3D 13C-15N-heteronuclear two-spin coherence spectroscopy for polypeptide backbone assignments in 13C-15N-double-labeled proteins

Abstract
Summary The pulse sequence of a new constant-time 3D triple-resonance experiment, ct-HA[CAN]HN, is presented. This experiment delineates exclusively scalar connectivities and uses 13Cα15N heteronuclear two-spin coherence to overlay the chemical shift evolution periods of the 13Cα and 15N nuclei, thereby providing the four resonance frequencies of the α-proton, the α-carbon, the amide nitrogen, and the amide proton of a given amino acid residue in three dimensions. This experiment promises to be a valid alternative to 4D experiments, providing the same information on intraresidue polypeptide backbone connectivities in 13C-15N-double-labeled proteins.