Table 1. Features related to side-chain variations.

Residue types	Arg, Glu, Gln, Lys and Met	Phe, Trp and Tyr
Degree of freedom	High	Low
Accessibility	Exposed	Buried
Hydrophobicity	Hydrophilic	Hydrophobic
Shape	Linear	Planar
Aromatic	No	Yes
Electron density	Less clear	Clearer