title: Compact folding of isolated four-residue neutral peptide chains: H-bonding patterns and entropy effects.
abstract: The intrinsic folding of isolated neutral tetrapeptides is investigated by IR-UV double-resonance laser spectroscopy coupled to quantum chemistry (DFT-D) calculations. Laser-desorbed jet-cooled Ac-(Ala)(3)-Phe-NH(2) as well as two other related four-residue molecules are shown to fold according to the same 14-7L-X-10II'-7L compact, β-hairpin-like backbone pattern, leading to a remarkable closed daisy chain of H-bonds along the molecule. Thermodynamic calculations confronted to the abundances observed show that these laser-desorbed peptides are best described by a finite conformational temperature (typically ca. 300-450 K), which suggests that not only enthalpy but also entropy effects play an important role in selecting these structures within this temperature range.
authors.affiliation: CEA Saclay, DSM, IRAMIS, Service des Photons, Atomes et Molécules and CNRS, Laboratoire Francis Perrin, URA CNRS 2453, Bât 522, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Plowright
authors.forename: Eric
authors.initials: E
authors.lastname: Gloaguen
authors.forename: Michel
authors.initials: M
authors.lastname: Mons
mesh_terms: D006860:Hydrogen Bonding; D007834:Lasers; D010455:Peptides / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013816:Thermodynamics
chemical_list: D010455:Peptides