A specific region (or atom) in a
molecular entity that is capable of entering into a stabilizing interaction with another molecular entity. An example of such an interaction is that of an active site in an enzyme with its
substrate. Typical forms of interaction are by
hydrogen bonding,
coordination and
ion pair formation. Two binding sites in different molecular entities are said to be complementary if their interaction is stabilizing.
Source:
PAC, 1994, 66, 1077
(Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994))
on page 1089