La thérapie photo-dynamique (PDT) est une thérapeutique applicable à de nombreuses spécialités. Elle consiste en l'administration d'un photosensibilisateur qui se concentre dans un délai variable dans la lésion à traiter puis l'éclairage de la lésion (par une lumière de longueur d'onde déterminée par le spectre d'absorption du photosensibilisateur) qui conduit finalement à la destruction de la lésion [1]. Le but de mon projet d'étude est de faire l'étude et control des propriétés des membranes. nous allons utiliser des bactéries comme des membranes artificielles. Nous allons utiliser les molécules azobenzenique dans des milieux réels où il y'a des bactéries ou d'autres cellules vivantes. Des bactéries ont des impacts sur la santé humaine. plusieurs bactéries ont besoin de se déplacer vers des sites spécifiques. Le moyen de locomotion le plus commun est le moteur flagellaire. Les bactéries flagellaires ont un moteur rotatif ancré dans leur membrane qui transmet sa rotation à un long filament en forme d'hélice se trouvant à l'extérieur de la bactérie via un joint universel se nommant le crochet. De plus, les moteurs flagellaires jouent un rôle très important durant les infections bactériennes. En effet, les bactéries se déplacent souvent dans des milieux anisotropes, où les propriétés physiques dépendent de la direction. La motilité des bactéries (vitesse de nage) est définie par l'électro-conductivité de sa membrane. Si nous ajoutons des azobenzènes et si les azobenzène s'incorpore à la membrane (attachement à la surface ou pénétration dans la membrane) alors nous pouvons essayer de perturber les membranes avec la lumière en excitant les azobenzènes. Cela devrait nous permettre de de développer des nouvelles techniques de la photo-thérapie pour contrôler la motilité des bactéries ou d'autres cellules vivantes / Photodynamic therapy (PDT) is a therapy applicable to many medico-surgical specialties. It consists of the administration of a photosensitizer which concentrates with in a variable time in the lesion to be treated then the illumination of the lesion (by a light of wavelength determined by the absorption spectrum of the photosensitizer) which leads finally to thedestruction of the lesion [1]. The goal of my study project is to study and control the properties of membranes. we are going to use bacteria as artificial membranes. We will use azobenzene molecules in real environments where there are bacteria or otherliving cells. Bacteria have impacts on human health. several bacteria need to move tospecific sites. The most common means of locomotion is the flagellar motor. flagellar bacteria have a rotary motor anchored in their membrane which transmits its rotation to a long filament in the form of a helix lying outside the bacterium via a universal joint called the hook. In addition, flagellar motors play a very important role during bacterial infections. Indeed, bacteria often move in an isotropic media, where the physical properties depend on the direction. the motility of bacteria (swimming speed) is defined by the electro-conductivity of its membrane. If we add azobenzenes and if the azobenzenes become incorporated into the membrane (attachment to the surface or penetration into the membrane) then we can try to perturb the membranes with light by exciting the azobenzenes. This should allow us to develop new phototherapy techniques to control the motility of bacteria or other living cells

The synthesis of galactose clusters that are linked to a steroid moiety by a peptide-like spacer unit is described. The galactose cluster is obtained by Koenigs-Knorr glycosylation of TRIS-Gly-Fmoc (2b) under Helferich conditions. Peptide and ester bonds are formed after activation of carboxylic acids as diphenylthiophene dioxide (TDO) esters. 6a is synthesized in a convergent way by coupling of (Ac4Gal)3-TRIS-Gly (3e) with cholesteryl TDO succinate (5b). Coupling of (Ac4Gal)3-TRIS-Gly hydrogen succinate (3f) with Gly-O-Chol (5d) by means of EEDQ yields 6d. Reaction of (Ac4Gal)3-TRIS-Gly-SUCC-O-TDO (3g) with 25-hydroxycholesterol leads in a linear sequence to the oxysterol derivative 6f. Selective cleavage of the acetyl groups from galactose units yields the known compound 6b and the new derivatives 6e and 6g.

Reproduction de : Thèse de doctorat : Physique : Lyon 1 : 2007. / Titre provenant de l'écran titre. 210 réf. bibliogr.

