Phase information, assumed known from three‐beam diffraction experiments, has been used successfully as input to direct methods to re‐determine the crystal structure of rubredoxin. With data at 1.54 Å resolution, starting sets containing 26 single phases, or alternatively 45 triplet phases, in both cases known with a mean error of ±22.5°, were sufficient to initiate solution of the structure. Conventional figures of merit were employed in the early stages to reject the majority of the incorrect phase models. The presence of a FeS4cluster in the structure was used in the interpretation of the initial maps. Phase sets including 2500E's with a mean single phase error 〈Δϕ〉≃ 70° or a mean triplet phase error 〈ΔΦ3〉≃ 80°, both relative to the model from the crystallographic refinement, could be refined and expanded by Fourier recycling using theSAYTANformalism. Several parameters have been varied to study their influence on phas
展开▼
