Figure 2.

Model building of β-sheets in density-modified experimental electron-density maps. (a, b) Sections of the electron-density map and model from S-­hydrolase (Turner et al., 1998 ▶) in which the β-sheet model is largely correct (a) and incorrect (b). The refined model C^α trace is shown in light brown and the β-sheet C^α trace is shown in dark brown. (c) Ribbon diagram of part of the model obtained from structure 1038B at a resolution of 3 Å showing β-­sheets (PDB entry 1lql; Choi et al., 2003 ▶). (a) and (b) were created with Coot (Emsley & Cowtan, 2004 ▶) and (c) was created with PyMOL (DeLano, 2002 ▶).