Seven novel, amphiphilic AApeptides were prepared. Two cationic, lipo-α-AApeptides, NA-75 and NA-77 were found to possess potent antimicrobial activity against Gram-positive bacteria, with almost no hemolytic activity. In addition to NA-75 and 77, four amphiphilic, γ-AApeptides, NA-133, 135, 137, and 139, and one anionic lipo-α-AApeptide, NA-81, were prepared for molecular self-assembly studies, with several interesting nanostructures observed by TEM. Mineralization of calcium carbonate from gaseous CO2 and Ca2+ in the presence of the 7 AApeptide amphiphiles was also observed by optical microscopy. Several AApeptides were found to be able to influence CaCO3 crystal morphology. Another α-AApeptide, NA-63, was synthesized by a novel, alternative method, which has several potential advantages over the previous synthesis methods.

Cationic antimicrobial peptides (CAMPs) are produced by plants, animals and bacteria to protect their host against antagonistic microbes. The antitheses of selective antibiotics, these peptides are drawn by electrostatic and hydrophobic interactions to targets as diverse as the bacterial membrane, nucleic acids and serum proteins. This lack of specificity is their greatest strength, as mutations to single genes rarely lead to bacterial resistance. Resistance may be conferred by large scale alterations in cell envelope composition, which generally reduces bacterial fitness in the absence of peptide. Clinical applications of natural CAMPs are limited, as the peptides are toxic to mammalian cells and rapidly inactivated in vivo by serum albumin and proteases. Faced with these challenges we have prepared a number of CAMP analogues, with the goal of creating lead compounds for further development of antibacterial therapeutics. Much of our work has focused on ultrashort lipopeptides and lipopeptoids, which have properties similar to natural CAMPs and extremely abbreviated sequences. The simple structure of these scaffolds allows rapid creation of CAMP analogues in a brief period of time, allowing us to rapidly explore the structural requirements for CAMP activity. The balance of this work focuses on imparting CAMP-like behaviour to known antibiotics, in order to expand their spectrum of susceptible bacteria and combat the development of drug-resistant bacteria. In particular, the aminoglycosides neomycin and tobramycin have been fused to phenolic disinfectants such as triclosan and biclotymol, in order to improve their diffusion across the bacterial envelope and activity against Gram-negative bacteria.

Cationic antimicrobial peptides (CAMPs) are produced by plants, animals and bacteria to protect their host against antagonistic microbes. The antitheses of selective antibiotics, these peptides are drawn by electrostatic and hydrophobic interactions to targets as diverse as the bacterial membrane, nucleic acids and serum proteins. This lack of specificity is their greatest strength, as mutations to single genes rarely lead to bacterial resistance. Resistance may be conferred by large scale alterations in cell envelope composition, which generally reduces bacterial fitness in the absence of peptide. Clinical applications of natural CAMPs are limited, as the peptides are toxic to mammalian cells and rapidly inactivated in vivo by serum albumin and proteases. Faced with these challenges we have prepared a number of CAMP analogues, with the goal of creating lead compounds for further development of antibacterial therapeutics. Much of our work has focused on ultrashort lipopeptides and lipopeptoids, which have properties similar to natural CAMPs and extremely abbreviated sequences. The simple structure of these scaffolds allows rapid creation of CAMP analogues in a brief period of time, allowing us to rapidly explore the structural requirements for CAMP activity. The balance of this work focuses on imparting CAMP-like behaviour to known antibiotics, in order to expand their spectrum of susceptible bacteria and combat the development of drug-resistant bacteria. In particular, the aminoglycosides neomycin and tobramycin have been fused to phenolic disinfectants such as triclosan and biclotymol, in order to improve their diffusion across the bacterial envelope and activity against Gram-negative bacteria.

