Fig. 7. NMR data reveal exchange processes between the four conformational sates of Cryst-2 in DMSO-d6 solution and cis–trans isomerization of Dab2–Pip3 peptide bond. (A) The fragment of 2D 1H,1H-NOESY spectrum (tm = 400 ms). The assignment of 1Hα resonances of the Pip3 residue in the a, b, c, and d conformers is shown. The exchange originated (inter-conformer) cross-peaks are marked by crosses. The unassigned resonances probably belong to additional structural states of Cryst-2 or to impurities. (B) Fragment of 2D 1H,13C-HSQC spectrum of Cryst-2. Signals of CH2 groups are connected by dotted lines. The assignment of HCε resonances of Pip3 residue is shown. Characteristic upfield shift of 13Cε resonance in the conformer c confirmed that the corresponding Dab2–Pip3 peptide bond is in the cis configuration. According to chemical shift data, the other conformers (a, b, d) of Cryst-2 have trans Dab2–Pip3 bonds.
