Visualizing a protein quake with time-resolved X-ray scattering at a free-electron laser

Area of Science:

• Biophysics
• Structural Biology
• Photochemistry

Background:

• Proteins undergo conformational changes crucial for their function.
• Understanding ultrafast dynamics is key to elucidating biological mechanisms.
• Energy dissipation pathways in proteins remain incompletely understood.

Purpose of the Study:

• To develop and demonstrate a method for measuring ultrafast protein structural changes.
• To investigate the initial structural dynamics following photoexcitation in a protein.
• To provide structural evidence for the 'protein quake' hypothesis.

Main Methods:

• Utilized time-resolved wide-angle X-ray scattering (TR-WAXS).
• Employed an X-ray free-electron laser (XFEL) for high temporal resolution.
• Used multiphoton excitation of the Blastochloris viridis photosynthetic reaction center.

Main Results:

• Observed an ultrafast global conformational change within picoseconds.
• This structural change preceded heat propagation through the protein.
• Provided direct structural evidence supporting the 'protein quake' mechanism.

Conclusions:

• The developed TR-WAXS method is effective for studying ultrafast protein dynamics.
• Proteins can dissipate energy rapidly through quake-like motions.
• This mechanism plays a role in the initial response to photoexcitation.