FFig. 14. Structure formability of hypothetical proteins composed of 4 amino acids. The numbers represent the degree of structure formability of the hypothetical proteins, when one of four [GADV]-amino acids is replaced with another amino acid. Minus symbols mean that the 4 amino acids did not satisfy the 4 structural conditions. At the left column, amino acids are placed in order number of atoms on a side chain of an amino acid, or in order structure simplicity of the amino acid.