Biomolecular binding under confinement: statistical predictions of steric influence in the absence of long-distance interactions.

We propose here a theoretical model for the influence of confinement on biomolecular binding at the single-molecule scale at equilibrium, based on the change of the number of microstates (localization and orientation) upon reaction. Three cases studies are discussed: DNA sequences shorter and longer than the single strain DNA Kuhn length and spherical proteins, confined into a spherical container (liposome, droplet…). The results show that this influence is highly dependent on the molecular structure and significant for large molecules (relative to container size).