Structure-factor analysis of femtosecond microdiffraction patterns from protein nanocrystals
Richard A Kirian1, Thomas A White, James M Holton
1Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
Acta Crystallographica. Section A, Foundations of Crystallography
|February 18, 2011
Summary
Researchers extracted structure factors from nanocrystals using X-ray microdiffraction. This method enables efficient data collection from small crystals, crucial for structural biology and time-resolved studies.
Area of Science:
- Structural Biology
- Crystallography
- Biophysics
Background:
- Determining protein structures is vital for understanding biological functions.
- Traditional X-ray crystallography requires large, high-quality crystals, which are often difficult to obtain.
- Nanocrystals offer an alternative but present challenges in data collection and analysis.
Purpose of the Study:
- To develop and validate a method for extracting complete structure factors from randomly oriented nanocrystals.
- To assess the feasibility of using femtosecond X-ray diffraction data from nanocrystals for structural determination.
- To compare the quality of data obtained from nanocrystals with that from large single crystals.
Main Methods:
- Collected hundreds of thousands of femtosecond single-shot X-ray microdiffraction patterns from Photosystem I nanocrystals.
- Applied Monte Carlo integration to account for crystallite size and orientation.
- Utilized a hydrated protein nanocrystal injector jet at the Linac Coherent Light Source (LCLS).
- Analyzed single diffraction snapshots from nanocrystals ranging from 100 nm to 2 µm.
Main Results:
- Successfully extracted a complete set of structure factors from randomly oriented nanocrystals.
- Demonstrated that the Monte Carlo method can determine structure factors without prior knowledge of particle-size distribution.
- Found the quality of data from nanocrystals to be comparable to data from large single crystals.
- Observed that crystal-size effects dominated the angular width of Bragg peaks.
Conclusions:
- The developed method significantly improves data collection efficiency by enabling the use of very small protein crystals.
- This approach has implications for reducing radiation damage and facilitating time-resolved diffraction studies at room temperature.
- The findings open new avenues for structural analysis of proteins that are challenging to crystallize in large forms.
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