Measurement of internuclear distances in polycrystalline solids. Rotationally enhanced transfer of nuclear spin magnetization

A magic angle spinning (MAS) NMR technique for measurement of the distance between two homonuclear sites separated by as much as 0.5 nm is demonstrated. This is achieved by proton decoupling during the magnetization exchange process, greatly attenuating the influence of abundant nuclear spins, selective isotopic labeling of both sites of interest, so that the system may be approximated as a set of magnetically dilute coupled spin pairs, and MAS with matching of the rotational resonance condition. Tyrosine ethyl ester (TEE), carbon 13 labeled at both the -CH{sub 2}- of the ester moiety and at the 4{prime}-OH aromatic carbon is used as a demonstration of the technique. Calculated data is compared to experimental data.