Homonuclear Correlation Experiments

Homonuclear correlation experiments are not just restricted to the standard COSY experiment, but also include the TOCSY and INADEQUATE experiments. The separation of TOCSY and INADEQUATE from the homonuclear COSY experiment is based on the different coherence evolution and transfer processes involved. Thus the TOCSY experiment is based on cross-polarization in contrast to the polarization transfer used in the homonuclear COSY experiments. INADEQUATE experiments are characterized by the double quantum state of two scalar-coupled nuclei during the tl period such that the second dimension (fl) is scaled into a double quantum frequency. Nevertheless these experiments can all be considered together because they are based on homonuclear scalar coupling and the fl and f2 dimension of the corresponding 2D spectra are related to the same nucleus. 

Homonuclear polarization transfer and coherence detection which evolve due to the chemical shift of one nucleus in the tl period 

In contrast to homonuclear COSY experiments in 2D heteronuclear correlation experiments the two frequency dimensions are assigned to different nuclei. The term COSY is often used to imply homonuclear correlation and in particular H, IH correlation. Consequently heteronuclear correlation experiments either have a specific name related to the processes involved such as IH HMQC or simply have the words COSY experiment appended to the detected nuclei as in IH, l c COSY experiment. 

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In homonuclear correlation experiments, swi is almost always set equal to sw2- In addition, reduced spectral widths are used in both dimensions to improve digital resolution. The reduced sw s are set equal to the distance between the highest- and lowest-frequency signals. 

Hetero- and Homonuclear Correlation Experiments Involving MQMAS... 

HETERO- AND HOMONUCLEAR CORRELATION EXPERIMENTS INVOLVING MQMAS... 

MQMAS has further opened up vistas by making it possible to design high-resolution hetero- and homonuclear correlation experiments. These lead to connectivity information, distance measurements, and spectral editing. 

These aspects can be of particular relevance in three-dimensional homonuclear correlation experiments, where a cubic diagonal may prohibit a detailed structural analysis. As visible from Fig. 5, these effects can be minimized by conducting a 3D 2QC-1QC-1QC experiment. The general transfer pathway carried out by the pulse sequence shown in Fig. 5a is as follows ... 

Correlation experiments by polarization transfer Homonuclear correlation experiments... 

The HOHAHA or TOCSY experiment [5.150, 5.151] has proved a popular alternative in many applications to the main homonuclear correlation experiment for sensitive nuclei, the basic COSY experiment. Both the HOHAHA and the TOCSY experiment are based on the principal of isotropic mixing but differ in the type of spinlock sequence used. Nevertheless they may be considered together and for convenience in the following discussion the expression TOCSY experiment will be used for both sequences. The TOCSY experiment uses cross polarization for the coherence... 

Starting with the basic INADEQUATE experiments the simulation focuses on the inherent disadvantage of homonuclear correlation experiments on nuclei with low natural abundance. 

Most homonuclear correlation experiments rely on the homonuclear dipolar couplings to provide information... 

Uniform and labeling provides improved signal dispersion and editing by multidimensional experiments or filtering by isotope or spin-state as well as various routes for coherence transfer and ways to measure scalar and dipolar couplings. Solvent suppression in heteronudear correlation experiments is also much easier than in homonuclear correlation experiments. 

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