CONFORMATIONAL DYNAMICS OF PROLINE RESIDUES IN ANTAMANIDE - J-COUPLING ANALYSIS OF STRONGLY COUPLED SPIN SYSTEMS BASED ON E-COSY SPECTRA

The conformational dynamics and individual conformations of the four proline residues in the cyclic decapeptide antamanide in solution are determined from vicinal proton coupling constants combined with the measurement of carbon-13 relaxation times. The coupling constants, obtained by a least-squares analysis of a two-dimensional ECOSY spectrum, are interpreted in terms of generalized Karplus equations. It is found that Pro3 and Pro8 are conformationally rigid, while Pro2 and Pro7 are mobile with a significant population of a second conformation. The time constants that govern the conformational dynamics of the proline residues are estimated to be between 30 and 40 ps. © 1990, American Chemical Society. All rights reserved.