Table 3.

Atom types used to classify atoms forming protein-ligand binding sites.

Atom Type	Definition
Hydrophobic	Aliphatic or aromatic C
Aromatic	Aromatic C
Hydrogen bond donor	Hydrogen bonded to N, O, or S
Hydrogen bond acceptor	N, O, and S with lone electron pairs
Positive	Ionizable Gasteiger positive charge
Negative	Ionizable Gasteiger negative charge
Metallic	Mg, Zn, Mn, Ca, or Fe
Excluded Volume	All atom-types