Resonance assignment bond correlation

The heteronuclear multiple bond correlation (HMBC) experiment correlates proton nuclei with carbon nuclei that are separated by more than one bond. In Fig. FI. 4.7 the 37CH and 27Ch couplings dominate. Major applications related to anthocyanins include the assignment of resonances of nonprotonated carbon nuclei of the... 

Sidechain NHx assignments are obtained using modified 2D versions of the H- N HSQC, HNCO, HNCACB, and HN(CO)CACB experiments (10) to provide through-bond correlations of these sidechain Hn/ N resonances to the previously assigned sidechain C resonances. 

Fig. 9 Expansion of the HMBC spectrum of dutasteride in DMSO- e showing multiple bond correlations used to assign quaternary carbon resonances. Highlighted are correlations used to assign Cio, C13, and the carbonyl resonance C20, which is folded over in the dimension. Other correlations in the spectrum serve to confirm resonance assignments made based on results from the other experiments. (See Fig. 10 for structure and numbering scheme.)...

Mixing sequences for total through-bond correlation spectroscopy in solids (TOBSY) have been developed for fast MAS experiments. Possible sequences with the desired Hamiltonian (the homonuclear isotropic J interaction) have been identified using lowest order average Hamiltonian theory combined with numerical simulations as a function of the MAS frequency. An experimental TOBSY spectrum of a uniformly C-labelled decapeptide at 20 kHz MAS has been obtained using one of the new sequences. The spectrum allows to assign the resonances to the respective spin systems. 

Of course, the HSQC experiment is not the perfect solution for the detection of one-bond correlation spectra, since artefacts can also be observed. Some studies have determined the cause of these artefacts which can be assigned to off-resonance effects of the 180° pulses and H, H coupling [5.195, 5.196]. 

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