APPLICATION OF KNOWN TRIPLET PHASES IN THE CRYSTALLOGRAPHIC STUDY OF BOVINE PANCREATIC TRYPSIN-INHIBITOR - II - STUDY AT 2.0 ANGSTROM RESOLUTION

Direct methods strengthened by the application of about 130 triplet ph ases, assumed known with a mean error of about +/-20 degrees, were use d to re-determine the structure of BPTI with data at 2.0 Angstrom reso lution. The triplet phases served to shift the mean direction and enha nce the concentration parameter in the corresponding Cochran distribut ions. These phases were used in combination with the partial structure extracted from successive density maps to control the gradual expansi on and refinement of Fourier coefficients. Single phases were develope d iteratively from tangent-formula estimation following the path of th e convergence map. The a priori triplet-phase information was sufficie nt to initiate solution of the structure at 2.0 Angstrom.