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The ge-2D multiplicity-edited HSQC experiment is a simple modification of the ge-2D HSQC experiment in which carbon multiplicity can be directly extracted from the resulting spectra in addition to the conventional heteronuclear correlations by simple analysis of the cross-peaks sign.REQUIREMENTS
Easy implementation on any AVANCE spectrometer equipped with pulsed field gradients (PFGs) and inverse probehead.VERSIONS
In the conventional ge-2D HSQC pulse scheme, the dephasing gradient G1 is usually placed into an heteronuclear spin-echo, d-180°(X)-G(d), at the end of the t1 period in order to avoid offset and coupling evolutions during the application of this gradient (see scheme a). If this block is substituted by a D´-180°(X)/F°(1H)-D´ block (D´=1/2*(1JCH)), a X-signal intensity dependence of cos(n-1)F appears as a function of the HnX system ( 97JMR274-126 ). In the more general approach, F is set to 180º and, therefore, a concatenated building block can be derived that avoids the application of an extra proton 180 pulse (see scheme b).EXPERIMENTAL DETAILSCarbon multiplicity information can be introduced in any HSQC scheme giving pure absorption data using the following 13C-evolution block:
This block can be succesfully implemented in any version of phase-sensitive HSQC experiment: i) using a 13C z-filter; ii) using the echo-antiecho approach; and iii) using the PEP methodology. Maximum sensitivity is obtained by a simple modification of the later version ( 97JMR274-126 ).
The ge-2D multiplicity-edited HSQC experiment can be recorded in routine/automation modes. Minor changes are required if a predefined parameter set is available. The user must define the strength, the duration, and the shape of the gradients and the recovery delay.SPECTRAMore details on practical implementation of ge-2D HSQC experiments on AVANCE spectrometers can be found in
Tutorials: 2D inverse experiments Tutorials: 2D gradient-based inverse experiments
The multiplicity-edited HSQC spectrum correlates chemical shifts of heteronucleus X (F2 dimension) and protons (F1 dimension) via the direct heteronuclear coupling 1J(XH). Methine and methyl protons will appear as positive signals whereas methylene protons will present negative intensity. The effective suppression of unwanted 1H-12C or 1H-14N magnetization by means of PFGs allows to obtain ultra-clean 2D spectra from which clear analysis can be done.RELATED TOPICS
Related experiments:
Other related editing approaches based on the selection of specific Multiple-Quantum coherences (MQCs) have been proposed ( 01COC351 ): In all these experiments, PFGs are used to select specific n-quantum coherences that can simplify the analysis of high overlapped spectra although sensitivity losses are unavoidable due to coherence selection. This experiments can be also referred as ge-2D HmQC (Heteronuclear Multiple-Quantum) experiments. Thus, depending of the gradient-based filter used a HDQC (Heteronuclear Double-Quantum) experiment, HTQC (Heteronuclear Triple-Quantum) experiment, or HQQC (Heteronuclear Quadrupole-Quantum Experiment) experiment results.2D Inverse experiments 2D Inverse gradient-enhanced experiments
