Methods for sequential resonance assignment in solid, uniformly C-13, N-15labelled peptides: Quantification and application to antamanide

The application of adiabatic polarization-transfer experiments to resonance assignment in solid, uniformly C-13-N-15-labelled polypeptides is demonstr ated for the cyclic decapeptide antamanide. A homonuclear correlation exper iment employing the DREAM sequence for adiabatic dipolar transfer yields a complete assignment of the C-alpha and aliphatic side-chain C-13 resonances to amino acid types. The same information can be obtained from a TOBSY exp eriment using the recently introduced P9(12)(1) TOBSY sequence, which emplo ys the J couplings as a transfer mechanism. A comparison of the two methods is presented. Except for some aromatic phenylalanine resonances, a complet e sequence-specific assignment of the C-13 and N-15 resonances in antamanid e is achieved by a series of selective or broadband adiabatic triple-resona nce experiments. Heteronuclear transfer by adiabatic-passage Hartmann-Hahn cross polarization is combined with adiabatic homonuclear transfer by the D REAM and rotational-resonance tickling sequences into two- and three-dimens ional experiments. The performance of these experiments is evaluated quanti tatively.