title: Charge transfer in model peptides: obtaining Marcus parameters from molecular simulation.
abstract: Charge transfer within and between biomolecules remains a highly active field of biophysics. Due to the complexities of real systems, model compounds are a useful alternative to study the mechanistic fundamentals of charge transfer. In recent years, such model experiments have been underpinned by molecular simulation methods as well. In this work, we study electron hole transfer in helical model peptides by means of molecular dynamics simulations. A theoretical framework to extract Marcus parameters of charge transfer from simulations is presented. We find that the peptides form stable helical structures with sequence dependent small deviations from ideal PPII helices. We identify direct exposure of charged side chains to solvent as a cause of high reorganization energies, significantly larger than typical for electron transfer in proteins. This, together with small direct couplings, makes long-range superexchange electron transport in this system very slow. In good agreement with experiment, direct transfer between the terminal amino acid side chains can be dicounted in favor of a two-step hopping process if appropriate bridging groups exist.
authors.affiliation: Department for Theoretical Chemical Biology, Institute for Physical Chemistry, Karlsruhe Institute of Technology, Kaiserstr. 12, 76131 Karlsruhe, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Heck
authors.forename: P Benjamin
authors.initials: PB
authors.lastname: Woiczikowski
authors.forename: Tomáš
authors.initials: T
authors.lastname: Kubař
authors.forename: Bernd
authors.initials: B
authors.lastname: Giese
authors.forename: Marcus
authors.initials: M
authors.lastname: Elstner
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Steinbrecher
mesh_terms: D004583:Electrons; D056004:Molecular Dynamics Simulation; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D055672:Static Electricity
chemical_list: D010455:Peptides