Table 9.

Energy scores for the complexes formed by the tested compounds 3a–e and the reference colchicine in the active site of β-tubulin enzyme (PDB: 3HKC).

Compound	S Score	ΔG (kcal/mol)a	Ligand–Receptor Interaction
			Residue	Type	Length (Å)
Colchicine	−5.62	−3.4 −0.5	Glu 71 Mg 601	H–donor metal	3.16 2.61
3a	−7.05	−2.2 −0.6	Mg 601 Ala 247	metal pi–H	2.00 4.17
3b	−7.16	−0.9 −2.3 −0.9	Asp 245 Arg 2 Glu 71	H–donor H–acceptor pi–H	3.27 3.41 3.98
3c	−6.29	−1.8 −0.7 −0.7	Mg 601 Tyr 224 Ala 247	metal pi–H pi–H	2.40 3.79 4.50
3d	−6.94	−1.0 −2.1 −0.7	Glu 71 Mg 601 Arg 2	H–donor metal pi–H	3.90 2.51 4.69
3e	−6.43	−2.0 −2.2	Gln 11 Mg 601	H–acceptor metal	3.09 2.33

ΔG (kcal/mol)^a: the binding free energies.