Macromolecular diffusion in crowded media beyond the hard-sphere model

作者：Blanco Pablo M^*; Lluis Garces Josep; Madurga Sergio^*; Mas Francesc

来源：Soft Matter, 2018, 14(16): 3105-3114.

DOI：10.1039/c8sm00201k

The effect of macromolecular crowding on diffusion beyond the hard-core sphere model is studied. A new coarse-grained model is presented, the Chain Entanglement Softened Potential (CESP) model, which takes into account the macromolecular flexibility and chain entanglement. The CESP model uses a shoulder-shaped interaction potential that is implemented in the Brownian Dynamics (BD) computations. The interaction potential contains only one parameter associated with the chain entanglement energetic cost (U-r). The hydrodynamic interactions are included in the BD computations via Tokuyama mean-field equations. The model is used to analyze the diffusion of a streptavidin protein among different sized dextran obstacles. For this system, U-r is obtained by fitting the streptavidin experimental long-time diffusion coefficient D(long)versus the macromolecular concentration for D50 (indicating their molecular weight in kg mol(-1)) dextran obstacles. The obtained D-long values show better quantitative agreement with experiments than those obtained with hard-core spheres. Moreover, once parametrized, the CESP model is also able to quantitatively predict D-long and the anomalous exponent (alpha) for streptavidin diffusion among D10, D400 and D700 dextran obstacles. D-long, the short-time diffusion coefficient (D-short) and alpha are obtained from the BD simulations by using a new empirical expression, able to describe the full temporal evolution of the diffusion coefficient.

• 出版日期2018-4-28