The 3D HC(CN)H experiment has been proposed to achieve unambiguous assignment of the exhangeable imino proton resonances to the nonexchangeable purine H8 and pyrimidine H6 protons in ¹³C,¹⁵N-labeled nucleic acids.

2D H(CCCN)H versions have been also proposed:

Implementation on AVANCE spectrometers equipped with a third channel and gradient technology.

The original experiment was described in ( 96JB83 , 96JACS689 ). Related experiments are

2D H6/H5(C4N)H and C6/C5(C4N)H for pyrimidine bases ( 03JB79-26 )

A related 2D C5(C6N)H has been proposed for resonance assignment of the quaternary carbon C5 in guanines ( 04JB69-28 )

In the H(CC)NH spectra, all H/N pairs are correlated to H6/H8 protons in a third dimension.

Also see Assignment of exchangeable imino and amino proton and nitrogen resonances