Correlated spectroscopy experiment

For compounds that contain a limited number of fluorine atoms, heteronuclear correlation spectroscopy experiments such as F H HETCOR and 2H-19F heteronuclear Overhauser enhancement spectroscopy (HOESY) can provide considerable assistance distinguishing structural isomers and diastereomers as well as for conformational analysis. HOESY experiments have been frequently used for conformational analysis of biomolecules containing fluorine labels.18... 

The first fluorescence correlation spectroscopy experiments were carried out several decades ago,62 64 but the general use of the technique was made possible with the introduction of lasers with high beam quality and long-term temporal stability, low noise detectors, and high-quality microscope objectives with high numeric apertures.58,63 The most common set-up is using a confocal inverted epi-fluorescence... 

C- H correlation spectroscopy experiments. " The spectra show no coupling between " C and... 

Two-dimensional COSY (correlation spectroscopy) experiments allow determination... 

The 2D homonuclear TOCSY (Total Correlation SpectroscopY) experiment... 

In the H- H COSY (correlation spectroscopy) experiment (41), magnetization is transferred via the J-coupling and shows correlations between protons three bonds apart. The cross peak usually shows a characteristic antiphase-square pattern, but it may be split even more by additional passive couplings that lead to spectral crowding and loss of intensity. For small molecules. 

Broadband Hartmann-Hahn transfer can also be of assistance in alternative approaches to determine coupling constants that do not rely on E.COSY-type multiplets that are separated by large one-bond couplings. The homonuclear two-dimensional PICSY (pure in-phase correlation spectroscopy) experiment (Vincent et al., 1992, 1993), which is based on selective Hartmann-Hahn transfer using doubly selective irradiation, can... 

Figure 2.5 Relaxation rates F of the intensity correlation functions as a function of q2 obtained via a photon correlation spectroscopy experiment. The sample was a w/o-droplet microemulsion made of D2 0/n-octane-di8/CioE4. On the oil-continuous side of the phase diagram the scattered light intensity is usually low leading to rather large errors of the individual data points. Nevertheless, from the slope of the linear fit the translational diffusion coefficient is obtained. (Figure redrawn with data from Ref. [67].)...

One of the most important uses of distance geometry is for deriving conformations that are consistent with experimental distance information, especially distances obtained from NMR experiments. The NMR spectroscopist has at his or her disposal a range of experiments that can provide a wealth of information about the conformation of a molecule. Two of the most commonly used NMR experiments that provide such conformationally dependent information are the 2D-NOESY (nuclear Overhauser enhancement spectroscopy) and the 2D-COSY (correlated spectroscopy) experiments [Derome 1987]. NOESY provides information about the distances between atoms which are close together in space but may be separated by many bonds. The strength of the NOESY signal is inversely proportional to the sixth power of the distance and so by analysing the nuclear Overhauser spectrum it is possible... 

Dispersions of polyaniline in isopropanol-based organic solvents were investigated by photon correlation spectroscopy experiments and the results of these experiments are shown for neutral PAni in Figure 11,41 and for doped PAni in Figure 11,42, Therefore it is important to note that the dispersions used (0,1% concentration) are completely clear and have been filtered through 1 pm filters or pressure filtered through membrane filters [84],... 

A new through-bond correlation method for disordered solids has been proposed. The new approach is based on the uniform-sign cross-peak double quantum filtered correlation spectroscopy experiment, which is a refocused version of the popular double quantum filtered correlation spectroscopy experiment in liquids. Its key feature is that it provides in-phase and doubly absorptive line shapes, which renders it robust for chemical shift correlation in solids. It has been shown that both theory and experiment point to distinct advantages of this protocol, which are illustrated by several experiments under challenging conditions, including fast MAS up to 30kHz, anisotropic molecular motion, and correlation spectroscopy at the natural abundance isotope level. 

The interpretation of ROESY experiments is not devoid of complications and hence, if the molecular tumbling frequencies allow it, NOESY experiments are to be preferred. One of the complications of ROESY experiments is the possible appearance of cross-peaks originating from scalar coupling instead of cross-relaxation. These crosspeaks have the same origin as the ones that are observed in TOCSY (total-correlation spectroscopy) experiments and can be distinguished from the cross-relaxation peaks because they have opposite sign. However, TOCSY crosspeaks may cancel with NOESY peaks involving the same protons. 

In Section 4.12.2, we described pulse sequences that have one or more time intervals between the pulses. The duration of these intervals is of great importance, and the appearance of the spectrum obtained in each case changes as the intervals are varied. Without going into the detail of pulse sequences, we illustrate this in Figure 4.51 with the pulse sequence for the simplest 2D-NMR experiment, the COSY (Correlated SpectroscopY) experiment, which correlates resonances of nuclei of the same kind, if the individual resonances are related by scalar coupling. 

Photon correlation spectroscopy experiments have been carried out in completely clear and filtered (membrane filters) dispersions (0.1% concentration) of polyaniline in isopropanol-based organic solvents (Fig. 19.41) [42]. 

The COSY (correlation spectroscopy) experiment has become one of the mainstays of modern NMR spectroscopy it is also one of the simplest... 

The most useful experiment of all is the homonuclear COSY (two-dimensional homonuclear Correlated SpectroscopY) experiment. This yields a square matrix of data. The diagonal, projected onto either frequency axis, is the normal one-dimensional spectrum, and off-diagonal multiplets appear with the x coordinate of resonance A and the y coordinate of resonance B or vice versa, when A and B are mutually spin-coupled. A two-dimensional spectrum of this type is most conveniently presented as a contour diagram, as viewed from above, even though such maps seem at first strange to one-dimensional spectroscopists. 

---