NMR NOESY

FIGURE 10. Contour plot of two-dimensional nuclear Overhauser effect ll NMR (NOESY) of the protonated Schiff base of all-traos-retinal, in chloroform, with formate as the counterion. The intermolecular NOE cross-peak observed between H15 of the retinal and the counterion proton, at a mixing time of 0.4 s, is shown. Top trace f2 projection of the 2D NOE spectrum. Reproduced by permission of John Wiley Sons from Reference 36... 

Figure 9.2 (a) Partial two-dimensional NMR (NOESY) spectrum of duplex 2 2. The inter-... 

Our results confirmed the feasibility of this strategy (Zeng et al. 2002). Peptide segments were attached to an unsymmetrical, 4-H bonded heteroduplex template with the complementary sequences of ADAA/DADD, leading to four hybrid strands 13a, 13b, 14a, and 14b. Combination of strands 13a and 13b with strands 14a and 14b resulted in four different pairs. The formation of well-defined /3-sheets by different combinations of paired peptide sequences was confirmed by 1-D and 2-D NMR, ITC, and VPO smdies. For example, 2-D NMR (NOESY) showed interstrand NOEs corresponding to protons of duplex templates and the... 

The presence of intramolecular H bonds in the cross-linked products was probed by carrying out 2-D NMR (NOESY) experiments on cross-linked 26-27, which contains two interstrand intramolecular H bonds. It was found that the same cross-strand NOEs were detected in CDCI3 (Fig. 9.18a) and in H20/THF-r(8 (80/20, v/v Fig. 9.18b). Furthermore, diluting 26-27 from 9 to 0.2 mM in the same aqueous solvent led to no shift in the two aninline NH signals, which remained at 9.75 ppm. These results suggest the persistence of an intramolecular H bonded conformation for 26-27 in aqueous media, which is consistent with the thermodynamic mechanism shown in Figure 9.17. 

The 2D-NMR NOESY correlations determined the absolute configuration (3S) for spirodioxocin 641a, which could adopt different conformations whose relative populations depended on steric factors, anomeric, and related effects and intramolecular //-bonding. In the preferred conformation of 641a, both endocyclic oxygen atoms were disposed in equatorial position relative to the other cycle and, therefore, such a structure was not stabilized by a conformational anomeric effect. The conformation (3Y)-641 a that disposed both endocyclic oxygen atoms in an axial position, which was stabilized by a double conformational anomeric effect, would imply chair-chair conformation for... 

The structures of some of these compounds have been established by proton and carbon-13 spectroscopy <83JA5390>. In some cases nuclear Overhauser effect (NOE) <85T603> or NMR (NOESY) experiments <94CC1383> have been used. 

Binding or association constants in principle can be obtained by any spectroscopic method, which permits the analysis of solutions, i.e., H NMR (Chapter 9), UV-Vis and fluorescence spectra (Section 10.3), and CD, and also by microcalorimetric methods (Chapter 8), potentiometric titrations (Section 10.5), etc. [5,10]. Information about the supramolecular structure in solution, on the other hand, only can be gained by NMR (NOESY or ROESY) or CD spectroscopy - preferably in combination with computational methods [11-17] (see, however, Chapter 11, which details the limitations of CyD modeling). 

Figure 9.9. Two-dimensional NMR (NOESY and the Model Protein v, (GVGVP GVGFP GEGFP HOHAHA) proton spectroscopy at 600MHz allows GVGVP GVGFP GFGFPU, as listed in Table 5.5. for determination of purity and verification of the (Reproduced with permission from Urry et al. ) basic 30 residue, 6 pentamer, repeating sequence of...

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