Anisotropic Picosecond X-ray Solution Scattering from Photo-selectively Aligned Protein Molecules

Area of Science:

• Biophysics
• Structural Biology
• X-ray Scattering

Background:

• Protein dynamics are crucial for biological function.
• Understanding molecular orientation provides insights into protein behavior.
• Transient molecular alignment can be induced by polarized light.

Purpose of the Study:

• To measure anisotropic X-ray scattering patterns from laser-excited myoglobin molecules.
• To investigate the orientational dynamics of myoglobin on a picosecond to microsecond timescale.
• To demonstrate the utility of pump-probe X-ray solution scattering for studying transiently aligned molecules.

Main Methods:

• Utilizing pump-probe X-ray solution scattering.
• Employing a linearly polarized laser pulse to excite myoglobin molecules.
• Measuring anisotropic X-ray scattering patterns at various time delays (100 ps to 1 µs).

Main Results:

• Anisotropic scattering patterns were obtained from photo-excited myoglobin at 100 ps.
• The temporal evolution of these patterns revealed orientational dynamics.
• A rotational diffusion time of approximately 15 ns was determined for photo-generated myoglobin.

Conclusions:

• Anisotropic X-ray scattering provides enhanced structural information compared to isotropic patterns.
• Pump-probe X-ray solution scattering is effective for studying transiently aligned molecules.
• The study successfully characterized the orientational dynamics of myoglobin post-laser excitation.