Journal
ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY
Volume 66, Issue -, Pages 1092-1100Publisher
INT UNION CRYSTALLOGRAPHY
DOI: 10.1107/S0907444910035523
Keywords
protein crystallography; radiation damage; temperature dependence; glass transition
Funding
- National Institutes of Health (NIH) [GM065981-05 A1]
- National Science Foundation (NSF)
- NIH/National Institute of General Medical Sciences under NSF [DMR-0225180]
- NIH through National Center for Research Resources [RR-01646]
Ask authors/readers for more resources
The temperature-dependence of radiation damage to thaumatin crystals between T = 300 and 100 K is reported. The amount of damage for a given dose decreases sharply as the temperature decreases from 300 to 220 K and then decreases more gradually on further cooling below the protein-solvent glass transition. Two regimes of temperature-activated behavior were observed. At temperatures above similar to 200 K the activation energy of 18.0 kJ mol-1 indicates that radiation damage is dominated by diffusive motions in the protein and solvent. At temperatures below similar to 200 K the activation energy is only 1.00 kJ mol-1, which is of the order of the thermal energy. Similar activation energies describe the temperature-dependence of radiation damage to a variety of solvent-free small-molecule organic crystals over the temperature range T = 300-80 K. It is suggested that radiation damage in this regime is vibrationally assisted and that the freezing-out of amino-acid scale vibrations contributes to the very weak temperature-dependence of radiation damage below similar to 80 K. Analysis using the radiation-damage model of Blake and Phillips [Blake & Phillips (1962), Biological Effects of Ionizing Radiation at the Molecular Level, pp. 183-191] indicates that large-scale conformational and molecular motions are frozen out below T = 200 K but become increasingly prevalent and make an increasing contribution to damage at higher temperatures. Possible alternative mechanisms for radiation damage involving the formation of hydrogen-gas bubbles are discussed and discounted. These results have implications for mechanistic studies of proteins and for studies of the protein glass transition. They also suggest that data collection at T similar or equal to 220 K may provide a viable alternative for structure determination when cooling-induced disorder at T = 100 is excessive.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available