Journal of Synchrotron Radiation

Volume 15, Part 3 (May 2008)

diffraction structural biology

J. Synchrotron Rad. (2008). 15, 223-226 [ doi:10.1107/S0909049507064813 ]

An optimal exposure strategy for cryoprotected virus crystals with lattice constants greater than 1000 Å

L. Gan and J. E. Johnson

Abstract: 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 Å to 650 Å 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 Å × 1010 Å × 730 Å. The crystals could be cryoprotected, but diffracted to a modest resolution of 5 Å 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 Å 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.

Keywords: virus crystals; bacteriophage HK97; insertion-device beamlines.