Radiation damage in sub-Ångström resolution macromolecular crystallography: a low-dose study

Area of Science:

• Structural Biology
• Crystallography
• Biophysics

Background:

• Sub-ångström macromolecular crystallography enables detailed structural analysis without prior chemical knowledge.
• Potential quantum-mechanical phenomena and subtle structural deviations can be observed at this resolution.
• The impact of radiation damage on structural integrity at sub-ångström resolution was previously unknown.

Purpose of the Study:

• To investigate the effects of radiation damage on macromolecular structures at sub-ångström resolution.
• To quantify radiation damage effects on Pyrococcus abyssi rubredoxin at varying X-ray doses.
• To establish optimal data collection strategies for high-resolution structural studies.

Main Methods:

• Collected X-ray diffraction data from Pyrococcus abyssi rubredoxin crystals at 100 K.
• Analyzed structural changes at different radiation doses (50 kGy and 1 MGy).
• Utilized isomorphous difference maps to identify conformational alterations and density blurring.

Main Results:

• The oxidized Fe3+ state was largely preserved at 50 kGy but partially reduced to Fe2+ at 1 MGy.
• Extensive conformational changes, likely linked to iron reduction, were observed at 1 MGy.
• Hydrogen densities, visible at 50 kGy, were preserved but blurred at 1 MGy, indicating dose-dependent structural degradation.

Conclusions:

• Radiation damage at sub-ångström resolution causes both local and extended 'global' structural changes.
• Low-dose data collection with uniform beam profiles is essential for accurate sub-ångström structural investigations.
• The concept of 'resolution in dose' is proposed to characterize the ability to resolve progressive radiation damage details.