Table 3. Distances between Heteroatoms of the Vinca Site of Tubulin and Those of VLB, Metabolites 8, 10, and 11 Involved in Hydrogen Bonds.

		distance among hydrogen bond donor (HBD) and hydrogen bond acceptor (HBA) atoms (Å)
subunit	H-bonds interactions	VLB	MTB8	MTB10	MTB11
CT	N16′ + Lys176	2.3	2.2	2.4	2.3
	OH + Val177	1.9	2.0	2.0	1.7
VD	ester C4 + Asn329	2.1	2.0	2.1	1.9
	ester C3 + Lys336	2.3	2.4	2.6	2.5
ΔGbinding (kJ/mol)		–11.23	–12.18	–13.39	–14.24