Issue 12, 2012

Novel peptide foldameric motifs: a step forward in our understanding of the fully-extended conformation/310-helix coexistence

Abstract

The fully-extended, multiple C5, conformation or 2.05 helix is a very appealing peptide secondary structure, in particular for its potential use as a molecular spacer, as it is characterized by the longest elevation (as high as 3.62 Å) between the α-carbon atoms of two consecutive α-amino acids. Despite this intriguing property, however, it is only poorly investigated and understood. Here, using a complete series of Cα,α-diethylglycine (Deg) homo-oligopeptide esters to the pentamer level, we exploited the properties of a fluorophore and a quencher, synthetically positioned at the N- and C-termini of the main chain, respectively, to check the applicability of the fully-extended conformation as a rigid molecular spacer. The fluorescence study was complemented by FT-IR absorption and NMR conformational investigations. The X-ray diffraction structures of selected compounds are also reported. Unfortunately, we find that, even in a solvent of low polarity, such as chloroform, in this peptide series an equilibrium does take place between the fragile fully-extended conformation and the 310-helical structure, the latter becoming more and more stable as the main chain is elongated. Since the Deg homo-peptide esters lacking any terminal aromatic group, previously investigated, are known to adopt a stable fully-extended conformation in chloroform solution, we tend to attribute the 3D-structure instability observed in this work to the presence of multiple aromatic rings in their blocking groups.

Graphical abstract: Novel peptide foldameric motifs: a step forward in our understanding of the fully-extended conformation/310-helix coexistence

Supplementary files

Article information

Article type
Paper
Submitted
04 Nov 2011
Accepted
02 Feb 2012
First published
14 Feb 2012

Org. Biomol. Chem., 2012,10, 2413-2421

Novel peptide foldameric motifs: a step forward in our understanding of the fully-extended conformation/310-helix coexistence

F. Formaggio, M. Crisma, G. Ballano, C. Peggion, M. Venanzi and C. Toniolo, Org. Biomol. Chem., 2012, 10, 2413 DOI: 10.1039/C2OB06863J

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