Xenon Anomalous Diffraction Protocols

Diffraction data for
Cp1-Xe was collected remotely from the Stanford Synchrotron Radiation
Light source (SSRL) on beamline 12-2 with a DECTRIS Pilatus 6 M detector.
Reference sets of 1440 diffraction images were collected at 12999.97
eV with an oscillation angle of 0.25° over 360° rotation.
To confirm the identity of the Xe sites, diffraction data were also
collected at 6690.11 eV using the same strategy. Although well above
the L-edge, Xe exhibits significant anomalous scattering at this energy
with Δf″ ≈ 10 electrons. Diffraction
data for Av1-Xe was collected in-house on a Rigaku MicroMax 007-HF
X-ray generator with a Rigaku RAXIS-IV++ detector. All data sets were
integrated with the XDS program package.^{38 (link)} Scaling was carried out with the CCP4 suite,^{39 (link)} and phasing was determined by molecular replacement against
Av1 (PDB ID 3U7Q) and Cp1 (4WES).^{36 (link),40 (link)} Initial refinement was carried out with
CNS,^{41 (link)} and alternative conformations and
isotropic B-factors were refined with REFMAC5.^{42 (link),43 (link)} Simulated annealing was performed using PHENIX.^{44 (link)}