The 3D HCP experiment is a ¹H-¹³C-³¹P triple-resonance experiment specifically designed to assign the ribose H3'/C3', H4'/C4' on the 5' side and, H4'/C4' and H5',H5''/C5' resonances on the 3' side of the intervening phosphorus in ¹³C-labeled nucleic acids.

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

The 3D HCP pulse sequence ( 94JACS4983 and 94JACS6472 ) consists of the following basics steps:

1. Initial transfer from ¹H to ¹³C via ¹J(CH) using an INEPT pulse sequence.
2. Transfer from ¹³C to ³¹P via ⁿJ(CP) using another INEPT pulse sequence.
3. ³¹P chemical shift evolution during the variable evolution t₁ period.
4. Transfer back to ¹³C from ³¹P using a retro-INEPT pulse sequence.
5. ¹³C chemical shift evolution during the variable evolution t₂ period
6. Magnetization is finally transferred back to the ¹H protons using a CH-optimized PEP methodology.
7. Proton acquisition under ¹³C decoupling.

Other approaches:

Simultaneous acquisition of HCN and HCP experiments ( 96JB251 ).

An analog 2D H(C)P experiment has been proposed ( 95JMRB89-106 ).

A similar approach called HCPCH experiment has been proposed using natural abundance samples ( 95JMRB117-109 ).

Enhanced resolution in 3D HCP to measure 3J(C2'P) and 3J(C4'P) coupling constants ( 04JB61-30 )

Quantitative 2D and 3D HCP to measure ³J(C4'(i)-P(i)) and ³J(C4'(i)-P(i+1)) coupling constants in oligonucleotides ( 98JB223 ).

²J_C3'(i)-P(i) and ²J_{C5'(i+1)-P(i)} coupling constants are about 3-5 Hz, and ³J_C4'(i)-P(i) and ³J_{C4'(i+1)-P(i)} coupling constants are about 8-10 Hz

In the HCPCH spectra, the H-4'/C-4', H-3'/C-3', H-5',H-5''/C-5' pairs are sorted in a 2D spectrum as a function of ³¹P chemical shift in the third dimension.