Figure 3
From: A novel approach for protein subcellular location prediction using amino acid exposure
Principal component analysis of the vectors of exposure of the 20 amino acids shown in Figure 2. Amino acids with similar properties appear close in the projection: polar residues like arginine (R), aspartic acid (D), glutamic acid (E) and lysine (K) group together. Same is true for alcoholic (threonine (T), serine (S)) and aromatic (tryptophan (W), histidine (H), tyrosine (Y), phenylalanine (F)) residues.