MFX: Macromolecular Femtosecond Crystallography

The MFX hutch has specialized equipment for determining the structures of proteins, which carry out many vital functions in living things. A goniometer holds a single microscopic protein crystal and positions it in front of the X-ray beam. A robotic arm holds the detector, and another robot switches out one sample for another. Eventually scientists will be able to mail their samples to LCLS and control MFX experiments remotely, even from another state or country.

With many common X-ray tools, the radiation damages the sample before scientists can get a clear image. However, the X-ray laser pulses at LCLS are so short that the photons outrun the damage, allowing scientists to capture information about the sample’s atomic structure in the instant before it’s destroyed. This is known as “diffract before destroy” and it’s especially useful for radiation-sensitive samples, like the protein complexes involved in photosynthesis.

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The MFX (Macromolecular Femtosecond Crystallography) instrument primarily uses short pulses of X-rays to limit damage to samples during the exposure. This allows, for example, the study of metal-containing macromolecules that are particularly sensitive to radiation damage due to the high absorption of X-rays by the metal atoms.