Many-body van der Waals forces, polarization response and dynamical effects in poly-peptides

The modeling of conformations and dynamics of supramolecular systems is of primary importance for understanding physicochemical properties of soft matter. Although short-range interactions such as covalent and hydrogen bonding control the local molecular arrangements, non-covalent interactions play a dominant role in determining the global character of the conformations. The many-body dispersion (MBD) approach enables the inclusion of non-pairwise contributions that consistently yield more accurate energies and longer ranged forces than standard Lennard-Jones-like potentials. Here we focus on the signatures of such many-body forces on the dynamical properties of small peptides, both in terms of simplified backbone models and for a 15-residue polyalanine within semiempirical quantum mechanics. We show that beyond-pairwise terms consistently yield a decreased roughness of the energy landscape and more compact, globally optimized conformations [arXiv:2110.06646]. This is intimately related to the delocalization of the force contributions that derives from the higher versatility of the polarization response tensor. We therefore focus our analysis on such response properties, discussing coarse-graining strategies towards the formulation of MBD polarizabilities in terms of fragments, rather than atoms.