Molecular dynamics of a FUS droplet wetting an actin filament*

Liquid phase-separating proteins are an active area of investigation in soft material design and the study of biomolecular condensates. Recent studies include the FUS protein, a naturally occurring biopolymer that wets actin filaments and bundles them into networks. However, such cellular biochemistry is sensitive to energetic and entropic forces and the mechanisms of wetting are not fully understood at the nanoscale level. We preset molecular dynamics simulations of FUS droplets forming from protein suspensions and of a FUS droplet spreading on an infinite actin filament. We used a modified Martini coarse grained force-field for protein-protein interactions as described in the literature [Benayad et al. (2021), J. Chem. Theory Comput. 17, 525-537] and extended it to FUS-actin interactions. We analyze the structural and energetic phenomena of liquid phase separating protein droplets in time and space. Thermodynamic and energetic properties such as surface tension, droplet-filament contact angles, spreading parameter, and cohesive and interaction energies are reported.