Two- and Three-Dimensional 1H/13C PISEMA Experiments and Their Application to Backbone and Side Chain Sites of Amino Acids and Peptides

Abstract

Two-dimensional 1H/13C polarization inversion spin exchange at the magic angle experiments were applied to single crystal samples of amino acids to demonstrate their potential utility on oriented samples of peptides and proteins. High resolution is achieved and structural information obtained on backbone and side chain sites from these spectra. A triple-resonance experiment that correlates the 1H-13Cα dipolar coupling frequency with the chemical shift frequencies of the α-carbon, as well as the directly bonded amide 15N site, is also demonstrated. In this experiment the large 1H-13Cα heteronuclear dipolar interaction provides an independent frequency dimension that significantly improves the resolution among overlapping 13C resonances of oriented polypeptides, while simultaneously providing measurements of the 13Cα chemical shift, 1H-13C dipolar coupling, and 15N chemical shift frequencies and angular restraints for backbone structure determination. © 1999 Academic Press.