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ROESY-TOCSY

The pioneering work in this field, a two-dimensional relayed-NOE experiment proposed by Wagner [7], was quickly followed by the appearance of several related NMR techniques [8-17]. Application of isotropic mixing during the J-transfer period yielded the 2D TOCSY-NOESY [11, 15] and NOESY-TOCSY [12, 14] experiments. When spin-lock sequences were applied to both J and NOE-transfers, the 2D TOCSY-ROESY and ROESY-TOCSY experiments [10, 16, 17] emerged. [Pg.53]

Another way of avoiding overlaps seen in two-dimensional spectra is to introduce the third dimension. This has been illustrated with the 3D NOESY-HOHAHA [21-25], 3D HOHAHA-NOESY [25-27], NOESY-COSY [28, 29], COSY-NOESY [28] and ROESY-TOCSY [23] experiments. A principal drawback, associated with homonuclear 3D techniques, is the low digital resolution achievable along the first and second spectral axes. This limitation can to certain extent be removed by implementing band selective pulses into the 3D homonuclear experiments [21, 26, 28-31]. [Pg.54]

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... [Pg.69]

In the subsequent ID ROESY-TOCSY experiment (pulse sequence of fig. 7(c)), a selective TOCSY transfer was applied from H-4c. During the... [Pg.70]

Fig. 8. ID ROESY-TOCSY. (a) H spectrum of the oligosaccharide 3 (5 mg/0.5 ml D2O). (b) ID ROESY spectrum of 3 acquired using the pulse sequence of fig. 7(a) with selective excitation of the H-lb proton. Duration of the 270° Gaussian pulse and the spin-lock pulse ( yBi/ K = 2.8 kHz) was 49.2 ms and 0.5 s, respectively. The spin-lock pulse was applied 333.3 Hz downfield from the H-lb resonance. The time used for the frequency change was 3 ms. (c) ID ROESY-TOCSY spectrum acquired using the pulse sequence of fig. 7(c) and the selective ROESY transfer from H-lb followed by a selective TOCSY transfer from H-4c. Parameters for the ROESY part were the same as in (b). A 49.2 ms Gaussian pulse was used at the beginning of the 29.07 ms TOCSY spin lock. 256 scans were accumulated. A partial structure of 3 is given in the inset. Solid and dotted lines represent TOCSY and ROESY... Fig. 8. ID ROESY-TOCSY. (a) H spectrum of the oligosaccharide 3 (5 mg/0.5 ml D2O). (b) ID ROESY spectrum of 3 acquired using the pulse sequence of fig. 7(a) with selective excitation of the H-lb proton. Duration of the 270° Gaussian pulse and the spin-lock pulse ( yBi/ K = 2.8 kHz) was 49.2 ms and 0.5 s, respectively. The spin-lock pulse was applied 333.3 Hz downfield from the H-lb resonance. The time used for the frequency change was 3 ms. (c) ID ROESY-TOCSY spectrum acquired using the pulse sequence of fig. 7(c) and the selective ROESY transfer from H-lb followed by a selective TOCSY transfer from H-4c. Parameters for the ROESY part were the same as in (b). A 49.2 ms Gaussian pulse was used at the beginning of the 29.07 ms TOCSY spin lock. 256 scans were accumulated. A partial structure of 3 is given in the inset. Solid and dotted lines represent TOCSY and ROESY...
The combination of HOHAHA transfer with cross-relaxation in the rotating frame leads to TOCSY-ROESY (TORO) or ROESY-TOCSY (ROTO) experiments (Kessler et al., 1988a Williamson et al., 1992). Two-dimensional hetero-TOCSY-NOESY experiments (Kellogg et al., 1992 Kellogg and Schweitzer, 1993), which combine heteronuclear Hartmann-Hahn transfer with a homonuclear NOESY mixing step, have been used for a P-driven assignment strategy of RNA and DNA spectra. [Pg.226]

ROESY-TOCSY experiment Selective inverse detection of C-H correlation Scalar heteronuclear recoupled interaction by multiple pulse Simulation program one Selectively inverted soft PICSY Singular value decomposition Tailored correlation spectroscopy Triple-resonance J cross-polarization Total correlation spectroscopy TOCSY-ROESY experiment TOCSY without NOESY... [Pg.241]

