title: β-Sheet 13C structuring shifts appear only at the H-bonded sites of hairpins.
abstract: The (13)C chemical shifts measured for designed β-hairpins indicate that the structuring shifts (upfield for Cα and C', downfield for Cβ) previously reported as diagnostic for β-structuring in proteins appear only at the H-bonded strand residues. The resulting periodicity of structuring shift magnitudes is not, however, a consequence of H-bonding status; rather, it reflects a previously unrecognized alternation in the backbone torsion angles of β-strands. This feature of hairpins is also likely to be present in proteins. The study provides reference values for the expectation shifts for (13)C sites in β-structures that should prove useful in the characterization of the folding equilibria of β-sheet models.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
authors.forename: Irene
authors.initials: I
authors.lastname: Shu
authors.forename: James M
authors.initials: JM
authors.lastname: Stewart
authors.forename: Michele
authors.initials: M
authors.lastname: Scian
authors.forename: Brandon L
authors.initials: BL
authors.lastname: Kier
authors.forename: Niels H
authors.initials: NH
authors.lastname: Andersen
mesh_terms: D006860:Hydrogen Bonding; D019906:Nuclear Magnetic Resonance, Biomolecular; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
chemical_list: D011506:Proteins