Coarse-grained model of nucleic acid bases

Atomistic simulations of nucleic acids are prohibitively expensive and, consequently, reduced models of these compounds are of great interest in the field. In this work, we propose a physics-based coarse-grained model of nucleic-acid bases in which each base is represented by several (3-5) interaction centers. van der Waals interactions are modeled by Lennard-Jones spheres with a 12-6 potential energy function. The charge distribution is modeled by a set of electric dipole moments located at the centers of the Lennard-Jones spheres. The method for computing the Lennard-Jones parameters, electric dipole moments (their magnitude and orientation) and positions of the interaction centers is described. Several models with different numbers of interaction centers were tested. The model with three-center cytosine, four-center guanine, four-center thymine, and five-center adenine satisfactorily reproduces the canonical Watson-Crick hydrogen bonding and stacking interaction energies of the all-atom AMBER model. The computation time with the coarse-grained model is reduced seven times compared with that of the all-atom model.