Common methods to obtain initial experimental phases
Isomorphous Replacement (MIR)
•At least one native and 2 crystals soaked with
heavy metal solution must be available. Good phasing power,
can be done in-house. Non-isomorphism limits phases to lower
Single Anomalous Diffraction
•At least one crystal
containing a suitable anomalously scattering element must be available. Combined
with Solvent Modification techniques. Good phasing power, works in-house for some elements
including native Sulfur. Most prominent phasing technique.
Anomalous Dispersion (MAD)
•An anomalous scatterer
must be present and several data sets must be collected at varying wavelengths.
Requires a synchrotron and careful data collection. Excellent phases
to high resolution from highly isomorphous Se-Met crystals.