title: Inherent Conformational Preferences of Ac-Gln-Gln-NHBn: Sidechain Hydrogen Bonding Supports a β-Turn in the Gas Phase.
abstract: Gas-phase single-conformation spectroscopy is used to study Ac-Gln-Gln-NHBn in order to probe the interplay between sidechain hydrogen bonding and backbone conformational preferences. This small, amide-rich peptide offers many possibilities for backbone-backbone, sidechain-backbone, and sidechain-sidechain interactions. The major conformer observed experimentally features a type-I β-turn with a canonical 10-membered ring C=O-H-N hydrogen bond between backbone amide groups. In addition, the C=O group of each Gln sidechain participates in a seven-membered ring hydrogen bond with the backbone NH of the same residue. Thus, sidechain hydrogen-bonding potential is satisfied in a manner that is consistent with and stabilizes the β-turn secondary structure. This turn-forming propensity may be relevant to pathogenic amyloid formation by polyglutamine segments in human proteins.
authors: Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
authors: Patrick S
authors: PS
authors: Walsh
authors: Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
authors: Karl N
authors: KN
authors: Blodgett
authors: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors: Carl
authors: C
authors: McBurney
authors: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
authors: Samuel H
authors: SH
authors: Gellman
authors: Department of Chemistry, Purdue University, West Lafayette, IN, 47907, USA.
authors: Timothy S
authors: 0000-0002-4468-5748
authors: TS
authors: Zwier
keywords: IR spectroscopy; density functional calculations; gas-phase chemistry; glutamine; supersonic expansion