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Issue 20, 2012
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Searching for new cell-penetrating agents: hybrid cyclobutane–proline γ,γ-peptides

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Two generations of hybrid γ,γ-peptides containing cyclobutane amino acids and cis-γ-amino-L-proline joined in alternation have been synthesized and their capacity to cross the eukaryotic cell membrane has been evaluated. The first generation consists of di-, tetra- and hexapeptides, and their properties have been analyzed as well as the influence of peptide length and chirality of the cyclobutane residues. Results have shown that the absolute configuration of the cyclobutane amino acid does not have a relevant influence. The second generation consists of hybrid γ,γ-hexapeptides with a common backbone and distinct side chains introduced with different linkage types through the α-amino group (Nα) of the proline monomers. These peptides have been shown to be non-toxic towards HeLa cells and to internalize them effectively, the best results being obtained for the peptides with a spacer of five carbons between the Nα atom and the guanidinium group. The introduction of cyclobutane residues inside the sequence affords a good balance between charge and hydrophobicity, reducing the number of positive charges. This results in lower toxicity and similar cell-uptake properties when compared to previously described peptide agents.

Graphical abstract: Searching for new cell-penetrating agents: hybrid cyclobutane–proline γ,γ-peptides

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The article was received on 30 Jan 2012, accepted on 02 Apr 2012 and first published on 02 Apr 2012

Article type: Paper
DOI: 10.1039/C2OB25220A
Org. Biomol. Chem., 2012,10, 4050-4057

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    Searching for new cell-penetrating agents: hybrid cyclobutaneproline γ,γ-peptides

    E. Gorrea, D. Carbajo, R. Gutiérrez-Abad, O. Illa, V. Branchadell, M. Royo and R. M. Ortuño, Org. Biomol. Chem., 2012, 10, 4050
    DOI: 10.1039/C2OB25220A

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