Single-particle imaging by x-ray free-electron lasers-How many snapshots are needed?

Area of Science:

• Structural biology
• Biophysics
• X-ray science

Background:

• X-ray free-electron lasers (XFELs) provide intense, ultrashort X-ray pulses.
• These pulses allow diffraction data collection before sample destruction.
• Single-particle imaging reconstructs molecular structures from limited data.

Purpose of the Study:

• To estimate the number of diffraction patterns required for 3D electron density reconstruction.
• To assess the feasibility of achieving sub-nanometer resolution.
• To validate the estimate using simulations under realistic XFEL conditions.

Main Methods:

• Simulations of XFEL experiments.
• Analysis of diffraction data from single biological macromolecules.
• Bacterial phytochrome used as a model system.

Main Results:

• An estimate for the number of diffraction patterns needed for targeted resolution was determined.
• Simulations confirmed the estimate's validity for modern XFELs.
• Sub-nanometer resolution was demonstrated as achievable.

Conclusions:

• XFELs are powerful tools for single-particle structure determination.
• The number of diffraction patterns is critical for reconstruction quality.
• Sub-nanometer resolution imaging of biological macromolecules is feasible.