HOW DOES SOLVENT FLATTENING REMOVE THE PHASE AMBIGUITY. Bi-Cheng Wang, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, U.S.A. and Department of Crystallography, University of Pittsburgh, Pittsburgh, PA 15260, U.S.A.

Although solvent flattening is now widely used for improving electron density maps, the theoretical basis of how this approach can remove the phase ambiguity has not been fully discussed. This presentation will address the basic phasing power of solvent flattening. It will show how this approach can, in principle, systematically remove the phase ambiguity by removing the noise associated with it. The lecture will also address the precautions in the use of single isomorphous replacement and single-wavelength anomalous scattering data as well as data accuracy which is essential to this technique. Calculated and experimental data will be used in the illustration. An extension of solvent flattening techniques to multi-wavelength anomalous scattering data will also be presented.