Powder diffraction from a continuous microjet of submicrometer protein crystals.

Area of Science:

• Structural biology
• Biophysics
• Crystallography

Background:

• Atomic-resolution protein structures are determined using powder diffraction and Rietveld refinement.
• Previous methods for protein powder diffraction involved batch samples, long X-ray exposure, and radiation damage.

Purpose of the Study:

• To demonstrate the feasibility of obtaining protein powder diffraction data from nanocrystals using a continuous microjet system.
• To present the first powder diffraction patterns from the membrane protein photosystem I using this new technique.

Main Methods:

• Development of a flow-focusing aerojet to deliver hydrated protein nanocrystals to an X-ray beam.
• Utilizing a continuous microjet system to avoid sample crushing and radiation damage.
• Recording powder diffraction patterns from photosystem I nanocrystals with crystallite sizes < 500 nm.

Main Results:

• Successful acquisition of preliminary powder diffraction patterns from photosystem I nanocrystals.
• Observed lowest-order reflections quantitatively agree with theoretical powder profile calculations.
• Validated the aerojet injector system for X-ray diffraction applications.

Conclusions:

• The continuous microjet method is a viable approach for collecting protein powder diffraction data from nanocrystals.
• This technique eliminates the need for sample crushing and cryocooling, mitigating radiation damage.
• The system shows promise for future applications in femtosecond diffraction and serial crystallography.