Heteronuclear single-quantum coherence HSQC

Fig. 10.3 Heteronuclear single quantum coherence (HSQC, panel a) and NMR...

Record the 2-D H-13C heteronuclear single quantum coherence (HSQC) spectrum (Braun et al., 1998, pp. 497-500). 

In order to carry out complete structural elucidation of unknown compounds (especially for complex molecules), the RF probe should enable a variety of heteronuclear NMR techniques to be performed. In particular, inverse detection H-15N and 1H-13C experiments such as heteronuclear multiple quantum coherence (HMQC) [29,30] and heteronuclear single quantum coherence (HSQC) [31] find almost ubiquitous application in myriad research environments. Although the microliter-scale probes described above feature both heteronuclear and homonuclear capabilities, no commerical product is... 

NMR) studies. The protein was mostly recovered in soluble form (see Fig. 6, lanes T, S of At03). To probe its folding state, heteronuclear single-quantum coherence (HSQC) with 157V-labeled FT protein (four amino acids—Gly, Ala, Leu, and Gin, replaced with 157V-labeled versions) was measured by NMR. The distribution of resonances in the 2D 15/V-XH correlation spectrum shows a reasonable number of signals and indicates that the protein is folded in solution... 

This chapter describes protocols for preparing 15N-labeled proteins (ubiquitin is used as an example) using Escherichia coli cells (with purification) and the wheat germ cell-free system (without purification). A comparison of I I-15N heteronuclear single-quantum coherence (HSQC) spectra of yeast ubiquitin prepared using each method indicates that this wheat germ cell-free system may be used for rapid nuclear magnetic resonance analyses of proteins without purification. 

The synthesized yeast ubiquitin labeled with 15N with both the E. coli and wheat germ cell-free systems can now be analyzed by NMR. Here, the outline of the procedure for NMR JH-15N heteronuclear single-quantum coherence (HSQC) measurements and the comparison of both spectra are described. 

Fig. 6. H- SN heteronuclear single-quantum coherence (HSQC) spectrum of yeast ubiquitin overexpressed mEscherichia coli cells and purified (1.0mA/, 128 [tl] 1024 [t2] complex points, 64 scans), obtained at the H resonance frequency of 500 MHz. Spectral widths are 1600 and 6250 Hz in Ft and F2, respectively.

It is not necessary that the evolving 13C coherences be detected immediately. As shown in Section 9.6, they can be allowed to precess until they are in phase, then detected while protons are decoupled to provide a single enhanced signal. Alternatively, the entire INEPT sequence can be treated as the preparation period of a 2D experiment. The coherences then evolve during a period t, and can be manipulated in various ways by further pulses. One of the most commonly used methods is to apply a second INEPT sequence, without the initial 90v pulse, after the evolution period to convert the 13C coherences back into H coherences, which can be observed. As we mentioned in Chapter 10, this method, heteronuclear single quantum coherence (HSQC), is widely employed to obtain... 

FIGURE 12.9 Example of heteronuclear single quantum coherence (HSQC) applied to allylbutyl ether (300 MHz).The correlations of H and 1 C chemical shifts are clearly shown. Note the similarity to Fig. 10.10, which displays a HETCOR spectrum. For a sample of this sort, where signal/noise ratio is no problem, there is little to choose between the two techniques, but HSQC is inherently much more sensitive. 

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. 

Is the probe direct, or inverse The former is good for direct observation with or without INEPT enhancement. The latter will give poor signaTto-noise in direct experiments since the sample does not fill the coil space, but is much preferred for indirect detection via, for example, a heteronuclear multiple quantum coherence (HMQC) or heteronuclear single quantum coherence (HSQC) experiment. 

C-H correlation over one bond Heteronuclear multiple quantum coherence (HMQC), heteronuclear single quantum coherence (HSQC)... 

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... 

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