Determination of heteronuclear three-bond J-coupling constants in peptides by a simple heteronuclear relayed E.COSY experiment

Summary

A simple heteronuclear relayed E.COSY pulse sequence with a minimum number of pulses is proposed for the quantitative determination of heteronuclear three-bond J-coupling constants in uniformly ¹³C-enriched polypeptide samples. Numerous heteronuclear three-bond coupling constants, including ${}^3{\text{J}}_{{\text{H}}^{\text{N}} {\text{C}}'}$, ${}^3{\text{J}}_{{\text{H}}^{\text{N}} {\text{C}}^\beta }$, ${}^3{\text{J}}_{{\text{H}}^\beta {\text{C}}'}$, and ${}^3{\text{J}}_{{\text{H}}^\alpha {\text{C}}^\gamma }$, can be determined for each residue from a single heteronuclear relayed E.COSY spectrum. Couplings relevant for stereospecific assignments as well as for the determination of dihedral angles in the amino acid backbone and in side chains are obtained. The method is demonstrated on the uniformly ¹³C-enriched decapeptide antamanide (-Val¹-Pro²-Pro³-Ala⁴-Phe⁵-Phe⁶-Pro⁷-Pro⁸-Phe⁹-Phe¹⁰-).