Conformation and chiral effects in α,β,α-tripeptides

Short α,β,α-tripeptides comprising a central chiral trisubstituted β 2,2,3*-amino acid residue form unusual γ-turns and δ-turns in CDCl 3 and DMSO-d 6 solutions but do not form β-turns. Thermal coefficients of backbone amide protons, 2D-NMR spectra, and molecular modeling revealed that these motifs were strongly dependent on the configuration (chiral effect) of the central β-amino acid residue within the triad. Accordingly, SSS tripeptides adopted an intraresidual γ-turn like (C6) arrangement in the central β-amino acid, whereas SRS diastereomers preferred an extended δ-turn (C9) conformation. A different SRS-stabilizing bias was observed in the crystal structures of the same compounds, which shared the extended δ-turn (C9) found in solution, but incorporated an additional extended β-turn (C11) to form an overlapped double turn motif.

Bibliographic Details

Main Authors:	Saavedra, Carlos J., Boto, Alicia, Hernández, Rosendo, Miranda, José Ignacio, Aizpurua, Jesús M.
Other Authors:	Ministerio de Ciencia e Innovación (España)
Format:	artículo biblioteca
Published:	American Chemical Society 2012-07-05
Subjects:	Amides, Peptides and proteins, Solvents, Conformation, Molecular structure,
Online Access:	http://hdl.handle.net/10261/199404 http://dx.doi.org/10.13039/501100004837
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