a) Crystal structure of HEWL automatically built by ARP/wARP after phasing using the sulfur signal. The anomalous map is shown in orange countered at 4σ whereas the 2F_obs − F_calc electron density map is shown in blue contoured at 1.5σ. (b) Electron density map (2F_obs − F_calc) calculated from SAD experimental phases of a Leptospira interrogans putative lipoprotein crystal contoured at 1.2σ (cyan). The quality of the map allowed automatic building of most of the polypeptide chain (gray). The figure was prepared using PYMOL (DeLano, 2002).