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Macromolecular diffusion in crowded media beyond the hard-sphere model

P. M. Blanco, J. L. Garcés, S. Madurga, F. Mas.
Soft Matter 14 (2018) 3105-3114.

Outline of the Chain Entanglement Soft-Core (CESC) model. Macromolecules are modeled as spheres with two different shells. The outer (transparent) accounts for the interaction between branches and the inner (opaque) accounts for the increasing steric repulsion.

The effect of macromolecular crowding in diffusion beyond the hard-core sphere model is studied. A new soft-core sphere model is presented, the Chain Entanglement Soft Potential (CESP) model, which considers the macromolecular flexibility and chain entanglement. CESP model uses a shoulder-shaped interaction potential which is implemented in the Brownian Dynamics (BD) computations. The interaction potential contains only one parameter associated to the chain entanglement energetic cost (Ur). The model is used to analyse the diffusion of streptavidin among different sized dextran obstacles. The obtained long-time diffusion coefficient Dlong values show better quantitative agreement to experiments than those obtained with hardcore spheres. CESP model is also able to quantitatively predict Dlong and the anomalous exponent for streptavidin diffusion.