No description available.

La plupart des bactéries vivent en communautés organisées, appelées biofilms, augmentant leur résistance aux traitements antibiotiques. Ainsi, la formation de biofilms sur les organes et matériels médicaux est considérée comme la cause de la majorité des infections bactériennes. Il est alors important de trouver des traitements pour empêcher ou perturber la formation de ces biofilms. Il a été proposé que les porines de P. Stuartii, Omp-Pst1 et Omp-Pst2, peuvent s’auto-assembler via un steric-zipper, étape responsable du développement initial du biofilm. Ainsi, notre objectif est de synthétiser des inhibiteurs d’interactions entre porines pour limiter ce contact intercellulaire. Nous avons développé des molécules peptidomimétiques basées sur la séquence LGNYR, active dans les deux porines. Pour cela, des réactions de chimie click sur phase solide ont été mises en oeuvre afin de synthétiser des analogues de cette séquence, comme la CuAAC pour introduire un motif triazole, dans une position variable au sein du peptide. Nous avons ainsi développé une méthode rapide et efficace afin de réaliser cette réaction par l’utilisation d’un catalyseur cuivre(I)-N-hétérocyclique carbène stable à l’air. Similairement, de nouvelles conditions ont aussi été mises au point en phase solide afin d’obtenir régiosélectivement des peptides comportant un motif isoxazole 3,4- ou 3,5-disubstitué, par la réaction entre un alcyne et un oxyde de nitrile. Ces cycloadditions 1,3-dipolaires nous ont ainsi permis d’obtenir une première librairie de peptidotriazoles et de peptidoisoxazoles. Il sera enfin possible d’étudier les biofilms grâce à la synthèse de sondes fluorescentes basées sur les inhibiteurs montrant de fortes affinités avec la cible, couplées à un fluorophore dérivé de coumarine. / In the environment, most of bacteria live as organized communities, known as biofilms, enhancing their resistance to antibiotic treatments. Thus the formation of biofilms on organ and indwelling medical devices is considered to cause the majority of bacterial infections in the human body. Thus, to enhance antibiotics efficacy, there is a high need to find treatments to prevent or disrupt biofilm formation. It has been proposed that P. stuartii porins, Omp-Pst1 and Omp-Pst2, can self-associate through a steric zipper, being responsible for the initial development of biofilms. Thus, our objective is to synthesize porin’s self-matching interactions (PSMI) inhibitors to counterfeit this intercellular contact. We developed peptidomimetic molecules based on the LGNYR sequence, that have shown to be active in both porins. Then we used click chemistry to synthesize on solid phase analogues of this sequence, as the solid phase Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) to introduce a triazole moiety into the peptide chain at different positions. We thus developed a fast and efficient method to perform this reaction using a stable copper(I)-N-heterocyclic carbene catalyst. Similarly, new conditions were developed on solid phase to synthesize regioselectively peptides containing a 3,4- or 3,5-disubstituted isoxazole moiety, through the reaction between an alkyne and a nitrile oxide. These 1,3-dipolar cycloadditions allowed us to developed a first library of peptidotriazoles and peptidoisoxazoles. We also obtained fluorescent probes based on the inhibitors showing higher affinity for the target as tools to study biofilm formation.

The overall thrust of this dissertation is to gain a comprehensive understanding over the factors that govern the performance and behavior of ultra-thin, cross-linked polymer films. Poly(NIPAAm) was used as a model polymer to study volume phase transition in surface tethered networks. Poly(NIPAAm) undergoes a reversible phase transition at approximately 32°C between a swollen hydrophilic random coil to a collapsed hydrophobic globule state, thought to be caused by increased hydrophobic attractions between the isopropyl groups at elevated temperatures. We present a simple photochemical technique for fabricating structured polymer networks, enabling the construction of responsive surfaces with unique properties. The approach is based on the photo-cross-linking of copolymers synthesized from N-isopropylacrylamide and methacroyloxybenzophenone (MaBP). In order correlate layer swelling to the MaBP content, we have studied the swelling behavior of such layers in contact with aqueous solutions with neutron reflection. The cross-linked networks provide a three-dimensional scaffold to host a variety of functionalities. These networks serve as a platform which can be used to amplify small local perturbations induced by various stimuli like temperature, pH, solvent, ionic strength and peptide modified hydrogels to bring about a macroscopic change. Neutron reflection experiments have shown that the volume-phase transition of a surface-tethered, cross-linked poly(NIPAAm) network coincided with the two-phase region of uncross-linked poly(NIPAAm) in solution. Parallel measurements with ATR-FTIR investigating the effect of temperature, pH and salts suggest that the discontinuous transition is the result of cooperative dehydration of the isopropyl groups, with water remaining confined between amide groups in the collapsed state as weakly hydrogen bonded bridges. Hybrid polymers with specific peptide sequences have shown specific response to external cues such as pH and metal ions exhibiting unique phase behavior.

