Carbon‐13 NMR chemical shifts of the common amino acid residues measured in aqueous solutions of the linear tetrapeptides H‐Gly‐Gly‐ X‐L‐ Ala‐OH

Abstract The 13 C nmr chemical shifts of the common amino acid residues were measured in D 2 O solutions of the linear tetrapeptides H‐Gly‐Gly‐X‐ L ‐Ala‐OH. For Asp, Glu, Lys, Tyr and His, the titration shifts arising from the ionization of te amino acid side chains were also obtained. These data are compared with the corresponding 13 C chemical shifts in the protected tetrapeptides CF 3 CO‐Gly‐Gly‐X‐ L ‐Ala‐OCH 3 , the linear pentapeptides H‐Gly‐Gly‐X‐Gly‐Gly‐OH, and the free amino acids. On this basism the selection of suitable “random coil” 13 C chemical shifts for conformational studies of polypeptides chain is discussed.