Matthew A. Warkentin, and Robert E. Thorne
Physics Department,
Cornell
University
Abstract:
We have measured unit cell parameters, mosaicities, B-factors, crystal perfection, and radiation sensitivity for four
model systems -- Lysozyme, Trypsin, Thaumatin and Ribonuclease A -- as a function of temperature. Unlike in
previous temperature-dependent studies, data is continuously collected from an individual crystal as it cools from 300
K to 100 K. B factors and mosaicity increase and large scale crystal perfection (as probed by X-ray topography)
degrades between 240 K and 180 K. These parameters show more modest evolution between 180 K and 100 K,
where solvent and protein motions have frozen out. Similarly, most of the decrease in radiation sensitivity occurs
between 240 K to 180 K. This confirms that the glass transition in the solvent + mobile protein system is responsible
for the dramatically increased crystal lifetimes at 100 K. Radiation damage studies may thus allow quantitative study
of solvent and protein motions.
2009 Run
Sept. 23rd to Nov. 10th