Insulin and insulin-like growth factors (IGF-1 and -2) together with their receptors take part in a complex system, which affects both basal metabolism of carbohydrates, lipids and proteins as well as cell growth, proliferation, differentiation and apoptosis. Defects in action of insulin or IGFs can lead to serious diseases such as diabetes or cancer. Both of these disorders represent nowadays one of the biggest health threats to the world's population. Insulin and IGFs induce different biological effects through their cognate receptors; two isoforms of the insulin receptor (IR-A and IR-B) and the receptor for IGF-1 (IGF-1R). These receptors bind insulin and IGFs with different affinities and induce different but partially overlapping signalling events leading towards metabolic (especially insulin) or mitogenic responses (IGFs and insulin). To understand the mechanism of action of insulin and IGFs it is important to specify which structural domains of these hormones are responsible for binding to the receptors and exerting specific effects. One region that is missing in insulin is the D-domain of IGF-1 and -2. For this reason, we decided to prepare insulin analogues with the A-chain extended by either the whole D-domain of IGF-1 or IGF-2, or by fragments of the IGF-1 D-domain in order to define the...

<p>Pathogenic bacteria are evolving to drug resistant strains at alarming rates. The threat posed by drug resistant bacterial infections emphasize the need to establish new antimicrobial agents. Of immediate concern regarding the dangers of antibiotic resistance is the existence of intracellular bacteria, which find refuge from bactericidal devices by hiding within mammalian cells. Unfortunately, many therapeutics, such as vancomycin, do not possess membrane penetrating abilities to achieve efficacious eradication of bacteria at the subcellular level, allowing infections to persist. In an effort to target pathogens that thrive within mammalian cells, features of cell penetrating peptides (CPPs) and antimicrobial peptides (AMPs) were combined to develop a dual action antimicrobial CPP, cationic amphiphilic polyproline helices (CAPHs). CAPHs have proven to be an effective antimicrobial agent to combat an array of both Gram negative and Gram positive bacteria. </p> <p> </p> <p>Herein, to improve CAPHs activity, we have demonstrated how the incorporation of strategic modifications has resulted in increased cell uptake, alternative subcellular locations for CAPHs, and advanced antimicrobial potency. By simultaneously extending the helical length of CAPHs while incorporating different hydrophobic groups in place of the original isobutyl moiety that compose CAPHs we have created a <b>FL-P17-5R </b>series of peptides with five carbon aliphatic motifs: <b>Fl-P17-5B</b>, <b>Fl-P17-5C</b> and <b>Fl-P17-5L. </b>Through these modifications the peptides proved to be 2 to 5-fold more efficient in accumulating in macrophage cells than parent peptide Fl-P14LRR and where able to clear intracellular pathogenic bacteria, such as <i>Listeria</i>, from infected macrophages by 26 to 54%. </p> <p> </p> <p>In addition to making the <b>Fl-P17-5R</b> series of CAPHs to potentiate CAPHs activity, modifications to the cationic moiety of CAPHs were explored. By incorporating a new cationic monomer into the CAPHs sequence, a guanylated amino proline (GAP) residue, we produced <b>Fl-P14GAP</b>, a CAPHs peptide with an organized cationic charge display. This modification resulted in a 5-fold increase in cell uptake and a 2 to 16-fold decrease in minimum inhibitory concentration (MIC) values against strains of enteric and ESKAPE pathogens in comparison to Fl-P14LRR. <b>Fl-P14GAP</b> also executed superior clearance of intracellular pathogenic bacteria that resulted in the complete eradication of a drug resistant strain of <i>A. baumannii</i> from infected macrophage cells. Overall, our efforts with the <b>Fl-P17-5R</b> series of CAPHs and <b>Fl-P14GAP</b> have strengthened the therapeutic potential of CAPHs in the hopes of addressing the need for novel antibiotics with the propensity to eradicate intracellular pathogens.</p>