The assignment of structures by NMR in the highly hydrogenated skeleton is not straightforward due to the similar chemical environment of the methylene groups. In the H-NMR spectrum ((see Fig. (2)) the upfield region (0.5-4 ppm) is severely congested and methods that have been applied to new structure elucidation, such as HMQC (or HSQC), HMBC, INEPT, COSY, NOESY, ROESY, TOCSY (HOHAHA), HMQC-TOCSY, are needed. A particularly useful method is HMQC-TOCSY (see... [Pg.583]

The structures of the glycosylphospholipids 1 and 2 were supported by NMR spectroscopy and mass spectrometry data. The as well as P NMR spectra for compound 1 were almost identical to those for compound 2. Full structural assignment of 2 (with exception for the acyl and alkyl residues) was performed by a combination of H, COSY, ROESY, TOCSY and HSQC spectroscopy and presented in Table 1. The P NMR signals were assigned using H, P HMQC technique. The molecular masses for the GPIs 1 and 2 were confirmed by MALDI-TOF and electrospray mass spectrometry. ... [Pg.302]

ROESY TOCSY peaks of opposite sign with respect to cross-relaxation ones. Very sensitive to offset. Try different carrier frequency. [Pg.277]

Table 1 Comparison of the salient features of ROESY, TOCSY and NOESY... Table 1 Comparison of the salient features of ROESY, TOCSY and NOESY...
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) ]. [Pg.346]

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]. [Pg.215]

Whereas spin decoupling, COSY and TOCSY techniques are used to establish connectivities between protons through bonds, techniques that make use of the nuclear Overhauser effect (NOE), such as 1-D NOE and NOESY, 1- and 2-D GOESY, 1- and 2-D ROESY, can establish connectivities through space. Before looking at these techniques in detail, it s worth spending a little time considering the NOE phenomenon itself - in a nonmathematical manner, of course ... [Pg.116]

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). [Pg.123]

The stereochemistry and conformation of di-Schiff bases containing calix[4]arene unit U(IV) complexes have been deduced on the basis of the 2D TOCSY and T-ROESY measurements.116... [Pg.175]

Fig. 10.19. IDR-HSQC-TOCSY spectrum of the complex marine polyether toxin brevetoxin-2 (7). The data were recorded overnight using a 500 pg sample of the toxin (MW = 895) dissolved in 30 pi of d6-benzene. The data were recorded at 600 MHz using an instrument equipped with a Nalorac 1.7 mm SMIDG probe. Direct responses are inverted and identified by red contours relayed responses are plotted in black. The IDR-HSQC-TOCSY data shown allows large contiguous protonated segments of the brevetoxin-2 structure to be assembled, with ether linkages established from either long-range connectivities in the HMBC spectrum and/or a homonuclear ROESY spectrum. Fig. 10.19. IDR-HSQC-TOCSY spectrum of the complex marine polyether toxin brevetoxin-2 (7). The data were recorded overnight using a 500 pg sample of the toxin (MW = 895) dissolved in 30 pi of d6-benzene. The data were recorded at 600 MHz using an instrument equipped with a Nalorac 1.7 mm SMIDG probe. Direct responses are inverted and identified by red contours relayed responses are plotted in black. The IDR-HSQC-TOCSY data shown allows large contiguous protonated segments of the brevetoxin-2 structure to be assembled, with ether linkages established from either long-range connectivities in the HMBC spectrum and/or a homonuclear ROESY spectrum.
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. [Pg.53]

One-dimensional spectra obtained in these experiments can be compared to ID traces of nD NMR spectra but offering much better digital resolution and shorter acquisition times. On the negative side each trace needs to be acquired separately and thus, if several sites are to be inspected, a series of ID experiments must be performed. In practice, this exercise is preceded by careful inspection of standard two-dimensional COSY, TOCSY, NOESY or ROESY spectra and only the ambiguous assignments are tackled by combined ID techniques. [Pg.54]

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... [Pg.71]


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See also in sourсe #XX -- [ Pg.69 ]




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