An optimal exposure strategy for cryoprotected virus crystals with lattice constants greater than 1000 A.
Studies of icosahedral virus capsids provide insights into the function of supramolecular machines. Virus capsid crystals have exceptionally large unit cells; as a result, they diffract weakly compared with protein crystals. HK97 is a dsDNA lambda-like bacteriophage whose 13 MDa capsid expands from 550 A to 650 A with large subunit conformational changes during virus maturation. The HK97 penultimate maturation intermediate was crystallized in a tetragonal unit cell that has lattice constants of 1010 A x 1010 A x 730 A. The crystals could be cryoprotected, but diffracted to a modest resolution of 5 A at a bending-magnet beamline. When these crystals were optimally exposed with two orders-of-magnitude more photons from a new insertion-device beamline, data extending to better than 3.8 A resolution were obtained. Here, the strategies to collect and process such data are described. These strategies can be adapted for other crystals with large unit cells and for microcrystals.
Gan
Lu
L
The Scripps Research Institute, USA.
Johnson
John E
JE
D001435:Bacteriophages / Q000737:chemistry*; D002213:Capsid / Q000737:chemistry*; D003460:Crystallization