Revised CHARMM force field parameters for iron-containing cofactors of photosystem II

Photosystem II is a complex protein-cofactor machinery that splits water molecules into molecular oxygen, protons, and electrons. All-atom molecular dynamics simulations have the potential to contribute to our general understanding of how photosystem II works. To perform reliable all-atom simulations, we need accurate force field parameters for the cofactor molecules. We present here CHARMM bonded and non-bonded parameters for the iron-containing cofactors of photosystem II that include a six-coordinated heme moiety coordinated by two histidine groups, and a non-heme iron complex coordinated by bicarbonate and four histidines. The force field parameters presented here give water interaction energies and geometries in good agreement with the quantum mechanical target data. (c) 2017 Wiley Periodicals, Inc.