Two-dimensional 1H NMR studies of rat atrial natriuretic factor(1-23)

Using a variety of two-dimensional NMR methods, the 1H NMR resonances of rat ANF(1-23) in dimethyl sulfoxide-d6 solution have been assigned. Two-dimensional phase sensitive correlated spectroscopy was used to identify protons that are scalar coupled and were also used to obtain coupling constants (3JNH-alpha CH) in complicated regions of the spectra. Relayed coherence transfer experiments proved useful in identifying the connectivities between the NH and beta-protons of the same amino acid residue. Finally, phase sensitive 2D NOE experiments allowed the identification of protons close in space between adjacent residues, thus providing the sequential assignments as well as conformational information. These preliminary results (chemical shifts, coupling constants, NOEs) were analyzed in terms of possible polypeptide secondary structures and were found to be consistent with a beta-type structure or an averaging of solution conformations (random coil).