Determination of Polypeptide Backbone Dihedral Angles in Solid State NMR by Double Quantum 13C Chemical Shift Anisotropy Measurements
Authors: Blanco, F.J.; Tycko, R.
Source: Journal of Magnetic Resonance, Volume 149, Number 1, March 2001 , pp. 131-138(8)
Publisher: Academic Press
Abstract:A solid state NMR technique for the determination of peptide backbone conformations at specific sites in unoriented samples under magic angle spinning (MAS) is described and demonstrated on a doubly labeled polycrystalline sample of the tripeptide AlaGlyGly and a sextuply labeled lyophilized sample of the 17-residue peptide MB(i+4)EK. The technique is applicable to peptides and proteins that are labeled with 13C at two (or more) consecutive backbone carbonyl sites. Double quantum (DQ) coherences are excited with a radiofrequency-driven recoupling sequence and evolve during a constant-time t1 period at the sum of the two anisotropic chemical shifts. The relative orientation of the two chemical shift anisotropy (CSA) tensors, which depends on the φ and backbone dihedral angles, determines the t1-dependence of spinning sideband intensities in the DQ-filtered 13C MAS spectrum. Experiments and simulations show that both dihedral angles can be extracted from a single data set. This technique, called DQCSA spectroscopy, may be especially useful when analyzing the backbone conformation of a polypeptide at a particular doubly labeled site in the presence of additional labeled carbons along the sequence.
Document Type: Editorial
Affiliations: Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, 20892-0520
Publication date: 2001-03-01