Observation of a single protein by ultrafast X-ray diffraction

Area of Science:

• Structural Biology
• Biophysics
• X-ray Science

Background:

• Crystallography is the standard for protein imaging but requires extensive sample preparation.
• X-ray free-electron lasers (XFELs) offer intense, ultrashort pulses for potential single-molecule imaging.
• Previous studies demonstrated diffraction before destruction on larger biological samples like viruses.

Purpose of the Study:

• To demonstrate X-ray diffraction from a single protein molecule.
• To image the smallest biological sample to date using X-rays.
• To validate the "diffraction before destruction" concept for single proteins.

Main Methods:

• Utilized ultrashort, high-intensity X-ray pulses from an XFEL.
• Focused on single molecules of Escherichia coli GroEL (14 nm diameter).
• Recorded diffraction patterns before sample destruction due to the intense pulse.

Main Results:

• Successfully obtained an X-ray diffraction pattern from a single Escherichia coli GroEL protein.
• Achieved imaging of the smallest biological sample (14 nm) by X-rays to date.
• Determined the approximate orientation of the imaged protein from its diffraction pattern.

Conclusions:

• The "diffraction before destruction" principle is applicable to single protein imaging.
• Ultrafast X-ray imaging of single proteins is feasible.
• This technique opens new avenues for femtosecond time-resolved single-molecule studies at room temperature.