On the application of phase relationships to complex structures. XXXII. A small protein at low resolution.

The direct-methods program SAYTAN is applied to data at various restricted resolutions for a small protein. It is shown that useful sets of phases can be obtained even down to 3 A resolution. Conventional figures of merit are not very discriminating for the phase sets developed, but modified figures of merit seem capable of selecting the better phase sets, at least for those generated from 2 A or higher resolution data.