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Phasing protein structures

Phasing protein structures

Solve the phasing problem at home with Cr-radiation

The single-wavelength anomalous dispersion method (SAD) is frequently used to solve protein structures from synchrotron data by taking advantage of the tunable wavelength to collect heavy atom derivatives near the metal's absorption edge. For methionine-containing proteins, selenomethionine derivates may be prepared to take advantage of the anomalous Se signal.

However, some proteins will not crystallize as SeMet derivatives, and not all proteins contain methionine. Sulfur, on the other hand, is present in almost all proteins in cysteine residues. The process of structure solution is greatly simplified if SeMet substitution or heavy-atom soaks are not necessary.
The structure of crambin was solved in 1981 using the resolved atom S-SAD method and Cu Kα radiation and a number of other proteins have been solved using Cu or synchrotron radiation tuned to near-Cu wavelengths.

Rigaku recommends the following systems:


A customized single crystal X-ray diffraction system that has the capabilities of utilizing both ports of a rotating anode X-ray source.

A microfocus sealed tube single crystal X-ray diffractometer that is low maintenance and perfect for screening and evaluating protein crystals.

A single crystal X-ray diffractometer with high-flux microfocus rotating anode X-ray generator and direct detection, HPC X-ray detector.

A versatile and high-flux dual-wavelength (DW) X-ray diffractometer with an HPC X-ray detector for multipurpose diffraction experiments

Automated tool for performing in situ crystallography experiments on existing X-ray diffractometers

High-resolution X-ray detectors for X-ray diffractometers from DECTRIS

Automated crystal transport, orientation and retrieval robot


Single wavelength Confocal Max-Flux (CMF) optics for single crystal diffraction


Small angle X-ray scattering (SAXS) Kratky camera system

Small Molecule

User-inspired data collection and data processing software for small molecule and protein crystallography


A unique curved single crystal X-ray diffraction detector based on direct X-ray detection technology with the highest 2θ range at a single position available for the home lab.

Extremely low noise, air-cooled X-ray detector based on direct X-ray detection technology.