title: Effect of viscogens on the kinetic response of a photoperturbed allosteric protein.
abstract: By covalently binding a photoswitchable linker across the binding groove of the PDZ2 domain, a small conformational change can be photo-initiated that mimics the allosteric transition of the protein. The response of its binding groove is investigated with the help of ultrafast pump-probe IR spectroscopy from picoseconds to tens of microseconds. The temperature dependence of that response is compatible with diffusive dynamics on a rugged energy landscape without any prominent energy barrier. Furthermore, the dependence of the kinetics on the concentration of certain viscogens, sucrose, and glycerol, has been investigated. A pronounced viscosity dependence is observed that can be best fit by a power law, i.e., a fractional viscosity dependence. The change of kinetics when comparing sucrose with glycerol as viscogen, however, provides strong evidence that direct interactions of the viscogen molecule with the protein do play a role as well. This conclusion is supported by accompanying molecular dynamics simulations.
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Waldauer
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Stucki-Buchli
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland.
authors.forename: Lukas
authors.initials: L
authors.lastname: Frey
authors.affiliation: Department of Chemistry, University of Zurich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Hamm
mesh_terms: D005990:Glycerol / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008027:Light; D056004:Molecular Dynamics Simulation; D054731:PDZ Domains; D055668:Photochemical Processes; D017510:Protein Folding; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13 / Q000737:chemistry; D013395:Sucrose / Q000737:chemistry; D014783:Viscosity
chemical_list: D013395:Sucrose; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D005990:Glycerol