Carp Muscle Calcium-binding Protein

The tangent formula for crystallographic phase determination has been used to refine and extend the phase information for the crystal structure of carp muscle calcium-binding protein. Phases from the multiple isomorphous replacement analysis were used to initiate the tangent formula calculations. New phases were developed in a cautious, gradual procedure which continued to emphasize the isomorphous replacement data. Probability measures were instrumental in combining the phase information from the tangent formula with that from isomorphous replacement. The new electron density map which finally resulted showed a more highly resolved and readily interpreted image of the molecule than was evident in earlier maps. Most importantly, the new map permitted the interpretation of a second calcium-binding site.