Figure 1. Sketch of the backbone structure of the protein methionine aminopeptidase from Escherichia coli. The chain begins at the amino-terminus (N), includes 264 amino acids, and ends at the carboxy-terminus (C). The protein includes helices and sheet strands as well as two metal ions (spheres) at the active site. Reprinted from Bazan JF et al. (1994) Proceedings of the National Academy of Sciences of the USA 91: 2473–2477, figure 2.

Figure 2. Relationship between the hydrophobicities of the amino acids and the solvent-accessible areas of their side-chains. Reprinted and adopted from Chothia C (1974) Nature 248: 338–339, figure 1.

Figure 3. Loss of protein stability, G, for a series of leucine-to-alanine substitutions within T4 lysozyme. ‘L99A’, for example, denotes the mutant in which leucine 99 is replaced by alanine. Mutations that result in cavities of the largest volume cause the greatest loss of stability. At a cavity volume of zero, the loss of stability can be attributed to the difference between the hydrophobicity of leucine and alanine. Reprinted and adapted from Xu J et al. (1998) Protein Science 7: 158–177, figure 17A.