Category: M. Amblard

Site-specific grafting on titanium surfaces with hybrid temporin antibacterial peptides

J. Mater. Chem. B, 2018,6, 1782-1790. doi 10.1039/C8TB00051D


Relying on a membrane-disturbing mechanism of action and not on any intracellular target, antimicrobial peptides (AMP) are attractive compounds to be grafted on the surface of implantable materials such as silicone catheters or titanium surgical implants. AMP sequences often display numerous reactive functions (e.g. amine, carboxylic acid) on their side chains and straightforward conjugation chemistries could lead to uncontrolled covalent grafting, random orientation, and non-homogenous density. To achieve an easy and site specific covalent attachment of unprotected peptides on titanium surfaces, we designed hybrid silylated biomolecules based on the temporin-SHa amphipathic helical antimicrobial sequence. With the grafting reaction being chemoselective, we designed five analogues displaying the silane anchoring function at the N-ter, C-ter or at different positions inside the sequence to get an accurate control of the orientation. Grafting density calculations were performed by XPS and the influence of the orientation of the peptide on the surface was clearly demonstrated by the measure of antimicrobial activity. Temporin amphipathic helices are described to permeabilize the bacterial membrane by interacting in a parallel orientation with it. Our results move in the direction of this mechanism as the selective grafting of hybrid temporin 2 through a lysine placed at the center of the peptide sequence, resulted in better biofilm growth inhibition of E. coli and S. epidermis than substrates in which temporins were grafted via their C- or N-terminus.

Indoloazepinone-Constrained Oligomers as Cell-Penetrating and Blood-Brain Barrier Permeable Compounds

Chembiochem. 2018 Jan 29. doi: 10.1002/cbic.201700678. [Epub ahead of print]

Van der Poorten O, Legrand B, Vezenkov L, Garcia-Pindado J, Bettache N, Knuhtsen A, Sejer Pedersen D, Sanchez-Navarro M, Martinez J, Teixido M, Garcia M, Tourwe D, Amblard M, Ballet S.


Non-cationic and amphipathic indoloazepinone-constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [L-Aia-Xxx]n oligomers were investigated using circular dichroism and NMR spectroscopy. While Boc-[L-Aia-Gly]2,4-OBn 12-13 and Boc-[L-Aia-β3-h-L-Ala]2,4-OBn 16-17 oligomers were totally or partially disordered, Boc-[L-Aia-L-Ala]2-OBn 14 induced a typical turn stabilized by C5- and C7-membered H-bond pseudo-cycles and aromatic interactions. Boc-[L-Aia-L-Ala]4-OBn 15 exhibited a unique structure with remarkable T-shaped pie-stacking interactions involving the indole rings of the four L-Aia residues forming a dense hydrophobic cluster. All the proposed FITC-6-Ahx-[L-Aia-Xxx]4-NH2 oligomers 19-23, with exception of FITC-6-Ahx-[L-Aia-Gly]4-NH2 oligomer 18, were internalized by MDA-MB-231 cells with higher efficiency than the positive references penetratin and Arg8. In parallel, this series of compounds was successfully explored on an in vitro blood-brain barrier (BBB) permeation assay. While no passive diffusion permeability was observed for any of the tested Ac-[L-Aia-Xxx]4-NH2 oligomers in the PAMPA model, Ac-[L-Aia-L-Arg]4-NH2 26 showed significant permeation in the in vitro cell-based human model of the BBB, suggesting an active mechanism of cell-penetration.

C9/12 Ribbon-Like Structures in Hybrid Peptides Alternating α- and Thiazole-Based γ-Amino Acids

Chemistry. 2017 Dec 11;23(69):17584-17591. doi: 10.1002/chem.201704001. Epub 2017 Nov 15.

Bonnel C, Legrand B, Simon M, Martinez J, Bantignies JL, Kang YK, Wenger E, Hoh F, Masurier N, Maillard LT.


According to their restricted conformational freedom, heterocyclic γ-amino acids are usually considered to be related to Z-vinylogous γ-amino acids. In this context, oligomers alternating α-amino acids and thiazole-based γ-amino acids (ATCs) were expected to fold into a canonical 12-helical shape as described for α/γ-hybrid peptides composed of cis-α/β-unsaturated γ-amino acids. However, through a combination of X-ray crystallography, NMR spectroscopy, FTIR experiments, and DFT calculations, it was determined that the folding behavior of ATC-containing hybrid peptides is much more complex. The homochiral α/(S)-ATC sequences were unable to adopt a stable conformation, whereas the heterochiral α/(R)-ATC peptides displayed novel ribbon structures stabilized by unusual C9/12 -bifurcated hydrogen bonds. These ribbon structures could be considered as a succession of pre-organized γ/α dipeptides and may provide the basis for designing original α-helix mimics.

