Three dimensional structure determination for single crystal and uniaxially aligned amino acids by magic angle spinning solid-state NMR.

摘要

Rotational Echo DOuble Resonance (REDOR) and Lee-Goldburg Cross Polarization (LGCP) based experiments are applied for determination of the complete three-dimensional geometries of heteronuclear bond vectors in uniformly aligned samples. While both REDOR and LGCP experiments have been used in the past to measure internuclear distances, the orientational dependence of the heteronuclear coupling values, measured by both REDOR and LGCP (for 13C-15N and 13C-1H respectively), were analyzed to determine the polar and azimuthal angle of the CalphaN and Calpha H bond vectors in a single crystal sample of L-Alanine. The ability to measure the polar angle and relative azimuthal angle of the Calpha H and CalphaN bond vectors in a uniaxially aligned sample of L-alanine was also demonstrated. These measurements were verified by X-ray indexing of the single crystal sample, and closely agree with the literature X-ray and neutron diffraction data.;These MAS NMR experiments show the potential utility of such measurements for complete structure determination of single crystal or uniaxially aligned samples of biological macromolecules.