ROESY experiments

Additional significant spatial correlations (NOE) in the HH ROESY experiment (c) provide information concerning the distances of some protons from one ring (at C-9) to the other (at C-1). Such closely spaced protons are ... 

Figure 5.45 Pulse sequence used in the ROESY experiment. The data obtained from odd and even scans are stored separately.

The pulse sequence for the ID ROESY experiment using purged half-Gaussian pulses is shown in Fig. 7.7. The purging is required to remove the dispersive components, since these are not completely eliminated by the weak spin-lock field employed in the ID ROESY experiment. 

Parhcular care has to be taken when implementing ROESY experiments. The spin-lock, which holds the spins along a defined axis perpendicular to the stahc magnetic field, can be realized in many different ways and is shU an achve field of research [18, 20]. In most spin-lock sequences the conditions for undesired TOCSY transfer are parhally fulfilled and especially cross-peaks close to the diagonal or anhdiagonal might not be accurately interpretable. Since in most cases the effechveness of the spin-lock also depends on the chemical shift offset, an offset-dependent correction has to be applied to the measured cross-peak intensities [20]. 

We have tried to point you in the direction of the experiments that we have come to use and rely on, with good reason. There are dozens more out there that have been developed some have evolved and are now generally known by another name (e.g., the ROESY experiment used to be known as CAMELSPIN) and some have been superseded and fallen by the wayside. If you have the instrument time and the inclination, by all means play but if time is of the essence, as it usually is, stick with the safe options. 

The data from H NMR studies of 63, which included double quantum filtered phase sensitive correlated spectroscopy (DQF-COSY) and rotating frame nuclear Overhauser effect spectroscopy (ROESY) experiments (Figure 12), are collected in Table 17. 

For situations where the product of the resonance frequency and the overall correlation time of a molecule approaches unity NOE effects are close to zero. Under these circumstances the proximity of spins in space can still be inspected in the rotating frame by the ROESY experiment. This is usually the case for small oligosaccharides and oligopeptides at higher magnetic fields. 

In both ID ROESY-TOCSY and ID TOCSY-ROESY experiments [72] (figs 7(c), (d)) magnetization was stored along the 2 axis at the joining point... 

The ID TOCSY-ROESY experiment is illustrated on the same molecule using the pulse sequence of fig. 7(d). This time the magnetization of H-4c was generated during the initial selective TOCSY transfer from H-lc (fig. 9(b), pulse sequence of fig. 7(b)). In the subsequent ID TOCSY-ROESY experiment, the ROE transfer from H-4c confirmed the expected... 

The ROESY experiment [8] overcomes this problem by measuring crossrelaxation rates in the rotating frame. Their dependence on the correlation time, Tc, is now given by... 

The ID TOCSY module has been used in many pseudo-3D experiments (or alternatively referred to as ID analogues of 3D experiments in the literature) such as ID TOCSY-NOESY or ID TOCSY-ROESY experiments. The TOCSY part of these experiments are similar to that of a regular ID TOCSY where a selective excitation of a desired signal is followed by a MLEV17-type isotropic mixing. The second polarization transfer (NOESY or ROESY) step can either be non-selective [29, 59-61] or selective [62-65]. 

In the following, three different experiments are discussed, where short, high-power spin-lock pulses are used to purge the spectrum from undesired resonances. The experiments are (i) the HSQC experiment [5], (ii) experiments with C half-filter elements [6], and (iii) NOESY and ROESY experiments for the observation of water-protein NOEs [7]. In the first two experiments, spin-lock purge pulses are used to suppress the signals from... 

More serious are the coherence transfer cross peaks in ROESY spectra because the coherence peaks are in phase with the genuine cross-relaxation peaks and thus may modulate intensity of the genuine peaks. To emphasize the effect of coherence transfer peaks (now TOCSY peaks) we do the ROESY experiment with Tm = 300 ms and with a spin-lock field of 5 kHz (fig. 4(C)). Besides positive diagonal peaks (thick contours), several pairs... 

The easiest way to reduce the amplitude of TOCSY cross peaks in the ROESY spectra is to record a spectrum with minimal spin-lock power [23]. The other possibility is to modulate the frequency of the spin-lock field [25]. However, the most convenient way is to apply a series of 180° pulses instead of a single continuous-wave pulse during the mixing time, as is done in the T-ROESY experiment. Figure 4(D) shows the T-ROESY spectrum of cyclo(Pro-Gly) recorded with = 300 ms. Although the... 

Nymphaea caerulea, for seven natural anthocyanins stabilizing a DNA triplex, etc. Sequential analysis of the oligosaccharide structures of the flavonol tamarixetin-7-O-rutino-side has been performed by ID multistep-relayed COSY-ROESY experiments. Selective excitation was performed by Gaussian-shaped soft pulses. 

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