Journal of Applied Crystallography

Volume 35, Part 2 (April 2002)

research papers

J. Appl. Cryst. (2002). 35, 261-266 [ doi:10.1107/S0021889802002509 ]

Phasing possibilities using different wavelengths with a xenon derivative

S. Panjikar and P. A. Tucker

Abstract: Xenon derivatives are generally expected to be isomorphous with the native; however, the K- and L-absorption edges are not easily accessible on most synchrotron beamlines, which might limit their usefulness in phase determination. Various phasing procedures for xenon-derivatized porcine pancreatic elastase have been investigated using data sets measured at three generally accessible wavelengths. The importance of highly redundant data in measuring precise anomalous differences is highlighted and it is shown that, after such measurements, a single isomorphous replacement anomalous scattering (SIRAS) procedure yields a better phase set than those generated by single anomalous scattering (SAS) or multiwavelength anomalous diffraction (MAD) procedures.

Keywords: multiple isomorphous replacement anomalous scattering; SIRAS; SAS; MAD; macromolecular crystallography; protein crystallography; xenon-derivatized porcine pancreatic elastase.