Two-dimensional1H-nmr investigation of the water conformation of the atrial natriuretic factor (ANF 101-126)

The complete sequential assignment of the 1 H‐nmr resonance frequencies of the active fragment of the rat atrial natriuretic factor (ANF 101–126) has been performed. Two‐dimensional nmr techniques have been employed, including phase‐sensitive nuclear Overhauser spectroscopy (NOESY), relayed coherence transfer spectroscopy (RELAY), and J ‐correlated spectroscopy (COSY). Experiments were performed both in D 2 0 and H 2 0 solutions at different pH values. With few exceptions, resonance frequencies were practically pH independent. NOESY spectra were recorded using both 300‐ and 500‐ms mixing times, and no long‐range connectivities were observed, leading to the conclusion that ANF 101–126 has no defined secondary nor tertiary structure in water in the pH range used (2.73–5.21).