title: Determination of molecular geometry by high-order multiple-quantum evolution in solid-state NMR.
abstract: The principles of molecular geometry determination by high-quantum heteronuclear local field spectroscopy in solid-state NMR are discussed. The extreme multiple-quantum coherences in a cluster of nuclear spins are allowed to evolve in the presence of heteronuclear through-space couplings to two spins of a different type. The multiple-quantum dephasing curve is independent of the homonuclear spin-spin couplings and may be described in terms of geometric parameters. The triple-quantum version of the experiment is demonstrated by determining the psi torsion angle in a [(15)N(2), (13)C(3)]-labeled sample of the peptide ala-ala-gly. Two regions of torsion angle space fit the experimental data, one in the neighborhood of -152 degrees and one in the neighborhood of +161 degrees. The latter determination is in excellent agreement with the X-ray estimate of +160.5 degrees.
authors.affiliation: Physical Chemistry Division, Stockholm University, Stockholm, S-106 91, Sweden. mhl@physc.su.se
authors.forename: M
authors.initials: M
authors.lastname: Edén
authors.forename: A
authors.initials: A
authors.lastname: Brinkmann
authors.forename: H
authors.initials: H
authors.lastname: Luthman
authors.forename: L
authors.initials: L
authors.lastname: Eriksson
authors.forename: M H
authors.initials: MH
authors.lastname: Levitt
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008962:Models, Theoretical; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D013113:Spin Labels
chemical_list: D010455:Peptides; D013113:Spin Labels