title: Structure and water dynamics of aqueous peptide solutions in the presence of co-solvents.
abstract: We perform neutron diffraction and quasi-elastic neutron scattering (QENS) to probe hydration water structure, and dynamics down to supercooled temperatures, of a concentrated amphiphilic peptide system with the co-solvents glycerol and dimethyl sulfoxide. We find that the kosmotropic co-solvent glycerol preserves the hydration structure near the peptide that is observed in the water solvent alone, that in turn preserves the dynamical temperature trends of two water relaxation processes--one corresponding to a localized relaxation process of the peptide bound surface water and a second relaxation process of the outer hydration layers. By contrast the chaotropic co-solvent, by disrupting the hydration layer near the peptide surface, eliminates the inner hydration layer relaxation process induced by the peptide, to show a single time scale for translational water dynamics.
authors.affiliation: Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, Canada K7K 7B4.
authors.forename: Cecile
authors.initials: C
authors.lastname: Malardier-Jugroot
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Bowron
authors.forename: Alan K
authors.initials: AK
authors.lastname: Soper
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Johnson
authors.forename: Teresa
authors.initials: T
authors.lastname: Head-Gordon
mesh_terms: D004121:Dimethyl Sulfoxide / Q000737:chemistry; D005990:Glycerol / Q000737:chemistry; D007930:Leucine / Q000031:analogs & derivatives* / Q000737:chemistry; D033363:Neutron Diffraction; D012997:Solvents / Q000737:chemistry*; D013696:Temperature; D014867:Water / Q000737:chemistry*
chemical_list: C492360:N-acetyl-leucine-methylamide; D012997:Solvents; D014867:Water; D007930:Leucine; D005990:Glycerol; D004121:Dimethyl Sulfoxide