Properties of an electron-density map derived from a limited number of experimentally determined triplet phases.
In a previous communication [Weckert et al. (1999). Acta Cryst. D55, 1320-1328], the feasibility of the measurement of a large set of triplet phases by three-beam interference was demonstrated. This paper reports the methodology for the calculation of an electron-density map from this limited amount of experimental phase information and the map's properties with respect to model building and refinement. The tetragonal form of hen egg-white lysozyme (HEWL) was chosen as a test structure for the development of this method. The quality of the electron-density map obtained from all measured triplet phases allows a straightforward and nearly complete interpretation. The starting model was refined to a final R value of 17.4%. In a second step, the minimum number of phased reflections needed for the interpretation of an electron-density map was investigated, applying criteria based on |F| and resolution.
Hölzer
K
K
Institut für Kristallographie, Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany.
Weckert
E
E
Schroer
K
K
D000465:Algorithms; D000818:Animals; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D002645:Chickens; D003460:Crystallization; D018360:Crystallography, X-Ray; D003625:Data Collection; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D011487:Protein Conformation; D017356:Synchrotrons
D009113:Muramidase