Hanging Drop Sitting Drop Microdialysis Crystallization Screening.

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Presentation transcript:

Hanging Drop Sitting Drop Microdialysis Crystallization Screening

X-ray Source: x-ray tubes, rotating anode tubes, or particle storage rings Gonoimeter Detectors: X-ray films, CCD cameras, or Multiwire detectors.

The diffraction data does not give the phase angle that is needed to calculate the electron density map. Have to get the phase angle through other methods. Isomorphous Replacement: Insert a heavy metal atom into crystal protein, and locate in diffraction pattern and in the cell. Use the location of metal ion to find the phase angle for the other protein atoms. Requirements: Add atom with same unit cell size. Cannot disturb protein structure.

Small molecules (up to 300 atoms) usually form more ordered crystals than large molecules, it is possible to attain lower R- factors. In the Cambridge Structural Database more than 95% of the 500,000+ crystals have an R-factor lower than 0.15 and 9.5% have an R-factor lower than 0.03.Cambridge Structural Database The calculated R-factor = reliability factor; measure of convergence between the intensities given off by your model and the observed intensities. determines the resolution of the model (less than 2 angstroms is good) R factors generally are in the range of 0.05 to 0.2 for proteins which

Steps of Protein X-ray Crystallography: Crystallize your protein. Cryo-freeze your protein. Do an X-ray diffraction. Make a heavy atom derivative of protein. Take X-ray diffraction of the derivative. Do a Fourier Transform (or let a computer do it). Create models. Check R-Factor of models.