Stereospecific assignments of side-chain protons and characterization of torsion angles in Eglin c.

Stereospecific assignments were obtained in the protein Eglin c for beta-methylene protons of 9 out of the 24 residues with AMX symmetry, for three residues with long side chains and for the gamma-methyl groups of 8 out of the 11 valines. This was achieved by analyzing the cross-peak multiplet structures in two-dimensional correlated spectra with spectral simulations and peak fitting, and by quantitative measurements of intraresidue nuclear Overhauser enhancements. In addition to the stereospecific assignments, information on the torsion angles phi and chi 1 was obtained. To estimate inferences of internal motions on this analysis, the effect of uniform averaging within a certain range of the torsion angle chi 1 on cross-peak multiplet structures and on relative intraresidue nuclear Overhauser enhancement is discussed.