Phasing coherently illuminated nanocrystals bounded by partial unit cells.

Area of Science:

• Structural Biology
• Biophysics
• Crystallography

Background:

• Free-electron lasers (FELs) provide femtosecond X-ray pulses, enabling high-resolution diffraction data collection from protein nanocrystals.
• Conventional crystallography faces limitations with small or incomplete crystals, hindering phase retrieval.

Purpose of the Study:

• To extend phase retrieval methods using FEL diffraction data to nanocrystals with partial unit cells due to random edge terminations.
• To reformulate and address the phase problem for such challenging crystal systems.

Main Methods:

• Utilizing highly coherent femtosecond X-ray pulses from an FEL to record diffraction patterns.
• Developing and applying iterative algorithms for phase retrieval from nanocrystal diffraction data.
• Investigating nanocrystals with random edge terminations and partial unit cells.

Main Results:

• Demonstrated that FEL diffraction data contains more information than conventional data.
• Successfully reformulated the phase problem for nanocrystals lacking a common repeating unit cell.
• Provided an approximate solution for the phase problem in crystals with random edge terminations.

Conclusions:

• The developed approach allows for phase retrieval from challenging nanocrystal samples.
• This method enhances the potential of FELs for determining protein structures from limited or imperfect crystals.
• Advances in solving the phase problem open new avenues in structural biology.