title: Ultrafast Reorientational Dynamics of Leucine at the Air-Water Interface.
abstract: Ultrafast dynamics of protein side chains are involved in important biological processes such as ligand binding, protein folding, and hydration. In addition, the dynamics of a side chain can report on local environments within proteins. While protein side chain dynamics have been probed for proteins in solution with nuclear magnetic resonance and infrared methods for decades, information about side chain dynamics at interfaces is lacking. At the same time, the dynamics and motions of side chains can be particularly important for interfacial binding and protein-driven surface manipulation. We here demonstrate that ultrafast reorientation dynamics of leucine amino acids at interfaces can be recorded in situ and in real time using polarization- and time-resolved pump-probe sum frequency generation (SFG). Combined with molecular dynamics simulations, time-resolved SFG was used to probe the reorientation of the isopropyl methyl groups of l-leucine at the air-water interface. The data show that the methyl units reorient diffusively at an in plane rate of Dφ = 0.07 rad(2)/ps and an out of plane rate of Dθ = 0.05 rad(2)/ps.
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Donovan
authors.affiliation: Department of Chemical Engineering, University of Washington , 105 Benson Hall, Seattle, Washington 98195-1750, United States.
authors.forename: Yeneneh Y
authors.initials: YY
authors.lastname: Yimer
authors.affiliation: Department of Chemical Engineering, University of Washington , 105 Benson Hall, Seattle, Washington 98195-1750, United States.
authors.forename: Jim
authors.initials: J
authors.lastname: Pfaendtner
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Ellen H G
authors.initials: EH
authors.lastname: Backus
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Mischa
authors.initials: M
authors.lastname: Bonn
authors.affiliation: Max Planck Institute for Polymer Research , Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Weidner
mesh_terms: D000388:Air; D007930:Leucine / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D011506:Proteins / Q000737:chemistry*; D014732:Vibration; D014867:Water / Q000737:chemistry
chemical_list: D011506:Proteins; D014867:Water; D007930:Leucine