Solid-State NMR Determination of Peptide Torsion Angles:  Applications of 2H-Dephased REDOR

• Published in: Journal of the American Chemical Society 2000-12, Vol.122 (49), p.12263-12269
• Main Authors: Sack, Ingolf, Balazs, Yael S, Rahimipour, Shai, Vega, Shimon
• Format: Article
• Language: eng ; jpn
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja000489w

The backbone conformation of peptides and proteins is completely defined by the torsion angles (φ,ψ,ω) of each amino acid residue along the polypeptide chain. We demonstrate a solid-state NMR method based on heteronuclear distance measurements for determining (φ,ψ) angles. Simple and reliable deuterium phase modulated pulses (PM5) reintroduce dipolar couplings between 2H and a spin-1/2 nucleus. Measuring the 13C i- 1{2H i α} REDOR distance across a peptide bond results in the torsion angle φ i as a consequence of the restricted geometry of the peptide backbone. The 15N i+ 1{2H i α} REDOR distance across a peptide bond defines the torsion angle ψ i . This approach is demonstrated for both the 3-spin X{2H2}REDOR case of glycine and the 2-spin X{2H}REDOR case, represented by l-alanine, using two different tripeptides. It is shown that the technique can handle multiple sample conformations. PM5-REDOR decay curves of the ψ angle show distinctly different behaviors between α-helix and β-sheet backbone conformations.