| amino_acids | The 20 standard amino acids | 
| amino_acids_properties | Amino acid side chain property values | 
| amino_acid_pairs | Generate amino acid pairs | 
| as_one_letter | Convert three-letter amino acid codes to one-letter codes | 
| as_three_letter | Convert one-letter amino acid codes to three-letter codes | 
| grantham_distance | Grantham distance | 
| grantham_distances_matrix | Grantham distance matrix | 
| grantham_equation | Grantham distance |