RESUMO
The solution conformation of a designed tetradecapeptide Boc-Val-Ala-Leu-Dpg-Val-Ala-Leu-Val-Ala-Leu-Dpg-Val-Ala-Leu-OMe (Dpg-14) containing two di-n-propyl glycine (Dpg) residues has been investigated by (1)H NMR and circular dichroism in organic solvents. The peptide aggregates formed at a concentration of 3 mM in the apolar solvent CDCl(3) were broken by the addition of 12% v/v of the more polar solvent DMSO-d(6). Successive N(i)H <--> N(i+1)H NOEs observed over the entire length of the sequence in this solvent mixture together with the observation of several characteristic medium-range NOEs support a major population of continuous helical conformations for Dpg-14. Majority of the observed coupling constants (3)JNHC(alpha)H) also support phi values in the helical conformation. Circular dichroism spectra recorded in methanol and propan-2-ol give further support in favor of helical conformation for Dpg-14 and the stability of the helix at higher temperature.
