Compression of random coils due to macromolecular crowding: scaling effects

Area of Science:

• Polymer Physics
• Solution Behavior
• Statistical Mechanics

Background:

• Polymers in dilute solutions exhibit specific chain dimensions and interactions.
• Macromolecular crowding agents are used to mimic crowded cellular environments.
• Understanding polymer behavior under crowding is crucial for biological and materials science.

Purpose of the Study:

• To investigate the impact of size ratio between polymers and crowding agents on polymer chain compression.
• To quantify the effect of macromolecular crowding on the Flory exponent and polymer-polymer interactions.
• To determine how polymer molecular weight influences compression and aggregation under crowding conditions.

Main Methods:

• Theoretical study of polymer solutions with macromolecular crowding agents.
• Analysis of the effect of varying size ratios and crowding agent concentrations (Φ).
• Calculation of the Flory exponent ν(Φ) as a function of crowding concentration.

Main Results:

• Macromolecular crowding exerts compressive force on polymer chains, reducing their size.
• Compression effect is more pronounced at lower crowding agent concentrations for higher molecular weight polymers.
• The Flory exponent decreases from approximately 0.48 in dilute solution to 0.3 with crowding.
• Effective polymer-polymer interactions shift from repulsive to strongly attractive, inducing chain aggregation.
• These effects are significantly amplified for larger polymer sizes and higher molecular weights.

Conclusions:

• Macromolecular crowding fundamentally alters polymer chain conformation and interactions in solution.
• The size ratio and molecular weight are critical parameters governing the extent of polymer compression and aggregation.
• Crowding can induce polymer collapse and aggregation, mimicking phenomena observed in biological systems.