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It seems essentially all protein X-ray diffraction structures are obtained with flash-cooled protein crystals (in a stream of very cold gas). I’m curious if the diffraction pattern would be significantly different from the same crystal at room temperature (from thermal expansion, but not only - it may favor different conformations, and also flash cooling may disorder parts of the crystal).

What are some of the reasons that X-ray diffraction uses cooled crystals? Is it possible to do the same experiment with a room temperature crystal? Has this been done before, and what happens?

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  • $\begingroup$ I don't know but I think it would have something to do with vibrations in the structure at room temp vs low temps. A la Brownian motion. $\endgroup$
    – bob1
    2 days ago
  • $\begingroup$ Please read the help on asking questions. You will see you are required to do some research before posting and show evidence of this in your question. A simple Google search ("why are crystals cooled for protein x-ray crystallography?") gives an immediate answer. And asking whether anyone has tried it at room temperature. Really! $\endgroup$
    – David
    2 days ago
  • $\begingroup$ @David Why not answer the question rather than try to police question quality? I did do a number of searches; I just did it on pubmed, and the results were all about how to make crystals. I also looked through recent structures on rcsb.org and they were all cooled. $\endgroup$
    – Alex I
    2 days ago
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    $\begingroup$ Because it lowers the quality of the site. As an educator I try not to feed people with answers, but teach them how to answer questions themselves, even if they do not thank me for it. $\endgroup$
    – David
    2 days ago

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While protein diffraction data is nowadays most often collected in cryogenic temperatures, the room temperature crystallography also exists and you can find thousands of datasets in the PDB that were collected in 300K. The main reason for cryo-cooling is that it slows down radiation damage.

You can find in-depth discussion of both options in the literature. I just quickly googled it and found two review articles about advantages of cryo- and room temperature crystallography:

Cryo-cooling in macromolecular crystallography: advantages, disadvantages and optimization

Macromolecular room temperature crystallography

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