W0158

Phase Constrained Solvent Flattening. Ronald Shigeta, Kurt Thorn, Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215 USA

Single isomorphous replacement (SIR) phasing results in a bimodal phase distribution, with two phases being equally probable. Real space solvent flattening, where the constraint of a uniform solvent density is imposed, has been very useful in removing this ambiguity and creating interpretable electron density maps. However, conventional solvent flattening ignores the information present in the SIR phase distribution.

We have developed a procedure by which the solvent flattened phase is constrained to one of the two peaks in the SIR phase distribution. An optimal choice between these two phase choices results in a map correlation of 0.62 to the final refined model as compared to 0.51 for the initial SIR map.

Different protocols for flattening the electron density and choosing the final phase are being investigated and results will be presented.