Correlated spectroscopy advantages

Two-dimensional spectroscopy is a rather novel concept, and a powerful tool in analysing spectra. The advantages of generalised 2D correlation spectroscopy are ... 

We now want to turn to another experiment which, we must make clear at the start, does not have any relationship in theory to NOE experiments. In fact the theory is so complicated that we shall not say anything about it at all, but just refer you to one of the books in the Appendix. We are including this experiment because of its unique advantages when the spectrum has overlapping multiplets. It is called TOCSY, which stands for Total Correlation SpectroscopY (it has a second, more amusing name HOHAHA, standing for HOmonuclear HArtmann-HAhn), and is of particular use when oligosaccharides or peptides are under study. 

IV. Advantages and Disadvantages of Using Fluorescence Correlation Spectroscopy to Study Protein Conformational Changes... 

In summary, the advantage of using fluorescence correlation spectroscopy is that very small sample volumes can be employed and the system is studied at equilibrium without the need to perturb the chemical equilibrium. The disadvantages of the technique are difficulties in differentiating between artifactual signals and relaxations related to chemical phenomena and the development of suitable models for fitting the correlation curves. 

The additional advantage of CARS-CS over DLS and FCS is the spectral selectivity for individual chemical components in their native state, where fluorescent labeling is not desired. This may not only allow mapping of 3D diffusion coefficients, for example inside life cells, but also offer a method to monitor the specific interaction of individual components within complex systems, e.g., aggregation processes of different chemical species. Another prospect is the implementation of CARS cross-correlation spectroscopy that may allow the investigation of correlated fluctuations between two different species. These could be two distinct Raman spectral features of one and the same compound, or a specific intrinsic Raman band and an emission of a more sensitive fluorescence label [160]. 

Coupling FFF with other techniques can enhance measurement capabilities. Here, the possibility of taking fractions after the FFF separation is of great advantage. The use of photon correlation spectroscopy, for example, to determine the size of spheres eluted from sedimentation FFF yields both size and density [75]. Further comparison can be achieved with electron microscopy. In principle, every analytical technique (spectroscopy, microscopy, chemical analysis, etc.) can be performed off-line on fractions from FFF. 

It would be advantageous if we could retain the enhanced resolution afforded by the projection of the 2D J-resolved data and also obtain spin system connectivities. MAS spin-echo correlated spectroscopy (SECSY) (44) allows both spin connectivities and enhanced resolution to be obtained. The... 

NMR has become a standard tool for structure determination and, in particular, for these of Strychnos alkaloids. The last general article in this field was authored by J. Sapi and G. Massiot in 1994 [65] and described the advances in spectroscopic methods applied to these molecules. More recently, strychnine (1) has even been used to illustrate newly introduced experiments [66]. We comment, here, on their advantages and sum up the principles of usual 2D experiments in Fig. (1) and Fig. (2) (COSY Correlation SpectroscopY, TOCSY TOtal Correlation SpectroscopY, NOESY Nuclear Overhauser Enhancement SpectroscopY, ROESY Rotating frame Overhauser Enhancement SpectroscopY, HMQC Heteronuclear Multiple Quantum Coherrence, HMBC Heteronuclear Multiple Bond Correlation). This section updates two areas of research in the field new H and 13C NMR experiments with gradient selection or/and selective pulses, 15N NMR, and microspectroscopy. To take these data into account, another section comments on the structure elucidation of new compounds isolated from Strychnos. It covers the literature from 1994 to early 2000. 

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