V. Dupont et al., CONFORMATIONAL PERTURBATIONS INDUCED BY N-AMINATION AND N-HYDROXYLATION OF PEPTIDES, Journal of the American Chemical Society, 115(20), 1993, pp. 8898-8906
Amination and hydroxylation of the amide nitrogen in a peptide chain h
ave little influence on the local geometry, but both affect the hydrog
en-bonding network, and therefore the conformational properties of the
modified peptide. An experimental study in solution (IR spectroscopy
and H-1-NMR) and in the solid state (X-ray diffraction) has been carri
ed out on the N-amino and N-hydroxy analogues of the two RCO-Pro-NHMe
and RCO-Pro-Gly-NHiPr peptides known to adopt preferentially the gamma
- and beta-turn structures, respectively. The N-amino group is a weak
proton donor which does not interact significantly with the peptide ch
ain. On the contrary, the N-hydroxyl group is a strong proton donor gi
ving close contacts with the peptide carbonyls. The resulting folded c
onformers of an expanded gamma- or beta-like type, presenting an 8- or
11-membered cycle instead of a 7- or 10-membered cycle in the cognate
peptides have been also analyzed by a SYBYL molecular dynamics simula
tion.