Intermolecular electrostatic interactions and Brownian tumbling in protein solutions

Area of Science:

• Biophysics
• Physical Chemistry
• Structural Biology

Background:

• Intermolecular electrostatic interactions are often assumed negligible or solely decelerating for protein Brownian tumbling.
• The shape of the rotational auto-correlation function is typically not considered affected by these interactions.

Purpose of the Study:

• To review experimental and simulation data on the role of electrostatic interactions in protein rotational dynamics.
• To demonstrate that interprotein electrostatic steering complicates the rotational correlation function.

Main Methods:

• Nuclear Magnetic Resonance (NMR) relaxation measurements.
• Dielectric spectroscopy.
• Brownian dynamics simulations.

Main Results:

• Experimental data and simulations show that interprotein electrostatic steering significantly affects protein rotational dynamics.
• This steering induces rotational anisotropy due to protein dipole moments interacting with neighboring protein charges.
• The rotational auto-correlation function's shape is altered, not just its speed.

Conclusions:

• Electrostatic interactions play a crucial role in the rotational dynamics of proteins in solution.
• The observed complications in the rotational correlation function are critical for accurate interpretation of experimental data.
• Considering interprotein electrostatic steering is essential for understanding protein solution behavior.