Measurement of Internuclear Distances in Solids Using Variations of Rotational-Echo Double-Resonance NMR.

Rotational-echo, double-resonance (REDOR) nuclear magnetic resonance (NMR) has been used to measure internuclear distances in solids in many isotopically labeled biological solids. The goals of my research have been to adapt this technique to make it suitable for some special systems, such as samples with low isotopic label concentrations, samples with NMR resonances that have large chemical shift anisotropies, non-biological samples with high NMR-active spin concentrations but no isotopic spin labels, and samples having interactions between a nuclear spin and an electron. This work has included the development of multiple-resonance, background suppression techniques, such as double REDOR, rotational-echo, triple-resonance (RETRO) and transferred -echo, double-resonance (TEDOR), to be used in conjunction with REDOR on labeled biological solids. These methods have enabled the determination of a ^{13 }C-^{15}N one-bond distance of 1.48 A in glyphosate by double REDOR, and a ^{13}C- ^{19}F internuclear distance of 8.0 A in emerimicin using TEDOR-REDOR. Semiconductor materials are more difficult to specifically label than biological samples because they are made by solid-state, high-temperature methods. Using REDOR and a simple statistical model, accurate one-bond internuclear distances in cadmium phosphide ranging from 2.55 to 2.58 A were measured. The lattice contractions of crystalline domains in a mixed-phase (part amorphous, part crystalline) sample were measured to be four to five percent using REDOR. The multiple resonance, magic-angle spinning, solid-state NMR techniques described in this dissertation require up to four radiofrequency channels in the same experiment.