Monte Carlo simulation studies of neurofilament brushes

We have studied the intermolecular interaction between neurofilaments (NFs) using Monte Carlo simulation methods. NFs are assembled from three distinct molecular weight proteins (NF-L, NF-M, NF-H) that are bound to each other laterally forming 10 nm diameter Þlamentous rods along with side-arm extensions. The molecular model consists of two neuroÞlament backbones along with sidearm extensions that are distributed according to the stoichiometry of the three subunits. The side arms are modeled at amino acid resolution with each amino acid represented by a hard sphere along with the corresponding charge valence. In our previous studies of a single NF brush, we have found that NF-M is most responsible for the neurofilament protrusion. In this study, we discuss the structural properties such as density profiles and mean-square radius of gyration of each type of side arms as a function of the inter-filament distance. Unlike conventional belief that crossbridging by NF-H side chains between the neurofilaments would be formed, we have only found repulsive interaction between the two neurofilaments.