IMPROVING DIRECT-METHODS PHASES BY HEAVY-ATOM INFORMATION AND SOLVENTFLATTENING

In a recent series of papers, a procedure has been described for phasi ng all the reflections up to derivative resolution by using triplet ph ase relationships [Giacovazzo, Cascarano & Zheng (1988). Acta Cryst. A 44, 45-51]. The resulting electron-density maps show good correlation with the correct maps but usually are not straightforwardly interpreta ble. In this paper, the quality of the phases is improved by: (a) expl oiting the information on the heavy-atom structure, which becomes avai lable as soon as protein phases are available; (b) applying a suitable solvent-flattening procedure (FLEX), which proves highly effective in reducing the phase error.