Ribbon-like Foldamers for Cellular Uptake and Drug Delivery

Chembiochem 2017 Nov 2;18(21):2110-2114. doi: 10.1002/cbic.201700455. Epub 2017 Sep 22.

Vezenkov LL, Martin V, Bettache N, Simon M, Messerschmitt A, Legrand B, Bantignies JL, Subra G, Maynadier M, Bellet V, Garcia M, Martinez J, Amblard M.


Different intracellular delivery systems of bioactive compounds have been developed, including cell-penetrating peptides. Although usually nontoxic and biocompatible, these vectors share some of the general drawbacks of peptides, notably low bioavailability and susceptibility to protease degradation, that limit their use. Herein, the conversion of short peptide sequences into poly-α-amino-γ-lactam foldamers that adopt a ribbon-like structure is investigated. This template is used to distribute critical cationic and/or hydrophobic groups on both sides of the backbone, leading to potent short, cell-permeable foldamers with a low positive-charge content. The lead compound showed dramatically improved protease resistance and was able to efficiently deliver a biologically relevant cargo inside cells. This study provided a simple strategy to convert short peptide sequences into efficient protease-resistant cell-penetrating foldamers.

Structure-Activity Relationships of JMV4463, a Vectorized Cathepsin D Inhibitor with Antiproliferative Properties: The Unique Role of the AMPA-Based Vector

ChemMedChem, 2016, Volume: 11, Issue: 3, Pages: 302-308, DOI: 10.1002/cmdc.201500457

L. Vezenkov, C. A. Sanchez, V. Bellet, V. Martin, M. Maynadier, N. Bettache, V. Lisowski, J. Martinez, M. Garcia, M. Amblard, J. F. Hernandez


Cathepsin D (CathD) is overexpressed and secreted by several solid tumors and stimulates their growth, the mechanism of which is still not understood.  In this context, the pepstatin bioconjugate JMV4463 [Ac-arg-O2Oc-(Val)3-Sta-Ala-Sta-(AMPA)4-NH2; O2Oc=8-amino-3,6-dioxaoctanoyl, Sta=statine, AMPA=ortho-aminomethylphenylacetyl], contg. a new kind of cell-penetrating vector, was previously shown to exhibit potent antiproliferative effects in vitro and to delay the onset of tumors in vivo.  In this study, the authors performed a structure-activity relationship anal. to evaluate the significance of the inhibitor and vector moieties of JMV4463.  By modifying both statine residues of pepstatin the authors found that the antiproliferative activity is correlated with CathD inhibition, supporting a major role of the catalytic activity of intracellular CathD in cancer cell proliferation.  Replacing the vector composed of four AMPA units with other vectors was found to abolish cytotoxicity, although all of the conjugates enabled pepstatin transport into cells.  In addn., the AMPA4 vector must be localized at the C terminus of the bioconjugate.  The unexpected importance of the vector structure and position for cytotoxic action suggests that AMPA4 enables pepstatin to inhibit the proteolysis of crit. CathD substrates involved in cell proliferation via a unique mechanism of action.

Unambiguous and Controlled One-Pot Synthesis of Multifunctional Silica Nanoparticles

Chemistry of Materials, 2016, Volume: 28, Issue: 3, Pages: 885-889, DOI: 10.1021/acs.chemmater.5b04398

J. Ciccione, T. Jia, J .L. Coll, K. Parra, M. Amblard, S. Jebors, J. Martinez, A. Mehdi, G. Subra 


A method for obtaining in a single step well-defined tunable multifunctional fluorescent particles having their surface functionalized with multiple covalently linked ligands is reported.  The strategy relies on the synthesis of hybrid bioorg.-inorg. peptide ligands, greatly simplifying the design of multifunctional nanoparticles.  It was possible to tune the ratio of two grafted ligands on the surface of the SiNPs simply by adjusting the relative concn. of hybrid species in the starting soln.  An original fluorine NMR method was applied to the dissolved SiNPs to demonstrate our hypothesis.

