Solution conformation of a synthetic fragment of human pituitary growth hormone. Two-dimensional NMR of an alpha-helical dimer.

Circular dichroism and two-dimensional NMR spectra indicate that a peptide fragment consisting of the first 28 residues from the N-terminus of human growth hormone (hGH 1-28) has considerable alpha-helical structure. The peptide, (1) H-Phe-Pro-Thr-Ile-Pro-Leu-Ser-Arg-Leu-Phe-Asp-Asn-Ala-Met-Leu-Arg-Ala-Hi s-Arg- Leu-His-Gln-Leu-Ala-Phe-Asp-Thr-Tyr-OH (28), was synthesized on an automated peptide synthesizer using the Merrifield solid-phase method. The peptide can be modeled as an amphiphilic helix, and the unusual stability of the alpha-helix in aqueous solution is suggested to be attributable to formation of a dimer of alpha-helices.