Heteronuclear single-quantum coherence

HC HMQC (heteronuclear multiple quantum coherence) and HC HSQC (heteronuclear single quantum coherence) are the acronyms of the pulse sequences used for inverse carbon-proton shift correlations. These sensitive inverse experiments detect one-bond carbon-proton connectivities within some minutes instead of some hours as required for CH COSY as demonstrated by an HC HSQC experiment with a-pinene in Fig. 2.15. 

HSQC Heteronuclear single quantum coherence, e.g. inverse CH correlation via one-bond coupling providing the same result as HMQC but using an alternative pulse sequence... 

Fig. 10.15. Pulse sequence for the multiplicity-edited gradient HSQC experiment. Heteronuclear single quantum coherence is created by the first INEPT step within the pulse sequence, followed by the evolution period, t . Following evolution, the heteronuclear single quantum coherence is reconverted to observable proton magnetization by the reverse INEPT step. The simultaneous 180° XH and 13C pulses flanked by the delays, A = l/2( 1 edits magnetization inverting signals for methylene resonances, while leaving methine and methyl signals with positive phase (Fig. 16A). Eliminating this pulse sequence element affords a heteronuclear shift correlation experiment in which all resonances have the same phase (Fig. 16B).

Exploitation of the TROSY effect is rather straightforward. In contrast to 15N-HSQC (Heteronuclear Single Quantum Coherence) or standard triple-resonance experiments based on 15N-HSQC, no radio frequency pulses or composite pulse decoupling should be applied on amide protons when HN spin is not in the transverse plane. Likewise the 15N decoupling should be... 

FHSQC fast heteronuclear single-quantum coherence... 

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

FIGURE 2.1 heteronuclear single-quantum coherence spectrum of 5-carboxypyranocyanidin... 

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 12.8 Pulse sequence for the heteronuclear single quantum coherence experiment. See text for discussion of the state of the spin system at the times indicated. 

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. 

Heteronuclear multiple-quantum correlation Experiment for tailored correlation spectroscopy of H and H resonances in peptides and proteins Homonuclear Hartmann-Hahn spectroscopy Heteronuclear quadruple-quantum coherence Heteronuelear triple-quantum coherence Heteronuclear single-quantum coherence TOCSY sequences developed at the Indian Institute of Chemical Technology Insensitive nucleus enhancement by polarization transfer... 

Figure 1. Gradient-enhanced heteronuclear single quantum coherence pulse sequence with coherence transfer selection and artifact suppression gradients. All pulses are of phase x unless otherwise indicated.

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