Structure and water dynamics of aqueous peptide solutions in the presence of co-solvents.
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.
Malardier-Jugroot
Cecile
C
Department of Chemistry and Chemical Engineering, Royal Military College of Canada, Kingston, Canada K7K 7B4.
Bowron
Daniel T
DT
Soper
Alan K
AK
Johnson
Margaret E
ME
Head-Gordon
Teresa
T
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*
C492360:N-acetyl-leucine-methylamide; D012997:Solvents; D014867:Water; D007930:Leucine; D005990:Glycerol; D004121:Dimethyl Sulfoxide