Bridging the gap: A set of selective 1H-15N-correlations to link sequential neighbors of prolines

Triple-resonance experiments are standard in the assignment of protein spectra. Conventional assignment strategies use ¹H-¹⁵N-correlations as a starting point and therefore have problems when proline appears in the amino acid sequence, which lacks a signal in these correlations. Here we present a set of amino acid selective pulse sequences which provide the information to link the amino acid on either side of proline residues and thus complete the sequential assignment. The experiments yield amino acid type selective ¹H-¹⁵N-correlations which contain signals from the amino protons of the residues either preceding or following proline in the amino acid sequence. These protons are correlated with their own nitrogen or with that of the proline. The new experiments are recorded as two-dimensional experiments and their performance is demonstrated by application to a 115-residue protein domain.