Secondary structure of the human growth hormone releasing factor (GRF 1–29) by two‐dimensional 1H‐nmr spectroscopy

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Abstract
The secondary structure of the human growth hormone releasing factor (GRF 1‐29) in a solution mixture of 60% aqueous phosphate buffer:40% 2,2,2‐trifluoroethanol‐d3 has been investigated by two‐dimensional 1H‐nmr spectroscopy. Sequential resonance assignments and elements of secondary structure were obtained from phase‐sensitive correlation spectroscopy, relayed coherence spectroscopy, and nuclear Overhauser spectroscopy experiments. The observation of a large number of α‐amide and amide‐amide interresidual nuclear Overhauser effect connectivities as well as the existence of 11 slowly exchanging amide protons indicates that the peptide adopts a well‐defined secondary structure most likely constituted of a single long helix. This conclusion is consistent with the CD measurements.