Aromatic regions cyclic peptides

Figure 5 One-Dimensional H NMR Spectra of Cyclic p-Sheet Peptides Showing (a) the Amide and Aromatic Regions and (b) H Regions[121a a...

A third cyclic peptide studied is cvclo(D-Phe-Glv-Ala-Glv-Pro), Figure 3 compares its solid state and solution NMR spectra. Two aspects of this peptide have been studied. First, the isotropic chemical shift positions show that structure I is preferred in the solid state and both structures I and II exist in solution. The existence of a y -turn with proline as the i+1 residue in the solid state conformation is indicated by the high field position of the Pro Cg resonance. By contrast, the Pro Cg resonance position in solution supports an equillbriun between structures I and II, since it occurs midway between an unperturbed Pro and one in a y -turn. Second, a striking feature of the solid state C spectrum of this peptide is in the aromatic region where a broad ill-defined resonance in the base line is all that is seen for the 6 and e carbons while theY... 

Figure 5. Aromatic regions of >NMR spectra of cyclic peptides containing phenylalanine. K.ey. A, expansion of Figure 3 and B, expansion of Figure 1.

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