Time-resolved scattering methods for biological samples at the CoSAXS beamline, MAX IV Laboratory.

Area of Science:

• Structural biology
• Biophysics
• Materials science

Background:

• CoSAXS is a cutting-edge SAXS/WAXS beamline at MAX IV, offering high brilliance for advanced research.
• Time-resolved scattering methods are crucial for understanding dynamic processes in biological and material systems.

Purpose of the Study:

• To showcase the capabilities of the CoSAXS beamline with four distinct sample environments.
• To demonstrate the application of millisecond time-resolved SAXS/WAXS for studying protein structural dynamics.

Main Methods:

• Utilizing a state-of-the-art SAXS/WAXS beamline (CoSAXS) at MAX IV.
• Employing four advanced sample environments: SUrF (SAXS with UV-vis and fluorescence), microfluidic chips, stopped-flow, and laser "pump-probe" setups.
• Coupling fast X-ray detectors with precise sample environment control for millisecond resolution.

Main Results:

• Successfully monitored protein conformational changes during acid-driven denaturation using the SUrF setup.
• Mapped concentration-dependent structural changes using microfluidic chips with minimal sample volume.
• Captured initial mixing effects at 2-millisecond timescales using stopped-flow SAXS.
• Investigated protein intermediate structures under light and temperature perturbations via laser pump-probe experiments.

Conclusions:

• CoSAXS facilitates high-resolution, millisecond time-resolved structural studies of proteins in solution.
• The demonstrated sample environments enable comprehensive investigations of dynamic structural processes.
• The beamline's stability and low background are key for extracting subtle structural features, including cooperative motions.