INTERNUCLEAR DISTANCE MEASUREMENTS UP TO 0.44 NM FOR RETINALS IN THE SOLID-STATE WITH 1-D ROTATIONAL RESONANCE C-13 MAS NMR-SPECTROSCOPY

The results presented in this paper show that accurate through-space i nternuclear distance measurements can be performed on doubly labeled r etinals using the one-dimensional approach to the solid state magic an gle spinning (MAS) rotational resonance NMR technique. The apparent sp litting Delta omega(1) of the resonances at n = 1 rotational resonance for the labeled vinylic positions of (all-E)-[10,20-C-13(2)]retinal, (all-E)-[11,20-C-13(2)]retinal, and (all-E)-[12,20-C-13(2)]retinal can be simulated with a coherent set of parameters. From a series of simu lations with different dipolar coupling constant brs, it appears that b(IS)/2 pi root 8 = 1.15(Delta omega(1)/2 pi) + 7 (Hz) to a good appro ximation. Using this relationship as a calibration, it is demonstrated with a set of model compounds that straightforward Lorentzian fitting to measure Delta omega(1) can be used to determine internuclear dista nces up to 0.44 nm in doubly labeled retinals in the solid state.