ROESY spectroscopy

The structure, conformation and intramolecular hydrogen bonds of crystalline and aqueous sucrose have been discussed in detail. Evidence for a transient inter-residue hydrogen bond in aqueous sucrose (0-2- -H O-T) has been discovered by ROESY spectroscopy imder supercooled conditions.Combined use of high resolution NMR techniques and dynamics simulations furnished a new model for the dynamical conformational behaviour of sucrose in water in which internal motions occur at the same rate as overall tumbling. A GROMOS force field analysis, modified to include a potential energy term for the fxo-anomeric effect, has been assessed for efficiency by application to a conformational analysis of a-maltose. ... 

A comparison of the methods of proton-proton NOE detection has shown that two-dimensional NOE detection such as NOESY and ROESY are better suited to the investigation of the stereochemistry of biopolymers whereas for small- to medium-sized molecules (up to 30 C atoms) NOE difference spectroscopy is less time consuming, more selective and thus more conclusive. 

Oil and 0)2, and (b) 2D shift-correlation spectra, involving either coherent transfer of magnetization [e.g., COSY (Aue et al, 1976), hetero-COSY (Maudsley and Ernst, 1977), relayed COSY (Eich et al, 1982), TOCSY (Braunschweiler and Ernst, 1983), 2D multiple-quantum spectra (Braun-schweiler et al, 1983), etc.] or incoherent transfer of magnedzation (Kumar et al, 1980 Machura and Ernst, 1980 Bothner-By et al, 1984) [e.g., 2D crossrelaxation experiments, such as NOESY, ROESY, 2D chemical-exchange spectroscopy (EXSY) (Jeener et al, 1979 Meier and Ernst, 1979), and 2D spin-diffusion spectroscopy (Caravatti et al, 1985) ]. 

Multidimensional spectraas well as techniques including DEPT (distortionless enhancement by polarization transfer), COSY (correlated spectroscopy), and ROESY (rotating-frame overhauser enhancement spectroscopy) have been increasingly used. 

ROESY Rotating-frame Overhauser enhancement spectroscopy... 

The oldest and most widely used structural restraints in NMR spectroscopy are distance restraints derived from NOE experiments [1]. Transient NOE, 2D NOESY and ROESY spectra provide valuable information for interatomic distances up to 5 A that will be discussed in the following. 

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). 

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. 

Conformations of mycothiol bimane (MSmB) were studied by H and 13C NMR using rotational nuclear Overhauser effect spectroscopy (ROESY) and heteronuclear single quantum correlation (HSQC) methods with expansions of the anomeric region <2003JOC3380>. NMR characterization of iV-acetyl-L-(Y)-cysteinyl monobimane and peracetylated MSmB was also published (Section 12.10.15.4) <2002JA3492>. 

A complete NMR approach has been employed to evaluate the complexation process of catechin A with p-CD and synthetic analogues.125 The analysis of the variation of the proton chemical shifts indicated the formation of a 1 1 stoichiometric complex. 2D-ROESY provided detailed spatial information of the complex while the binding constants were obtained by using diffusion-order spectroscopy (DOSY) techniques. 

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. 

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. 

Chemical shift correlated NMR experiments are the most valuable amongst the variety of high resolution NMR techniques designed to date. In the family of homonuclear techniques, four basic experiments are applied routinely to the structure elucidation of molecules of all sizes. The first two, COSY [1, 2] and TOCSY [3, 4], provide through bond connectivity information based on the coherent (J-couplings) transfer of polarization between spins. The other two, NOESY [5] and ROESY [6] reveal proximity of spins in space by making use of the incoherent polarization transfer (nuclear Overhauser effect, NOE). These two different polarization transfer mechanisms can be looked at as two complementary vehicles which allow us to move from one proton atom of a molecule to another proton atom this is the essence of a structure determination by the H NMR spectroscopy. 

ROESY rotahonal frame nuclear overhauser effect spectroscopy... 

The structures of the compounds were elucidated by a combination of NMR techniques (lH-, 13C-, and 13C-DEPT NMR) and chemical transformation, enzymatic degradation, and as well as mass spectrometry, which gives information on the saccharide sequence. A more recent approach consists of an extensive use of high-resolution 2D NMR techniques, such as homonuclear and heteronuclear correlated spectroscopy (DQF-COSY, HOHAHA, HSQC, HMBC) and NOE spectroscopy (NOESY, ROESY), which now play the most important role in the structural elucidation of intact glycosides. These techniques are very sensitive and non destructive and allow easy recovery of the intact compounds for subsequent biological testing. 

A further field of application for the 2D NOESY and the 2D ROESY experiment.s are dynamic systems, where exchange processes may be recognized and may be analysed quantitatively (EXCSY-spectroscopy). 

ROESY Rotating Frame Overhauser Effect SpectroscopY... 

---