Triple resonance experiments are a set of multi-dimensional nuclear magnetic resonance spectroscopy (NMR) experiments that link three types of atomic nuclei, most typically consisting of 1H, 15N and 13C.
[3][4] There are two main methods of determining protein structure on the atomic level.
These problems may be alleviated by using heteronuclear NMR spectroscopy which allows the proton spectrum to be edited with respect to the 15N and 13C chemical shifts, and also reduces the overlap of resonances by increasing the number of dimensions of the spectrum.
In 1990, Ad Bax and coworkers developed the triple resonance technology and experiments on proteins isotopically labelled with 15N and 13C,[1] with the result that the spectra are dramatically simplified, greatly facilitating the process of resonance assignment, and increasing the size of the protein that may be determined by NMR.
These triple resonance experiments utilize the relatively large magnetic couplings between certain pairs of nuclei to establish their connectivity.
[3] Triple resonance experiments involving 31P may also be use for nucleic acid studies.
The sidechain carboxamide of glutamines and asparagines also appear in this spectra in this experiment.
CBCA(CO)NH is sometimes more precisely called (HBHA)CBCA(CO)NH as it starts with aliphatic protons and ends on an amide proton, and is therefore not an out-and-back experiment like HN(CO)CACB.
The CBCANH experiment is less suitable for larger protein as it is more susceptible to the line-width problem than HNCACB.
This experiment provides the connectivities between the Cα and Cβ with the carbonyl carbon and Hα atoms within the same residue.
[13] The sidechain carboxyl group of aspartate and glutamate may appear weakly in this spectrum.
This experiment correlates the amide resonance to the Hα and Hβ of the preceding residue.