the mean ± s.e.m. values of duplicate or triplicate measurements for each compound concentration.

Compounds	Theoretical calculated Ki values (μM) for interaction with L. stagnalis AChBP			Experimental Ki values (μM) at interaction with L. stagnalis AChBP from radioligand assay
	A	B	C
1 *	n.d.	n.d.	39	28 ± 4
2 *	n.d.	n.d.	39	130 ± 10
3	0.98	1.7 0.64 **	2.0	0.83 ± 0.04
4	1.6	0.97	0.75	0.79 ± 0.03
5	2.2	0.46	5.8	1.3 ± 0.1
6	0.05	0.04	0.97	0.55 ± 0.01
7	8.2	0.79 0.50 **	1.7	>1000
8	33	12	310	540 ± 60
9	0.08	0.47	0.40	27 ± 2
10	170	120	n.d. 320 **	>1000
11	150	83 11 **	350	>1000
12	1.5	5.3	19	3.0 ± 0.4
13 *	0.53	0.43	0.11	2.5 ± 0.4