title: 13C NMR reveals no evidence of n-π* interactions in proteins.
abstract: An n = π* interaction between neighboring carbonyl groups has been postulated to stabilize protein structures. Such an interaction would affect the (13)C chemical shielding of the carbonyl groups, whose paramagnetic component is dominated by n = π* and π = π* excitations. Model compound calculations indicate that both the interaction energetics and the chemical shielding of the carbonyl group are instead dominated by a classical dipole-dipole interaction. A set of high-resolution protein structures with associated carbonyl (13)C chemical shift assignments verifies this correlation and provides no evidence for an inter-carbonyl n = π* interaction.
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America.
authors.forename: Bradley
authors.initials: B
authors.lastname: Worley
authors.forename: Georgia
authors.initials: G
authors.lastname: Richard
authors.forename: Gerard S
authors.initials: GS
authors.lastname: Harbison
authors.forename: Robert
authors.initials: R
authors.lastname: Powers
mesh_terms: D002247:Carbon Isotopes; D006860:Hydrogen Bonding; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D011506:Proteins / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D011506:Proteins