Map-likelihood phasing

Terwilliger, T.C.

doi:10.1107/S0907444901013749

Figure 5
Effect of solvent content on map-likelihood phasing with no prior phase information. The mean true figure of merit (〈cosΔφ〉) is plotted as a function of cycle number for simulations with solvent contents of 53, 59, 66 and 73%. Simulations were started with zero phase information (a flat map). Starting probability distributions for electron density in the protein and solvent regions were taken from the first cycle of the simulation shown in Fig. 2

(a) (for the simulation with 73% solvent). For all subsequent cycles, probability distributions were estimated by cross-validation as follows. The general procedure was to obtain an `omit' map in which each point was derived from a density-modification cycle in which that point had not been included in the solvent mask. An `omit' region was uniformly defined as `protein', regardless of its actual location. Three cycles of density modification were carried out and the `omit' region was saved. Omit regions covering the entire asymmetric unit were calculated and combined to make a complete `omit' map of the asymmetric unit. This map was used to estimate probability distributions for density in the protein and solvent region for the next overall cycle.

BIOLOGICAL
CRYSTALLOGRAPHY

ISSN: 1399-0047

Volume 57| Part 12| November 2001| Pages 1763-1775

doi:10.1107/S0907444901013749

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