title: Modeling nonaqueous proton wires built from helical peptides: biased proton transfer driven by helical dipoles.
abstract: We report gas-phase electronic structure calculations on helical peptides that act as scaffolds for imidazole-based hydrogen-bonding networks (proton wires). We have modeled various 21-residue polyalanine peptides substituted at regular intervals with histidines (imidazole-bearing amino acids), using a hybrid approach with a semiempirical method (AM1) for peptide scaffolds and density functional theory (B3LYP) for proton wires. We have computed energy landscapes including barriers for Grotthuss-shuttling-type proton motions though wires supported on 3(10)-, α- and π-helical structures, showing the 3(10)- and α-helices to be attractive targets in terms of high proton affinities, low Grotthuss shuttling barriers, and high stabilities. Moreover, bias forces provided by the helical dipole moments were found to promote unidirectional proton translocation.
authors.affiliation: Department of Chemistry, University of Puerto Rico at Mayagüez, Mayagüez, Puerto Rico 00681. gustavo.lopez@upr.edu
authors.forename: Gustavo E
authors.initials: GE
authors.lastname: López
authors.forename: Inara
authors.initials: I
authors.lastname: Colón-Díaz
authors.forename: Anthony
authors.initials: A
authors.lastname: Cruz
authors.forename: Sumana
authors.initials: S
authors.lastname: Ghosh
authors.forename: Samantha B
authors.initials: SB
authors.lastname: Nicholls
authors.forename: Usha
authors.initials: U
authors.lastname: Viswanathan
authors.forename: Jeanne A
authors.initials: JA
authors.lastname: Hardy
authors.forename: Scott M
authors.initials: SM
authors.lastname: Auerbach
mesh_terms: D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D011522:Protons; D011789:Quantum Theory
chemical_list: D010455:Peptides; D011522:Protons