Five principal component scores for the 20 amino acids (obtained based on PCA using 12 physico-chemical properties; Opiyo and Moriyama, submitted) AA PC1 PC2 PC3 PC4 PC5 Ala -1.74 -2.24 -1.88 0.41 -0.06 Arg 0.68 3.56 0.79 2.28 1.08 Asp -2.24 0.84 0.23 -1.99 0.51 Asn -1.82 0.98 0.53 -0.53 0.27 Cys -0.22 0.30 -0.72 -0.67 -0.81 Glu -0.61 1.55 -1.14 -2.07 0.77 Gln -0.69 1.65 -0.75 -0.55 0.65 Gly -4.02 -2.56 1.12 0.58 -0.42 His 0.04 2.36 -1.18 -0.05 -1.67 Ile 2.16 -2.24 0.02 0.51 0.34 Leu 1.93 -1.85 -1.21 0.26 -0.60 Lys -1.31 2.26 -0.91 2.51 -0.41 Met 1.83 0.07 -1.76 -0.37 0.00 Phe 3.56 -0.97 0.28 -0.23 0.00 Pro -2.07 -0.11 2.45 -0.22 -1.39 Ser -2.63 -1.01 0.47 0.13 0.24 Thr -1.36 -0.44 0.62 0.03 0.91 Trp 4.96 0.41 1.22 -0.46 -0.56 Tyr 2.59 0.50 2.12 -0.46 0.29 Val 0.98 -3.05 -0.28 0.91 0.87