Two‐dimensional 1 H‐nmr study of synthetic peptides containing the main immunogenic region of the Torpedo acetylcholine receptor

A comparative 1 H‐NMR spectral study of a synthetic decapeptide containing the main immunogenic region of the Torpedo acetylcholine receptor (AChR; WNPADYGGIK, representing the α67–76 fragment of Torpedo AChR) with four analogous peptides (WNP 3 ‐D 5 YGGIK, WNPAA 5 YGGIK, WNPADYGGA 9 K, and WNPD 4 DYGGV 9 K) has been carried out in dimethyl sulfoxide. One‐ and two‐dimensional nmr experiments [correlated spectroscopy (COSY), relayed COSY, and phase‐sensitive nuclear Overhauser enhancement spectroscopy (NOESY)] were performed to obtain complete assignments of the proton resonances. The presence of strong and multiple short‐ and long‐range NOEs, and especially a strong long‐range NOE between the two Asn 2 ‐CαH and Gly 7 ‐CαH protons, argues in favor of a rigid folded structure in all five cases. Temperature dependence measurements indicate the existence of three intramolecular interactions involving the Asp 3 , Gly 8 , and Lys 10 amide protons.