L'utilisation de peptides en tant qu'agents thérapeutiques est une stratégie très répandue dans le domaine médical, en partie grâce aux propriétés pharmacologiques conférées par leurs structures tridimensionnelles. Des méthodes de fabrication de peptides rentables et respectueuses de l'environnement sont souhaitées pour répondre aux demandes du marché thérapeutique. Les azapeptides sont des analogues peptidiques dans lesquels un ou plusieurs atomes de carbone en α (α-C) d’un acide aminé sont substitués par un azote. Ils offrent des propriétés physicochimiques différentes qui augmentent le potentiel thérapeutique de peptides. La synthèse chimique peptidique traditionnelle se déroule du sens C-terminal vers Nterminal. Cette approche nécessite une utilisation importante de groupes protecteurs et de réactifs de condensation, ce qui crée des charges environnementales dues aux déchets chimiques. En outre, les peptides naturels biologiquement actifs présentent souvent une modification au niveau du C-terminal, ce qui rend ce type de modifications difficiles dans le sens classique de synthèse. Leurs synthèses dans le sens inverse peut surmonter ces limitations. Cependant, peu de travaux ont exploré la synthèse peptidique du côté N-terminal vers le côté Cterminal, en raison des épimérisations observées durant l’élongation peptidique. Dans ce mémoire nous démontrons le développement d’une nouvelle méthode pour la synthèse d’azapeptides du côté N-terminal vers le côté C-terminal sur support solide. Nous avons exploré deux voies de synthèses qui reposent sur l’incorporation d’un espaceur entre le support solide et le peptide. L’approche utilisée pour l’élongation peptidique se fera via l’hydrazinolyse du C-terminal protégé, suivie par une activation du couplage peptidique par un intermédiaire acyle d’azoture. L’hydrazinolyse servira également à l’incorporation du motif hydrazine au sein du squelette peptidique pour générer le motif azapeptide. En utilisant la méthionine comme initiateur de la synthèse peptidique, ces travaux ont démontré qu’il est possible de récupérer l’azapeptide synthétisé en utilisant la méthode de clivage de résine via le bromure de cyanogène. / The use of peptides as therapeutic agents is a widespread strategy in the medicinal field, in part due to pharmacological properties conferred by their three-dimensional structures. Costeffective and environmentally friendly peptide manufacturing methods are desired to address therapeutic market demands. Replacement of one or more of the alpha-carbon centers of the amino acid residues in a peptide by a nitrogen yields an azapeptide analog. This substitution may enhance peptide activity and selectivity. Azapeptides can also exhibit prolonged duration of action and increased metabolic stability. Traditional peptide synthesis uses C-terminal to N-terminal elongation. This approach requires significant use of protecting groups and condensation reagents, creating environmental burdens from chemical waste. In addition, biologically active natural peptides often feature a Cterminal modification, making this type of modification difficult to achieve using the classical sense of synthesis. To overcome these challenges, the concept of inverse chemical synthesis has been considered as an alternative for peptide production. However, its adoption has faced hurdles due in part to epimerization. In this study, we explore azapeptide synthesis in the N- to C-direction. Linker strategies were studied for azapeptide elongation in the inverse direction. Two pathways were explored using a spacer strategy between the solid support and the peptide to be elongated. The approach relies on peptide elongation by hydrazinolysis of C-terminal esters, activation and coupling via acyl azides. Hydrazinolysis is also used to incorporate the aza-motif into the peptide backbone. Using methionine as a precursor for azapeptide synthesis, this work demonstrated peptide cleavage using cyanogen bromide.

No description available.