A switchable stapled peptide

Journal of Peptide Science, 2016, Volume: 22, Issue: 3, Pages: 143-148, DOI: 10.1002/psc.2851

A. Kalistratova, B. Legrand, P. Verdie, E. Naydenova, M. Amblard, J. Martinez, G. Subra


The O-N acyl transfer reaction has gained significant popularity in peptide and medicinal chem.  This reaction has been successfully applied to the synthesis of difficult sequence-contg. peptides, cyclic peptides, epimerization-free fragment coupling and more recently, to switchable peptide polymers.  Herein, we describe a related strategy to facilitate the synthesis and purifn. of a hydrophobic stapled peptide.  The staple consists of a serine linked through an amide bond formed from its carboxylic acid function and the side chain amino group of diaminopropionic acid and through an ester bond formed from its amino group and the side chain carboxylic acid function of aspartic acid.  The α-amino group of serine was protonated during purifn.  Interestingly, when the peptide was placed at physiol. pH, the free amino group initiated the O-N shift reducing the staple length by one atom, leading to a more hydrophobic stapled peptide.

Selective homodimerization of unprotected peptides using hybrid hydroxydimethylsilane derivatives

RSC Advances, 2016, Volume: 6, Issue: 39, Pages: 32905-32914, DOI: 10.1039/C6RA06075G

C. Echalier, A. Kalistratova, J. Ciccione, A. Lebrun, B. Legrand, E. Naydenova, D. Gagne, J. A. Fehrentz , J. Marie, M. Amblard, A. Mehdi, J. Martinez, G. Subra 


We developed a simple and straightforward way to dimerize unprotected peptide sequences that relies on a chemoselective condensation of hybrid peptides bearing a hydroxydimethylsilyl group at a chosen position (either C-ter, N-ter or side-chain linked) to generate siloxane bonds upon freeze-drying. Interestingly, the siloxane bond sensitivity to hydrolysis is strongly pH-dependent. Thus, we investigated the stability of siloxane dimers in different exptl. conditions. For that purpose, 29Si, 13C and 1H NMR spectra were recorded to accurately quantify the ratio of dimer/monomer. More interestingly, we showed that 1H resonances of the methylene and Me groups connected to the Si can be used as sensitive probes to monitor siloxane hydrolysis and to det. the half-lives of the dimers. Importantly, we showed that the dimers were rather stable at pH 7.4 (t1/2 ≈ 400 h) and we applied the dimerization strategy to bioactive sequences. Once optimized, three dimers of the growth hormone releasing hexapeptide (GHRP-6) were prepd. Interestingly, their pharmacol. evaluation revealed that the activity of the dimeric ligands could be switched from agonist to inverse agonist depending on the position of dimerization.

Conformationally Constrained Peptidomimetics as Inhibitors of the Protein Arginine Methyl Transferases

Chemistry – A European Journal, 2016, Volume: 22, Issue: 39, Pages: 14022-14028, DOI: 10.1002/chem.201602518

A. Knuhtsen, B. Legrand, O. Van der Poorten, M. Amblard, J. Martinez, S. Ballet, J. L. Kristensen, D. S. Pedersen 


Protein arginine N-Me transferases (PRMTs) belong to a family of enzymes that modulate the epigenetic code through modifications of histones.  In the present study, peptides emerging from a phage display screening were modified in the search for PRMT inhibitors through substitution with non-proteinogenic amino acids, N-alkylation of the peptide backbone, and incorporation of constrained dipeptide mimics.  One of the modified peptides (23) showed an increased inhibitory activity towards several PRMTs in the low μM range and the conformational preference of this peptide was investigated and compared with the original hit using CD and NMR spectroscopy.  Introducing two constrained tryptophan residue mimics (L-Aia) spaced by a single amino acid was found to induce a unique turn structure stabilized by a hydrogen bond and arom. π-stacking interaction between the two L-Aia residues.

Quantitative MALDI-MS Binding Assays: An Alternative to Radiolabeling

ChemMedChem, 2016, Volume: 11, Issue: 23, Pages: 2582-2587, DOI: 10.1002/cmdc.201600447

M. Rossato,  G. Miralles, C. M’Kadmi, M. Maingot, M. Amblard, B. Mouillac, D. Gagne, J. Martinez, G. Subra, C. Enjalbal, S. Cantel, 


Radiolabeling of ligands is still the gold std. in the study of high-affinity receptor-ligand interactions. In an effort toward safer and simpler alternatives to the use of radioisotopes, we developed a quant. and highly sensitive matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) method that relies on the use of chem. tagged ligands designed to be specifically detectable when present as traces in complex biol. mixts. such as cellular lysates. This innovative technol. allows easy, sensitive detection and accurate quantification of analytes at the sub-nanomolar level. After statistical validation, we were able to perform pharmacol. evaluations of G protein-coupled receptor (V1A-R)-ligand interactions. Both satn. and competitive binding assays were successfully processed.