Holographic methods in X-ray crystallography. Pt. 4. A fast algorithm and its application to macromolecular crystallography

The holographic method makes use of partially modeled electron density and experimentally measured structure-factor amplitudes to recover electron density corresponding to the unmodeled part of a crystal structure. This paper describes a fast algorithm that makes it possible to apply the holographic method to sizable crystallographic problems. The algorithm uses positivity constraints on the electron density and can incorporate a 'target' electron density, making it similar to solvent flattening. The potential for applying the holographic method to macromolecular X-ray crystallography is assessed using both synthetic and experimental data. (orig.)