title: Interplay of intra- and intermolecular H-bonding in a progressively solvated macrocyclic peptide.
abstract: Studying solvation of a large molecule on an atomic level is challenging because of the transient character and inhomogeneity of hydrogen bonding in liquid water. We studied water clusters of a protonated macrocyclic decapeptide, gramicidin S, which were prepared in the gas phase and then cooled to cryogenic temperatures. The experiment spectroscopically tracked fine structural changes of the clusters upon increasing the number of attached water molecules from 1 to 50 and distinguished vibrational fingerprints of different conformers. The data indicate that only the first two water molecules induce a substantial change of the gramicidin S structure by breaking two intramolecular noncovalent bonds. The peptide structure remains largely intact upon further solvation, reflecting the interplay between the strong intramolecular and weaker intermolecular hydrogen bonds.
authors.affiliation: Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
authors.forename: Natalia S
authors.initials: NS
authors.lastname: Nagornova
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Rizzo
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Boyarkin
mesh_terms: D001665:Binding Sites; D055598:Chemical Phenomena; D006096:Gramicidin / Q000737:chemistry*; D006860:Hydrogen Bonding; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D012995:Solubility; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D006096:Gramicidin