Steric effect exerted by the proline residue on the antecedent alanine residue.
Five model tetrapeptides: Ala-Ala-Ala-Ala, Pro-Ala-Ala-Ala, Ala-Pro-Ala-Ala, Ala-Ala-Pro-Ala and Ala-Ala-Ala-Pro, were synthesized and measured in D2O by 13 C-n.m.r. spectroscopy. The spectra analysis led us to the conclusion that for each model (irrespective of pD) in conformational equilibrium, the predominant conformation is the one in which side methyl of alanine preceding proline residue eclipses alanine carbonyl group. The influence of pD changes in cis-trans isomerism of Ala-Pro amide bond was also investigated.
D000409:Alanine; D000595:Amino Acid Sequence; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009842:Oligopeptides / Q000138:chemical synthesis*; D011392:Proline; D011487:Protein Conformation; D013329:Structure-Activity Relationship
D009842:Oligopeptides; D011392:Proline; D000409:Alanine