Symmetry-based constant-time homonuclear dipolar recoupling in solid state NMR.

摘要: Constant-time dipolar recoupling pulse sequences are advantageous in structural studies by solid state nuclear magnetic resonance (NMR) with magic-angle spinning (MAS) because they yield experimental data that relatively insensitive to radio-frequency imperfections and spin relaxation processes. A new approach the construction of constant-time homonuclear is described, based on symmetry properties recoupled dipole-dipole interaction Hamiltonian under cyclic displacements time respect MAS sample rotation period. specific symmetry-based sequence called PITHIRDS-CT introduced demonstrated experimentally. (13)C NMR for singly-(13)C-labeled amino acid powders amyloid fibrils indicate effectiveness measurements intermolecular distances solids. (15)N-detected (13)C-detected intramolecular (15)N-(15)N peptides alpha-helical beta-sheet structures utility molecular conformations, especially backbone psi torsion angles containing uniformly (15)N- (13)C-labeled acids.