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Analytical Chemistry

Stanford’s Free Electron Laser Blasts Away

Here’s another next-generation X-ray crystal paper, this time using a free electron laser X-ray source. That’s powerful enough to cause very fast and significant radiation damage to any crystals you put in its way, so the team used a flow system, with a stream of small crystals of T. brucei cathepsin B enzyme being exposed in random orientations to very short pulses of extremely intense X-rays. (Here’s an earlier paper where the same team used this technique to obtain a structure of the Photosystem I complex). Note that this was done at room temperature, instead of cryogenically. The other key feature is that the crystals were actually those formed inside Sf9 insect cells via baculovirus overexpression, not purified protein that was then crystallized in vitro.
Nearly 4 million of these snapshots were obtained, with almost 300,000 of them showing diffraction. 60% of these were used to refine the structure, which out at 2.1 Angstroms, and clearly showed many useful features of the enzyme. (Like others in its class, it starts out inhibited by a propeptide, which is later cleaved – that’s one of the things that makes it a challenge to get an X-ray structure by traditional means).
I’m always happy to see bizarre new techniques used to generate X-ray structures. Although I’m well aware of their limitations, such structures are still tremendous opportunities to learn about protein functions and how our small molecules interact with them. I wrote about the instrument used in these papers here, before it came on line, and it’s good to see data coming out of it.

7 comments on “Stanford’s Free Electron Laser Blasts Away”

  1. Boghog says:

    also known as “diffraction before destruction”

  2. Brooks Moses says:

    Boghog @1: In this case, rather like “pillage, _then_ burn”.

  3. Vanzetti says:

    Ah, X-ray laser, also known as The Death Ray. Soon in an airborne cannon form?

  4. metaphysician says:

    Is the apparatus in question an actual x-ray laser? Or merely(?) an x-ray source that uses a laser to generate the rays?

  5. Paul says:

    #4: it uses high energy electrons from the Stanford Linear Accelerator Center to produce a very short pulse of coherent X-rays. It’s an x-ray frequency free electron laser.

  6. jbosch says:

    And it is an extremely powerful technique. In particular if one fails to produce useful crystals suitable for normal x-ray diffraction. The method seems to mature fairly quickly, however there are only very few facilities with these capabilities. I think the one in Hamburg will be completed in 2016 if I’m not wrong.
    Follow the link to a very good paper about the method:

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