EGF is a 53 residue polypeptide of multiple biological activities. Homonuclear decoupling, spin-echo multiplet selection and Photo-CIDNP experiments lead us to fully assign the resonances from the aromatic side chains (5 Tyr, 1 His and 2 Trp). The photochemical experiment gives specific attribution of doublets in tyrosines and multiplets in tryptophans. The resonances from two tyrosines are broadened and shifted at high fields, suggesting the existence of hydrophobic domains in EGF, consistent with the presence of ring current shifted methyl resonances. However, the amide exchange in D2O solution is considerably faster than that observed for globular proteins of the same size, and most of the aromatic residues are accessible to the flavin dye. The combined evidence suggests that EGF possesses a folded structure, but the molecule is rather floppy. From spectra measured at variable temperature a ΔG° at 25°C of about 8 kcal/mol is calculated.
