Figure 23.4.4.9 

Distribution of solvent-binding sites in 18 mutant T4 lysozymes from ten refined crystal structures. The lysozyme structures were compared to identify common sites of hydration. A total of 1675 solvent molecules were included in the comparison. Each solvent molecule is represented by a coloured sphere. The size of the sphere is proportional to the number of lysozyme structures in which solvent was observed at the same site (i.e. within 1.2 Å). In addition, the colour of the solvent changes from blue for the least-conserved sites to red for the most-conserved ones [e.g. the red spheres indicate that solvent is observed with high frequency (15–17 times) at the four internal sites]. The numbers indicate representative residue positions along the backbone of the lysozyme molecule. Reprinted with the permission of Cambridge University Press from Zhang & Matthews (1994). Copyright (1994) The Protein Society.