Table 2. Twenty amino acids were classified according to five physicochemical properties.

Physicochemical property	Amino acid
Aliphatic group (G1)	G, A, V, L, M, I
Aromatic group (G2)	F, Y, W
Positive charge group (G3)	K, R, H
Negative charge group (G4)	D, E
Uncharged group (G5)	S, T, C, P, N, Q