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(δ) and C(α) chemical shifts of proline residues with the H(α) 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.