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Inherent Conformational Preferences of Ac‐Gln‐Gln‐NHBn: Sidechain Hydrogen Bonding Supports a β‐Turn in the Gas Phase
Author(s) -
Walsh Patrick S.,
Blodgett Karl N.,
McBurney Carl,
Gellman Samuel H.,
Zwier Timothy S.
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201607842
Subject(s) - chemistry , hydrogen bond , turn (biochemistry) , conformational isomerism , amide , ring (chemistry) , peptide bond , crystallography , gas phase , stereochemistry , residue (chemistry) , side chain , peptide , molecule , organic chemistry , biochemistry , polymer
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.