COSY spectra

One kind of 2D NMR is called COSY, which stands for correlated spectroscopy With a COSY spectrum you can determine by inspection which signals correspond to spin coupled protons Identifying coupling relationships is a valuable aid to establishing a molecule s connectivity... 

Section 13 19 2D NMR techniques are enhancements that are sometimes useful m gam mg additional structural information A H H COSY spectrum reveals which protons are spin coupled to other protons which helps m deter mining connectivity A HETCOR spectrum shows the C—H connections by correlating C and H chemical shifts... 

These signals in the NOE spectra therefore in principle make it possible to determine which fingerprint in the COSY spectrum comes from a residue adjacent to the one previously identified. For example, in the case of the lac-repressor fragment the specific Ser residue that was identified from the COSY spectrum was shown in the NOE spectrum to interact with a His residue, which in turn interacted with a Val residue. Comparison with the known amino acid sequence revealed that the tripeptide Ser-His-Val occurred only once, for residues 28-30. 

Figure 3. Fingerprint region of the COSY spectrum of RpII in H O showing the amide to a proton connectivities. Cross peaks are labeled with the identity of the amino acid in the sequence from which they arise.

Figure 5.27 Schematic diagram of a COSY spectrum illustrating how intrinsically different cross-peaks are from diagonal peaks. The circles represent the cross-peaks in an AB coupled system. The diagonal peaks have dispersion shape, and the crosspeaks have an absorption shape though they alternate in sense. The diagonal peaks are centered at d 8,i) and (8 , 8 ) the cross-peaks appear at (8., 8 ) and (8 , 8 ).

Figure 5.55 (a) Symmetrized version of a COSY spectrum in which noise lines are... 

Figure 5.36 Effect of decoupling in v, dimension on the COSY spectrum of 9-hydroxytricyclodecan-2,5-dione. The ID H-NMR spectrum on Vj is fully coupled, while along v, it is fully decoupled. The region between the dashed lines represents a band of signals associated with proton Hj and its connectivities with other protons by projection onto the Vj axis. (Reprinted from J. Magn. Reson. 44, A. Bax, el ai, 542, copyright (1981), with permission from Academic Press, Inc.)...

Figure 5.37 (a) Conventional phase-sensitive COSY spectrum of basic pancreatic trypsin inhibitor, (b) Double-quantum filtered (DQF) phase-sensitive COSY spectrum of the same trypsin inhibitor, in which singlet resonances and solvent signal are largely suppressed. Notice how clean the spectrum is, especially in the region near the diagonal line. (Reprinted from Biochem. Biophys. Res. Comm. 117, M. Ranee, et al., 479, copyright (1983) with permission from Academic Press, Inc.)... 

How are coupling constants measured from the E. COSY spectrum ... 

The COSY-45 spectrum of podophyllotoxin and its H-NMR data are shown. Assign and interpret the H/ H cross-peaks in the COSY spectrum. 

The DQF (double-quantum filtered)-COSY spectrum of an isoprenyl coumarin along with H-NMR data are shown. Determine the H/ H homonuclear interactions in the DQF-COSY spectrum. 

The hetero-COSY spectrum of vasicinone along with the H-NMR assignments and C-NMR data are shown. Assign the C-NMR chemical shifts to the various protonated carbons based on the one-bond hetero-nuclear shift correlations. 

The HMQC spectrum, H-NMR chemical shift assignments, and C-NMR data of vasicinone are shown. Consider the homonuclear correlations obtained from the COSY spectrum in Problem 5.14, and then determine the carbon framework of the spin systems. 

Figure 6.11 A 3D heteronuclear HMQC-COSY spectrum of a tripepiide. The o),-axis represents N chemical shifts, whereas the (Or and 88, copyright (1988), with permission from Academic Pre.ss, Inc.)...

The pulse sequences for HMQC-COSY and HMQC-NOESY experiments are presented in Fig. 6.10. The 3D HMQC-COSY spectrum of a N labeled tripeptide is shown in Fig. 6.11. Since the coherence transfer involved in this experiment is N([Pg.362]

Figure 7.3 One-dimensional COSYspectram for an AX system, (a) A common ID sjjectrum. (b) Selective excitation of spin A leads to a ID COSY spectrum with antiphase X lines and maximum transfer of magnetization from A to X. (Reprinted from Mag. Reson. Chem. 29, H. Kessler et at, 527, copyright (1991), with permission from John Wiley and Sons Limited, Baffins Lane, Chichester, Sussex P019 lUD, England.)...

Figure 7.25 Homoniiclear double-quantum filtered COSY spectrum (400 MHz) of 8-mMangiotensin II in H,0 recorded without phase cycling. Magnetic field gradient pulses have been used to select coherence transfer pathways. (Reprinted from J. Mag. Reson. 87, R. Hurd, 422, copyright (1990), with permission from Academic Press, Inc.)...

Figure 18. A 0.2-s delayed COSY spectrum of the aliphatic region of 10 (2mg, CDCLj). Long-range "W-type" coupling of 19 and 21 axial protons to 30-CHj and coupling across the gem dimethyls from I9eq to 21 eq establish the position of oxidation at C-22. The spectrum was obtained under conditions similar to those in Figure 1, except that 32 transients were acquired for each of 128 x 512 data point spectra (17).

The H,H COSY spectrum of model compound 1 is shown in Fig. 24. In fact you can see a total of three spectra the central square which is the actual 2D spectrum and two proton ID spectra at the top and on the left. The computer software generates this combination of spectra automatically using a previously recorded ID proton spectrum. 

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