IMPROVED METHOD FOR THE STEREOSPECIFIC H-1-NMR ASSIGNMENTS IN COLLAGEN-LIKE TRIPLE-HELICES

An improved model-based method for the stereospecific assignment of pr ochiral centers in collagen-like triple-helical molecules is introduce d, Using the concepts of reporter atoms and of ensemble NOEs, the prop osed methodology extracts the stereochemical information contained in the chiral elements of triple-helices and transfers it to prochiral ce nters with nondegenerate proton resonances. The improved approach has been successfully validated using -(Gly-Pro-Hyp)(n)-triple-helices for which the stereospecific assignment was previously obtained with esta blished techniques, We have applied our stereochemical characterizatio n to novel peptoid containing triple-helices for which existing method s of stereospecific assignment can not be used for all the prochiral c enters. In our approach, several different NOE measurements are employ ed to make a given stereospecific assignment. The multiple NOE compari sons allow internal cross checks, which reduce the chance of erroneous assignments caused by experimental artifacts including spin diffusion and bias from anisotropic rotational motions. In addition, the multip le NOE comparisons are useful in overcoming problems associated with r esonance overlap often encountered in the H-1-NMR spectra of collagenl ike molecules. Our stereochemical analysis is anticipated to improve t he precision and accuracy of the characterization of collagen-like tri ple-helices through a better correlation of structures with their H-1- NMR spectra. (C) 1998 Wiley-Liss, Inc.