Structure and interactions of aggrecans: statistical thermodynamic approach

Area of Science:

• Biophysics
• Polymer Science
• Materials Science

Background:

• Aggrecan molecules are key components of cartilage, influencing its mechanical properties.
• Weak polyelectrolytes tethered to surfaces serve as a model for aggrecan behavior.
• Understanding aggrecan interactions is crucial for explaining cartilage function.

Purpose of the Study:

• To investigate the structural and thermodynamical properties of interacting aggrecan molecules.
• To explore the effects of acidity (pH) and salt concentration on aggrecan behavior.
• To model the influence of molecular properties like conformation, size, shape, and charge distribution.

Main Methods:

• Utilized molecular density functional theory.
• Incorporated acid-base equilibrium into the theoretical model.
• Analyzed conformations, size, shape, and charge distribution of molecular species.

Main Results:

• Repulsive interactions between aggrecan molecules are significantly affected by salt concentration and pH.
• Increased acidity and decreased salt concentration lead to larger and longer-range repulsive forces.
• Higher pH increases molecular charge, enhancing repulsion and reducing interdigitation.

Conclusions:

• The size and range of aggrecan forces explain their aggregation and ability to resist compression in cartilage.
• Low interdigitation in charged polyelectrolyte layers, like those in cartilage, contributes to excellent lubrication properties.