A 13C- and 15N-edited triple-resonance ROESY experiment

A new triple-resonance pulse sequence that allows ¹³C and ¹⁵N editing of ROESY spectra is demonstrated. It incorporates filters that select for heteronuclear multiple-quantum coherence. The phase cycling provides efficient suppression of all peaks except those that originate from ROE magnetization transfer from protons coupled to ¹³ 3C to protons coupled to ¹⁵N. The loss in signal intensity caused by the filters is discussed. An application of the pulse sequence to a nonapeptide containing two ¹³C and two ¹⁵N labels is shown and compared to the conventional ROESY spectrum. The observed ROE indicate a significant population of a turn conformation for the peptide backbone.