Obwohl die methodische Entwicklung der Peptidsynthese gewöhnlich eine automatisierte Herstellung erlaubt, sind für die Herstellung einer Reihe von Peptiden auch gegenwärtig Grenzen gesetzt. Einerseits kann eine im Verlauf der Kettenverlängerung auftretende Bildung intra- und /oder intermolekularer Wasserstoffbrücken zu einer begrenzten Solvatation und damit Zugänglichkeit der zu acylierenden Aminokomponente am Syntheseharz führen, andererseits kommt es beim Einbau sterisch anspruchsvoller Aminosäuren zu ungenügenden Acylierungsausbeuten. Urethangeschützte Aminosäurefluoride haben sich für den Einbau von alpha, alpha-Dialkylaminosäuren als geeignet erwiesen. Die reaktiveren urethangeschützten Aminosäurechloride sind zwar herstellbar, besitzen aber in Gegenwart einer Hilfsbase, die zum Abfangen der während ihrer Reaktion gebildeten HCl notwendig ist, eine zu geringe Stabilität (Oxazolonbildung, Abspaltung der Schutzgruppen). Erst die Verwendung von N(alpha)-Schutzgruppen, die keinen reaktionsfähigen Carbonylkohlenstoff enthalten, wie Arensulfonyl- Schutzgruppen, ermöglichen die volle Ausschöpfung der hohen Reaktivität der Aminosäurechloride. Mit Hilfe dieser Schutzgruppen gelang ein erster Vergleich der Reaktivität der Aminosäurechloride und -fluoride. Bei den durchgeführten Reaktionen wurde keine Stereomutation beobachtet. Unter Verwendung von Arensulfonylschutzgruppen war es erstmals möglich, zwei aufeinanderfolgende N-Alkyl-alpha, alpha-dialkylaminosäuren in Peptide einzubauen. Weiterhin konnten wir zeigen, daß derart geschützte Aminosäuren sich für in situ Aktivierungen mit Thionylchlorid eignen. Als Fänger für überschüssiges Aktivierungsreagenz wurden tertiäre Alkohole bzw. Amine eingesetzt. Arensulfonyl-geschützte Aminosäurechloride haben wir darüber hinaus erfolgreich in der Festphasenpeptidsynthese verwendet. In Kombination von Arensylfonyl-Schutz mit der Standard-Fmoc-Strategie gelang die Synthese eines biologisch aktiven Analogen des CRF, eines 41-mer Peptides mit einer eingefügten Tetrapeptidsequenz -Ala-MeAib-MeAib-Aib-. / Despite its wide field of application automatic peptide synthesis is still limited in certain cases. One of the limiting factors is the possibility of intra- or intermolecular hydrogen bond formation during the elongation of the peptide chain. This causes decreased solvation and thus reduced accessibility to the resin-bound amino component. Another limitation is the incorporation of sterically hindered amino acids that usually give rise to insufficient yields of acylation. Urethane protected amino acid fluorides have been shown suitable for the incorporation of alpha,alpha-dialkyl amino acids. Though the more reactive urethane protected amino acid chlorides can be readily synthesized, they do not possess the necessary stability in the presence of an auxiliary base that must be used for trapping of the hydrochloric acid formed during the reaction. Formation of oxazolons and deprotection of formerly protected functional groups would occur. Only the advent of protecting groups for the amino acid N-alpha that do not have a reactive carbonyl function - like arene sulfonyl groups - allowed to take full advantage of the high reactivity of the amino acid chlorides. These protecting groups enabled us to compare the reactivities of amino acid chlorides and fluorides for the first time. We didn't observe any stereo mutation in our experiments. The use of arene sulfonyl protecting groups permitted the consecutive incorporation of two N-alkyl-alpha,alpha-dialkyl amino acids into a peptide for the first time. Furthermore we could show, that amino acids protected in this way, are suitable for in situ activation with thionyl chloride. Tertiary alcohols and amines were used as scavenger for excessive activating reagent. Arene sulfonyl protected amino acids were also successfully used in solid phase peptide synthesis. By combining this protecting concept with the standard Fmoc approach we were able to synthesize a biologically active analogue of CRF, a peptide containing 41 residues into which we inserted the tetrapeptide Ala-MeAib-MeAib-Aib.