Application of the molecular replacement method to a heavy-atom problem

The molecular replacement method has been applied to the heavy-atom problem in a case for which a heavy-atom model existed for one crystal form, and both native and derivative data were available for another crystal form of the same molecule; the absolute values of difference amplitudes for the second form were used in the calculation. The key requirement for obtaining a solution is that the contents of the asymmetric unit are the same and the same heavy-atom compound is used in both cases.