Related Experiment Videos
How does radiation damage in protein crystals depend on X-ray dose?
Piotr Sliz1, Stephen C Harrison, Gerd Rosenbaum
1Department of Biological Chemistry and Molecular Pharmacology, Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02115, USA.
Structure (London, England : 1993)
|January 9, 2003
Summary
Radiation damage to cryopreserved protein crystals is proportional to dose at high-flux synchrotron sources. Approximately ten absorbed photons can damage a unit cell, limiting crystal size for data collection.
Area of Science:
- Structural biology
- X-ray crystallography
- Synchrotron radiation science
Background:
- Cryopreserved protein crystals are vital for structural determination.
- High-flux synchrotron sources enable detailed analysis but raise concerns about radiation damage.
Purpose of the Study:
- To investigate the relationship between accumulated radiation dose and damage in cryopreserved protein crystals.
- To determine the photon flux density threshold at which damage becomes significant.
Main Methods:
- Irradiation of various protein crystals with high-flux X-rays at third-generation synchrotron sources (APS beamline 19-ID).
- Measurement of absorbed photon dose and correlation with crystal damage.
- Analysis of diffraction data to determine unit cell integrity and resolution limits.
Main Results:
- Radiation damage is strictly proportional to accumulated dose, even at high flux densities (up to 10(15) ph/sec/mm(2)).
- Approximately ten absorbed photons are sufficient to damage a protein crystal unit cell at 12 keV.
- Each unit cell can contribute only about one photon to Bragg diffraction due to damage.
Conclusions:
- The findings confirm a linear relationship between radiation dose and damage in protein crystallography.
- The study establishes a critical photon absorption limit per unit cell for data collection.
- The minimum crystal size for a 3.5 A resolution data set is estimated to be around 20 micrometers.