Cory's Comment: CP & symmetry-based recoupling to detect carbon-13 J-couplings.
Title: Accurate Measurements of 13C-13C J-Couplings in the Rhodopsin Chromophore by Double-Quantum Solid-State NMR Spectroscopy
Authors: Lyndon Emsley, Steven P. Brown, Richard C. D. Brown, Willem J. DeGrip, and Malcolm H. Levitt et al...
Page #: 3878
Abstract: A new double-quantum solid-state NMR pulse sequence is presented and used to measure one-bond 13C-13C J-couplings in a set of 13C2-labeled rhodopsin isotopomers. The measured J-couplings reveal a perturbation of the electronic structure at the terminus of the conjugated chain but show no evidence for protein-induced electronic perturbation near the C11-C12 isomerization site. This work establishes NMR methodology for measuring accurate 1JCC values in noncrystalline macromolecules and shows that the measured J-couplings may reveal local electronic perturbations of mechanistic significance.
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