Heteronuclear single quantum assignment

Introducing a heteronuclear dimension reduces the signal overlap by using the additional chemical shift dispersion of the heteronuclei and facilitates assignment of biomolecules. The Heteronuclear Single Quantum Correlation (HSQC) experiment yields a spectmm that correlates the chemical shift of a spin with that of a covalently bound or spin (55). In a HSQC spectrum, every peak represents the correlation of an amide bond, which shows correlations... 

Traditionally, homonuclear 2D double quantum filtered correlation spectroscopy (DQF-COSY) and total correlated spectroscopy (TOCSY) spectra are valuable in the identification of resonances of individual monosaccharide units. In the presence of small couplings, through space connectivities detected by NOESY/ROESY (nuclear Overhauser effect spectroscopy/ rotational nuclear Overhauser effect spectroscopy) experiments are also useful in completing the resonance assignment. When the H NMR spectra of complex oligosaccharides are too crowded to fully elucidate the structure by homonuclear correlation methods, it is efficient to use 2D heteronuclear correlation methods, such as heteronuclear single quantum correlation... 

The assignment of heteronuclei generally requires acquisition of a heteronuclear single quantum coherence (HSQC) experiment and a heteronuclear multiple bond correlation (HMBC) experiment, and these are described in more detail below. 

The final step in the assignment of all resonances is correlating the C peaks with the proton peaks. This can often be done from chemical shift alone for the anomeric resonances, but not for other ring atoms. The most important pulse sequence here is HSQC (Heteronuclear Single Quantum Correlation), which involves six pulses to protons and four to C. The spectrum is now a non-symmetrical map with a peak at each carbon attached to a proton the projection on the C axis is the C DEPT spectrum and on the proton axis the ordinary proton spectrum (Figure 4.18). 

Further 2-D H total correlation spectroscopy (TOCSY) anal3rsis of fire humate from the cellulose treatment indicates that this region is rich in aCH and CH2 of amino acid residues phis CH/CH2 of polysaccharides (Figure 6). These assignments were made based on the proton covalent connectivity and chemical shift information acquired from the TOCSY spectrum, and are in agreement with the 2-D heteronuclear single quantum coherence (HSQC) analysis... 

The copolymers of acrylonitrile with methyl methacrylate (A/M), Glycidyl methacrylate (A/G) and acrylic acid (A/B) of different monomer concentrations were prepared. The carbon-13 and proton spectra of these copolymers are overlapping and complex. The complete spectral assignment of and NMR spectra were done with the help of Distortionless Enhacement by Polarisation transfer (DEPT) and two dimensional Heteronuclear Single Quantum Correlation... 

Similarly, PPI dendrimers have shifts that are very similar for each repetitive layer, and to completely assign these strac-tures more complex methods such as 2D-NOESY (two-dimensional nuclear Overhauser enhancement spectroscopy) and 3D-NOESY-HSQC (HSQC, heteronuclear single quantum coherence) have been used. These methods will be discussed in the following. ... 

M. Takasaki, K. Kimura, Y. Nakagawa, N. Sato, B. Bae, K. Miyatake, M. Watanabe, Complete NMR assignment of a stdfonated aromatic block copolymer via heter-onuclear single-quantum correlation, heteronuclear multiple-bond correlation and heteronuclear single-quantum correlation total correlation spectroscopy, Polym. J. 44 (2012) 845-849. 

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