A new 1H 15N 13C triple-resonance experiment for sequential assignments and measuring homonuclear H αH N vicinal coupling constants in polypeptides

Abstract

We have developed a ‘H“N13C triple-resonance experiment that provides accurate measurements of homonuclear H *-H N coupling constants in polypeptides. The pulse sequence also results in sequential and intraresidue cross peaks that can be distinguished from their different cross-peak structures. The experiment yields in part patterns similar to those of a technique we had developed earlier (1, 2). The previously described technique uses successive one-bond coherence transfers from HP to CT( w1 ), Ni, and Hr( wz). Simultaneously two-bond coherence transfer occurs from HE, to C; 1 ( w , ) , Ni, and H y ( w2) (2). This sequence provides, at the w2 frequency of each HN, two cross peaks, an intraresidue CT( w1 )-Hr( w2) cross peak, and a sequential C ;, ( w , ) -H r ( w2) cross peak. The intraresidue cross peak consists of two components at