Radiation damage of protein crystals at cryogenic temperatures between 40 K and 150 K.

X-ray radiation damage of lysozyme single crystals by an intense monochromatic beam from the Advanced Photon Source is studied at cryogenic temperatures between 40 K and 150 K. The results confirm that primary radiation damage is both linearly dependent on the X-ray dose and independent of temperature. The upper limit for the primary radiation damage observed in our previous study [Teng & Moffat (2000), J. Synchrotron Rad. 7, 313-317] holds over the wider temperature range of this study. The X-ray diffraction quality of the data acquired at 40 K is superior to those at 100 K, apparently due to temperature dependence of secondary and tertiary radiation damage and to reduced thermal motion.