Unusual size-dependence of effective interactions between collapsed polymers in crowded environments

Area of Science:

• Polymer Physics
• Biophysics
• Computational Chemistry

Background:

• Macromolecular crowding is prevalent in biological systems.
• Understanding interactions in crowded environments is crucial for biomolecular behavior.
• Conventional models often rely on depletion attraction between hard spheres.

Purpose of the Study:

• To investigate the effect of macromolecular crowding on collapsed polymer interactions.
• To provide insights into biomacromolecular interactions within crowded biological settings.
• To explore the size-dependence of effective attractions.

Main Methods:

• Utilizing computer simulations to model polymer-crowder systems.
• Analyzing effective interactions between collapsed polymers under crowding conditions.
• Deconstructing interactions into polymer-mediated repulsion and crowder-mediated attraction.

Main Results:

• Macromolecular crowding induces effective attraction between collapsed polymers.
• Attraction strength decreases with reduced crowder size at fixed volume fraction.
• This size-dependence contrasts with depletion attraction in hard-sphere colloids.
• Overlapping repulsive and attractive interaction ranges due to flexible polymer boundaries cause partial cancellation.

Conclusions:

• Effective interactions in crowded biological environments can differ from hard-sphere depletion models.
• The flexibility of biomacromolecules leads to unique size-dependent interaction effects.
• Findings suggest a revised understanding of biomacromolecular assembly and function in vivo.