Incorporation of fluorinated prolines and pseudoprolines peptide chains, conformational consequences and applications

Cette thèse porte sur la synthèse d’analogues fluorés de mimes de collagène synthétique et sur l’étude de leurs caractéristiques thermodynamiques, cinétiques et structurales. Notre laboratoire a récemment mis au point la synthèse d'acides aminés fluorés mimes de la proline (pseudoprolines). Dans un premier temps, une étude préliminaire a été effectuée sur des triplets monomériques modèles afin de confirmer l'aptitude de nos mimes fluorés à stabiliser les conformations pré-requises pour la structuration en triple hélice du collagène. Une fois celles-ci confirmées, nous avons ensuite mis au point des voies de synthèse permettant l'incorporation de ces pseudoprolines fluorées en synthèse peptidique sur phase solide. La synthèse de mime de collagène synthétique (21 résidus) incorporant nos analogues fluorés de proline a ensuite été réalisée. Les caractéristiques thermodynamiques, cinétiques et structurales de ces peptides mimes de collagène fluoré ont été déterminées par dichroïsme circulaire et par RMN. Ces pseudoprolines fluorées possèdent des propriétés singulières permettant l’obtention d’informations structurales au niveau local et peuvent ainsi être considérées comme de réelles sondes RMN 1H et 19F. Les résultats obtenus ouvrent également la voie à de nouvelles approches pour la synthèse de mimes peptidiques de collagène.In this thesis, we approach the synthesis of fluorinated analogs of collagen model peptides (CMP) and the study of their thermodynamic, kinetic and structural characteristics. Our laboratory recently developed the synthesis of fluorinated amino acids analogs of the proline residue (pseudoprolines). Firstly, a preliminary study was carried out on model triplets in order to confirm our fluorinated analogs’ ability to stabilize the pre-requisite conformations of collagen’s triple helix. Once these structural characteristics confirmed, we developed synthetic routes for the incorporation of these fluorinated pseudoprolines in solid phase peptide synthesis (SPPS). Several CMPs (21 residues) incorporating our fluorinated pseudoproline analogs were synthesized. The thermodynamic, kinetic and structural characteristics of these fluorinated CMPs were determined by circular dichroism and NMR. The fluorinated pseudoprolines possess singular properties which enable to acquire detailed insights on their structural surroundings. Thus, they can be considered as 1H and 19F NMR probes. The results obtained in this study also open the way to novel approaches for the synthesis of collagen model peptides

New insights into the structural and dynamics properties of collagen model peptides using CD spectroscopy, MD simulations and innovative NMR approaches

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Inviting Trifluoromethylated Pseudoprolines into Collagen Model Peptides

Numerous Collagen Model Peptides (CMPs) have been engineered using proline derivatives substituted at their C(3) and/or C(4) position in order to stabilize or to functionalize collagen triple helix mimics. However, no example has been reported so far with C(5) substitutions. Here, we introduce a fluorinated CMP incorporating trifluoromethyl groups at the C(5) position of pseudoproline residues. In tripeptide models, our NMR and Molecular Dynamics (MD) studies have shown that, when properly arranged, these residues meet the structural requirements for triple helix assembly. A host-guest CMP could be synthesized and its NMR analysis in solution confirmed the presence of structured homotrimers that we interpret as triple helices. MD calculations showed that the triple helix model remained stable throughout the simulation, with all six trifluoromethyl groups pointing outwards from the triple helix. Pseudoprolines substituted at the C(5) positions appeared as valuable tools for the design of new fluorinated collagen mimicking peptides