title: Average and extreme multi-atom Van der Waals interactions: strong coupling of multi-atom Van der Waals interactions with covalent bonding.
abstract: BACKGROUND
  The prediction of ligand binding or protein structure requires very accurate force field potentials - even small errors in force field potentials can make a 'wrong' structure (from the billions possible) more stable than the single, 'correct' one. However, despite huge efforts to optimize them, currently-used all-atom force fields are still not able, in a vast majority of cases, even to keep a protein molecule in its native conformation in the course of molecular dynamics simulations or to bring an approximate, homology-based model of protein structure closer to its native conformation.
  
  
  RESULTS
  A strict analysis shows that a specific coupling of multi-atom Van der Waals interactions with covalent bonding can, in extreme cases, increase (or decrease) the interaction energy by about 20-40% at certain angles between the direction of interaction and the covalent bond. It is also shown that on average multi-body effects decrease the total Van der Waals energy in proportion to the square root of the electronic component of dielectric permittivity corresponding to dipole-dipole interactions at small distances, where Van der Waals interactions take place.
  
  
  CONCLUSIONS
  The study shows that currently-ignored multi-atom Van der Waals interactions can, in certain instances, lead to significant energy effects, comparable to those caused by the replacement of atoms (for instance, C by N) in conventional pairwise Van der Waals interactions.
authors: Institute of Protein Research, Russian Academy of Sciences, Pushchino, Moscow Region, Russia. afinkel@vega.protres.ru
authors: Alexei V
authors: AV
authors: Finkelstein