Minimal Coarse-Grained Model for Immunoglobulin G: Diffusion and Binding under Crowding.

Area of Science:

• Biophysics
• Immunology
• Computational Biology

Background:

• Immunoglobulin G (IgG) is crucial for immune response in extracellular fluids.
• Limited research exists on IgG-antigen binding dynamics under physiological crowding.

Purpose of the Study:

• To investigate the effects of macromolecular crowding on IgG dynamics and binding kinetics.
• To develop a minimal coarse-grained model for IgG simulations.

Main Methods:

• Developed a six-bead coarse-grained IgG model.
• Utilized Brownian dynamics simulations.
• Compared IgG diffusion and flexibility with and without crowders.

Main Results:

• Macromolecular crowding slightly affects IgG flexibility.
• Crowders reduce IgG translational diffusion less than expected, possibly due to conformational changes.
• Crowding decreases the rate of the first IgG-antigen binding step and enhances the second.

Conclusions:

• IgG's flexibility is robust to macromolecular crowding.
• Crowding influences IgG diffusion and binding kinetics in complex ways.
• The developed IgG model accurately captures flexibility and diffusion properties.