Too Close for Comfort: Depletion Forces Beyond Excluded Volume

Crowding is ubiquitous in biological and soft matter systems, where the proximity of macromolecules reshapes their interactions, stability, and assembly. Classical depletion theory treats these effects as entropy-driven consequences of excluded volume: crowders generate effective attractions by increasing the free volume available to the surrounding solution. Yet many biological and polymeric crowders are soft, chemically specific, and solvent-coupled, so their effects can include substantial energetic contributions.

In this talk, I will discuss how polymers and other crowders influence protein folding and oligomerization beyond idealized hard-particle models. I will present theoretical developments that incorporate soft interactions, crowder properties, and polymer scaling, leading to a broader physical picture of depletion forces in complex molecular environments.