Determination of molecular geometry by high-order multiple-quantum evolution in solid-state NMR.
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.
Edén
M
M
Physical Chemistry Division, Stockholm University, Stockholm, S-106 91, Sweden. mhl@physc.su.se
Brinkmann
A
A
Luthman
H
H
Eriksson
L
L
Levitt
M H
MH
D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008962:Models, Theoretical; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D013113:Spin Labels
D010455:Peptides; D013113:Spin Labels