Two-dimensional NMR studies of [Pro-10] atrial natriuretic factor [7-23

The conformational properties of an analog of atrial naturiuretic factor, [Pro-10] ANF(7-23), were examined in H₂O, H₂O/DMSO-d₆ (2/1), and DMSO-d₆ using two-dimensional nmr techniques. The sequence differs from the native peptide by the absence of the exocyclic N- and C-terminal residues, and the substitution of a proline for a glycine at position 10—a modification expected to reduce the conformational flexibility of this analog. The backbone proton nmr resonances were assigned from two-dimensional correlated spectroscopy (2D-COSY), relayed COSY, and 2D nuclear Overhàuser enhancement (NOE) experiments, and the solution conformation was evaluated from vicinal spin–spin coupling constants and NOE data. Despite the substitution of a proline in the sequence, [Pro-10] ANF(7-23) exhibits a considerable amount of flexibility in all of the solvents employed.