Polymer brushes: from physics to biology

" Biological brush-like structures found in nature are charged, and electrostatic interactions are believed to play important role in these systems. We first consider planar brushes of tethered polyelectrolytes (PEs) in contact with solution of monovalent salt. A classical scaling model assumes Gaussian elasticity of tethered chains and provides asymptotic power law dependences for averaged brush thickness and free energy as a function of molecular weight of the chains, grafting density and solution salinity. We demonstrate that elasticity of polyions is modified by intermolecular repulsions between charges. As a result, scaling exponent in salt dependence of PE brush thickness is changed. The response of PE brush to compression by impermeable surface is governed by increased pressure of counterions, and the force-distance profile is not essentially affected by modified polyion elasticity.


A more refined numerical self-consistent field (SCF) model is applied to study the structure of biological brush � the corona formed by projection domains of triplet (NF-L, NF-M and NF-H) proteins around the core of neurofilament (NF). NFs are major constituents of cytoskeleton in neuronal cells that provide mechanical strength to axons. We analyze theoretically (i) the equilibrium structure and average thickness of NF brush as a function of NF protein ratio and level of phosphorylation (degree of charging) of the projection domains and (ii) response of NF brush to compression. The theoretical predictions are compared to experimental data for both invivo and invitro systems."