A novel NMR experiment for the sequential assignment of proline residues and proline stretches in 13C/15N-labeled proteins.

A new pulse sequence is described for the sequential assignment of proline residues in 13C/15N-labeled proteins by correlating C delta and C alpha chemical shifts of proline residues with the H alpha chemical shift of the preceding residue. Notably, the experiment can provide the sequential connectivities in poly-proline stretches, which cannot be determined using standard triple resonance experiments. Excellent solvent suppression is achieved by coherence selection via a heteronuclear gradient echo. The new pulse sequence has been successfully applied to the 11 kDa HRDC domain.