The Link to X-Ray Protein Crystallography

A. Crystal Production

(wet lab)

  1. Production
  2. Purification
  3. Crystallisation

 
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B. Data Collection

(x-ray lab)

  1. Mounting
  2. Shooting
  3. Detection

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C. Structure Solution

(computer lab)

  1. Indexing
  2. Integration
  3. Scaling
  4. Phasing
  5. Building
  6. Refinement
  7. Validation
  8. Publication

Molecular Replacement (MR)

If a homologous protein structure with a sequence of sufficient identity (preferrably at least 40%) is know n, this can be used to approximate the initial phases of the structure factors. For that purpose a Patterson map is calculated from the experimental intensities and compared to a theoretical Patterson map of the homologous structure coordinates. In Patterson maps all phases are set to 0 which results in a density that corresponds where the peaks correspond to distance vectors between individual atoms. By rotating and then translating the Patterson maps relative to each other the position of the molecules can be found and initial phases determined.

PROGRAMMES

Molrep
Phaser
Balbes (automated)
Mr Bump (automated)

LINKS

CIMR Protein Crystallography Course (molecular replacement)
Dima Chirgadze's Home Page
Biochem609 Tutorial
John Cooper's Home Page

OTHER METHODS

Direct methods (work only for small molecules)
Isomorphous replacement (SIR, MIR)
Anomalous dispersion (SAD, MAD)
Combination of methods (SIRAS, MIRAS)

Mission / Organisations / Trivia / Links / Florian Fisch / 16 June 2009