Substructure determination in multiwavelength anomalous diffraction, single anomalous diffraction, and single...

Area of Science:

• Structural Biology
• Crystallography
• Biophysical Chemistry

Background:

• Accurate substructure determination is crucial for solving the phase problem in X-ray crystallography.
• Selenium and sulfur atoms are commonly used as heavy atom derivatives for phasing.
• Existing methods may have limitations in scope or applicability for different experimental setups.

Purpose of the Study:

• To present a general and robust method for selenium and sulfur substructure determination.
• To demonstrate the utility of the Shake-and-Bake (SnB) algorithm for this purpose.
• To provide a protocol applicable to various anomalous diffraction and isomorphous replacement datasets.

Main Methods:

• Utilized the Shake-and-Bake (SnB) algorithm.
• Employed anomalous difference E magnitudes derived from experimental data.
• Adapted the protocol for multiwavelength anomalous diffraction (MAD), single anomalous diffraction (SAD), and single isomorphous replacement with anomalous scattering (SIRAS) data.

Main Results:

• Successfully demonstrated a general method for substructure determination of selenium and sulfur.
• The SnB algorithm in conjunction with anomalous differences proved effective.
• The protocol showed applicability to Se-Met MAD, Se-Met SAD, S-SAD, and S/Se-SIRAS experiments.

Conclusions:

• The presented Shake-and-Bake based protocol offers a versatile approach for selenium and sulfur substructure determination.
• This method can be readily applied to various heavy atom derivative datasets, including halides with minor modifications.
• The findings facilitate structure solution in crystallography, particularly when dealing with sulfur- and selenium-containing macromolecules.