Rotating frame Overhauser effect spectroscopy ROESY

In order to combat this, the rotating frame Overhauser effect spectroscopy (ROESY) techniques can be employed. An in-depth discussion of how this technique works is outside the remit of this book but suffice to say, in the ROESY methods (1- and 2-D), NOE data is acquired as if in a weak r.f. field rather than in a large, static magnetic field and this assures that all NOEs are present and positive, irrespective of tumbling rate and magnet size. It is possible that some TOCSY correlations can break through in ROESY spectra but these will have opposite phase to the genuine ROESY correlations and so should therefore not be a problem - unless they should overlap accidentally with them. A 2-D ROESY spectrum of the naphthalene compound is shown below (Spectrum 8.6). 

NOE becomes negligible and no cross-peaks are observed), which correlates well with IR measurements and theoretical calculations on the same system By deuteriating 95% of the cations and repeating the experiment, they determined the existence of intermolecular NOE transfer. In this work, the rotating-frame Overhauser effect spectroscopy (ROESY) experiment was performed, as it is more suitable for very viscous materials and requires shorter mixing time (reducing the overall experiment time). For a full description of the ROESY experiment, the reader is referred to the excellent text by Jacobsen et al. [34]. 

At 500 MHz, moderate-sized (more than six residues) oligosaccharides lie within the spin-diffusion limit. However, for smaller molecules, as the value of the function (OqT (where (Oq is the Larmor frequency of protons, and is the correlation time of the molecule) approaches 1 then the value of the NOE tends towards 0. Cross-peak intensities of NOESY spectra of smaller oligosaccharides (2-5 residues) may thus become too small to measure accurately. In such cases, the rotating frame Overhauser effect spectroscopy (ROESY, originally referred to as CAMELSPIN) experiment is commonly used to measure NOE values. To reduce the appearance of HOHAHA-like cross-peaks, a low power spin-lock field should be used, and the transmitter carrier offset to the low-field end of spectrum. The offset dependency of cross-peak intensities should also be removed by 90° pulses at either end of spin-lock period. 

ROESY Rotating-frame Overhauser effect spectroscopy. A variation (one and two dimensional) on the nuclear Overhauser experiment (NOE). The techniques have the advantage of being applicable for all sizes of molecule. See Laboratory frame model. 

Various studies were focusing on the conformational behavior of the cinchonan carbamate selectors in free and complexed form, which could readily be derived from the dihedral coupling constant of the Hs-Hg protons ( /hsh9) and intramolecular NOEs as measured by 2D-NOESY [92,93] or two-dimensional rotating frame Overhauser effect spectroscopy (2D-ROESY) [65] spectra. 

ROESY Rotating Frame Overhauser Effect SpectroscopY... 

ROESY rotating frame overhause effect spectroscopy... 

In Chapter 3 (Section 3.16), there is a description of the nuclear Overhauser effect difference experiment, an experiment that provides information about H— H through-space proximity. Review of this section is helpful before proceeding here. The ROESY experiment, rotating-frame Overhauser effect spectroscopy, is a useful 2-D analogue of the nuclear Overhauser effect difference experiment. This experiment is useful for molecules of all sizes whereas the related experiment, NOESY (nuclear Overhauser effect spectroscopy), is not very useful with small molecules. NOESY is used primarily with biological macromolecules. Both NOESY and ROESY experiments correlate protons that are close to each other in space, typically 4.5 A or less. 

ROESY (rotating frame Overhauser effect spectroscopy) is a variant of NOESY, in which the transfer of magnetization occurs on the spin-lock axis in the x-y plane rather than on the z axis (Fig. B.9). A continuous low-power radio frequency pulse provides the mixing by effectively reducing the field strength (Bq in the laboratory frame on the z axis to B in... 

NMR experiments include COSY, TOCSY, Cheteronuclear NMR experiments, NOESY (nuclear overhauser enhancement spectroscopy) and ROESY (rotating frame overhauser effect spectroscopy) as well as other two- and three-dimensional methodologies (Fossen and Andersen, 2006). 

ROESY Rotating-frame Overhauser Effect Spectroscopy... 

Several physical methods have been employed to ascertain the existence and nature of ICs infrared (IR) absorption spectroscopy nuclear magnetic resonance (NMR) spectroscopy,14 including JH nuclear Overhauser effect (NOE) difference spectroscopy, H 2-D rotating-frame Overhauser effect spectroscopy (2-D ROESY),15 and solid-state 13C cross-polarization/magic angle spinning (CP/MAS) spectroscopy 16 induced circular dichroism (ICD) absorption spectroscopy 17 powder and singlecrystal X-ray diffraction 18 and fast atom bombardment mass spectrometry (FAB MS). 

ROESY Rotating-frame Overhauser effect spectroscopy 8.8... 

NOESY and ROESY are the acronyms for nuclear Overhauser effect spectroscopy and rotation-frame Overhauser effect spectroscopy. 

The best way to avoid the l-cox problem (and weak nOes) is to use a rotating frame experiment, for instance ROESY (Rotating frame Overhauser Effect Spectroscopy) also named CAMELSPIN by its inventors (77). The (oXg dependence of rOes is complex and one may simply remember that rOes are always positive, never null. The ROESY sequence is similar to the sequence of HOHAHA the main difference is the power of the spinlock which is generated by a long soft pulse rather than by a WALTZ sequence. In ROESY experiments, rOe cross peaks may be accompanied by Hart-mann-Hahn correlations which are easily distinguished by their opposite sign (in phased experiments) (78). 

Heteronuclear Multiple Quantum Correlation) and HMBC (Heteronuclear Multiple Bond Correlation). Application of nuclear Overhauser effect (nOe) difference spectroscopy and nuclear Overhauser effect spectroscopy (NOESY) complete the analysis, giving atomic spatial relationships. Sensitivity problems can be alleviated using Homo Hartmann-Hahn spectroscopy (HOHAHA or TOCSY, Total Correlation Spectroscopy). For weak nOes a rotating frame experiment, i.e. ROESY (Rotating frame Overhauser Effect Spectroscopy) is useful, and may be the best experimental method to sequence chains of sugars [5]. 

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