Proton Assisted Insensitive Nuclei Cross Polarization

This Communication presents a solid-state NMR 15 N− 13 C polarization transfer scheme applicable at high B 0 and high MAS frequencies, requiring moderate rf powers and mixing time (1−6 ms). The sequence, PAIN-CP, involves the abundant nearby protons in the heteronuclear recoupling dynamics and provides a new tool for obtaining long distance 15 N− 13 C contacts. It should be of major interest for biomolecular structural studies.