Microfabricated mounts for high-throughput macromolecular cryocrystallography

A new approach is described for mounting microcrystals of biological macromolecules for cryocrystallography. The sample mounts are prepared by patterning thin polyimide films by standard microfabrication techniques. The patterned structures contain a small hole for the crystal connected to a larger hole via a drainage channel, allowing removal of excess liquid and easier manipulation in viscous solutions. These polyimide structures are wrapped around small metal rods. The resulting curvature increases their rigidity and allows a convenient scoop-like action in retrieving crystals. The polyimide contributes minimally to X-ray background and absorption, and can be treated to obtain desired hydrophobicity or hydrophilicity. The new mounts are fully compatible with existing automated sample-handling hardware for cryocrystallography. Their potential advantages include completely reproducible sample hole sizes to below 10 µm; accurate and reproducible sample positioning and good sample-to-mount contrast, simplifying alignment; more convenient manipulation of small crystals; easier removal of excess liquid and reduced background scatter; reduced thermal mass and more rapid flash-cooling; and easy design customization and mass production. They are especially well suited to data collection from the smaller crystals produced in high-throughput crystallization trials, and are suitable for automated crystal retrieval. They should be more generally useful for X-ray data collection from small organic and inorganic crystals of all types.