AUTHOR=Mantsyzov Alexey B. , Savelyev Oleg Y. , Ivantcova Polina M. , Bräse Stefan , Kudryavtsev Konstantin V. , Polshakov Vladimir I. TITLE=Theoretical and NMR Conformational Studies of β-Proline Oligopeptides With Alternating Chirality of Pyrrolidine Units JOURNAL=Frontiers in Chemistry VOLUME=6 YEAR=2018 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2018.00091 DOI=10.3389/fchem.2018.00091 ISSN=2296-2646 ABSTRACT=

Synthetic β-peptides are potential functional mimetics of native α-proteins. A recently developed, novel, synthetic approach provides an effective route to the broad group of β-proline oligomers with alternating patterns of stereogenic centers. Conformation of the pyrrolidine ring, Z/E isomerism of β-peptide bonds, and hindered rotation of the neighboring monomers determine the spatial structure of this group of β-proline oligopeptides. Preferences in their structural organization and corresponding thermodynamic properties are determined by NMR spectroscopy, restrained molecular dynamics and quantum mechanics. The studied β-proline oligopeptides exist in dimethyl sulfoxide solution in a limited number of conformers, with compatible energy of formation and different spatial organization. In the β-proline tetrapeptide with alternating chirality of composing pyrrolidine units, one of three peptide bonds may exist in an E configuration. For the alternating β-proline pentapeptide, the presence of an E configuration for at least of one β-peptide bond is mandatory. In this case, three peptide bonds synchronously change their configurations. Larger polypeptides may only exist in the presence of several E configurations of β-peptide bonds forming a wave-like extended structure.