Is single-wavelength anomalous scattering sufficient for solving phases? A comparison of different methods for a 2.1 Å structure solution

Abstract

The structure of rusticyanin is the largest unknown structure (M(r) = 16.8 kDa) which has been recently solved by the direct-methods approach using only single-wavelength anomalous scattering (SAS) data from the native protein [Harvey et. al. (1998). Acta Cryst. D54, 629-635]. Here, the results of the Sim distribution approach [Hendrikson and Teeter (1981). Nature (London), 290, 107-113] and of the CCP4 procedure MLPHARE [Collaborative Computational Project, Number 4 (1994). Acta Cryst. D50, 760-763] are compared with those from direct methods. Analysis against the final refined model shows that direct methods produced significantly better electron-density maps than the Sim distribution and MLPHARE approaches (average phase error was around 63°in both cases).