Neutron spin echo studies on ferritin: free-particle diffusion and interacting solutions

Area of Science:

• Protein dynamics
• Biophysics
• Neutron scattering techniques

Background:

• Protein dynamics are crucial for biological function.
• Quasielastic neutron scattering (QENS) is a powerful tool for studying protein motion.
• Neutron spin echo (NSE) offers unique capabilities for probing dynamics over specific length scales.

Purpose of the Study:

• To systematically investigate the diffusive dynamics of ferritin and apoferritin using NSE.
• To analyze the influence of concentration and salt on protein diffusion.
• To compare different data analysis methods for NSE.

Main Methods:

• Neutron spin echo (NSE) experiments on ferritin and apoferritin solutions.
• Application of advanced fitting functions for NSE data analysis.
• Systematic variation of protein concentration and salt concentration.

Main Results:

• In dilute solutions, apoferritin diffusion matches theoretical predictions and its shell diameter (12.2 nm).
• Interacting ferritin solutions exhibit dynamics dominated by slowing down.
• Low-salt conditions induce molecular ordering, evidenced by a structure factor peak.

Conclusions:

• NSE is effective for studying protein diffusion and interactions.
• Protein-protein interactions significantly alter dynamics, leading to slower diffusion and ordering.
• Understanding these dynamics is key to comprehending protein solution behavior.