title: Solvation dynamics of model peptides probed by terahertz spectroscopy. Observation of the onset of collective network motions.
abstract: We have studied the solvation of model peptides at low hydration levels by terahertz absorption spectroscopy. We have recorded the concentration-dependent terahertz absorption coefficients of N-acetyl-glycine-amide (NAGA), N-acetyl-glycine-methylamide (NAGMA), N-acetyl-leucine-amide (NALA), N-acetyl-leucine-methylamide (NALMA), and N-acetyl-tryptophan-amide (NATA) in aqueous solution. We find a dramatic decrease in the THz absorption, if the number of water molecules per solute is less than 18-20. This change is taken as a signature for the breakdown of peptide-water network motions, which supports the hypothesis that a minimum number of hydration waters is required to activate these motions. This is well below a monolayer coverage of the model peptides. It is interesting to note that the required hydration level corresponds to the number of water molecules which are required for biological functionality.
authors.affiliation: Lehrstuhl für Physikalische Chemie 2, Ruhr-Universität Bochum, 44780 Bochum, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Born
authors.forename: Hermann
authors.initials: H
authors.lastname: Weingärtner
authors.forename: Erik
authors.initials: E
authors.lastname: Bründermann
authors.forename: Martina
authors.initials: M
authors.lastname: Havenith
mesh_terms: D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D010455:Peptides