Cryocrystallography of biological macromolecules: a generally applicable method.

Methods have been developed that allow facile X-ray data collection for biological macromolecules at cryogenic (near liquid N2) temperatures. The crystals are first transferred from their mother liquor to a hydrocarbon environment, then mounted with a standard glass fiber (no capillary), and flash cooled in situ with a cold nitrogen stream on the diffraction apparatus. This approach prevents freezing of the solvent in the crystals, so that they maintain their crystallographic integrity. Significant improvement of resolution can result from the cryogenic data collection, and radiation damage in the cooled crystals is greatly reduced, or eliminated, for the duration of data collection.