Ce travail de thèse décrit la préparation et l'étude des propriétés d'auto-assemblage de nouveaux amphiphiles fonctionnalisés par des sucres. Des glycosides propargyliques du lactose et de la N-acétyl-glucosamine ont été conjugués par chimie click (cycloaddition de Huisgen catalysée par des sels de cuivre) à des dérivés de poly(ethyleneglycol) dont une des extrémités a au préalable été modifiée par une fonction azide et l'autre par un bloc hydrophobe de type polyphénylène ou bien aliphatique. Après une caractérisation par résonance magnétique nucléaire et spectrométrie de masse, les propriétés d'auto-assemblage de ces amphiphiles ont été étudiées par diffusion dynamique de la lumière (DLS), diffraction des rayons-X aux petits angles (SAXS) et microscopie électronique. Il a été montré qu'en phase aqueuse, les systèmes amphiphiles dérivés du PEG 900 s'auto-assemblent pour former de micelles de taille extrêmement régulière dont le diamètre moyen est de l'ordre de 10 nm. La présence et la biodisponibilité des sucres à la surface de ces nanoparticules ont également pu être démontrées par diffusion dynamique de la lumière avec les lectines PNA et WGA. Les interactions spécifiques observées entre les lectines et micelles associées aux propriétés d'encapsulation de ce type de nanoparticules permettent d'imaginer de futures applications pour la délivrance de médicaments ou encore l'imagerie médicale. / This thesis reports the preparation and characterization of new rod-coil amphiphiles functionalized with oligo- and polysaccharides through Huisgen 1,3-dipolar cycloaddition reactions between species functionalized by an azide group on one side and an terminal alkyne on the other catalyzed by copper. The amphiphiles were synthesized and characterized based on different hydrophobic parts conjugated with the polymer poly(ethylene oxide) PEO with a hydrophilic spacer arm and the oligo- and polyssaccharides 2-propargyl-2-acetamido-2-deoxy-β-D-glucopyranose (GlcNAc) and propargyl β-D-galactopyranosyl-(14)-β-D-glucopyranose (Lac). The amphiphiles synthesized were characterized in terms of their chemical structure and composition through nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy, mass spectroscopy (MALDI-TOF-MS and ESI-MS) and high resolution mass spectroscopy (HRMS). After the dissolution in water, the amphiphiles self-associate in highly regular micelles with an average diameter of 2RH ~ 10 nm. Dynamic light scattering (DLS), transmission electron microscopy (TEM) and small angle x-ray scattering (SAXS) were used in order to investigate the structure and dynamics of these saccharide amphiphiles. The presence of carbohydrate epitopes on the surface of the micelles and their bioavailability for the segmentation of lectin were also demonstrated by DLS. Specific interactions of GlcNAc and Lac residues with lectins from wheat germ agglutinin (WGA) and peanut agglutinin (PNA), respectively, reveal the potential applications of such amphiphilic derivatives of carbohydrates as vectorizing systems, both simple and specific to a drug delivery site.

The aim of this dissertation is to investigate self-assembled structures and the phase diagram of amphiphilic molecules of diverse geometric shapes using a number of different computer simulation methods. The semi-realistic coarse-grained model, used extensively for simulation of polymers and surfactant molecules, is adopted in an off-lattice approach to study how the geometric structure of amphiphiles affects the aggregation properties. The results of simulations show that the model system behavior is consistent with theoretical predictions, experiments and lattice simulation models. We demonstrate that by modifying the geometry of the molecules, self-assembled aggregates are altered in a way close to theoretical predictions. In several two and three dimensional off-lattice Brownian Dynamics simulations, the influence of the shape of the amphiphilic molecules on the size and form of the aggregates is studied systematically. Model phospholipid molecules, with two hydrophobic chains connected to one hydrophilic head group, are simulated and the formation of stable bilayers is observed. In addition, (practically very important) mixtures of amphiphiles with diverse structures are studied under different mixing ratios and molecular structures. We find that in several systems, with Poisson distributed chain lengths, the effect on the aggregation distribution is negligible compared to that of the pure amphiphilic system with the mean length of the Poisson distribution. The phase diagrams of different amphiphilic molecular structures are investigated in separate simulations by employing the Gibbs Ensemble Monte Carlo method with an implemented configurational-bias technique. The computer simulations of the above mentioned amphiphilic systems are done in an area where physics, biology and chemistry are closely connected and advances in applications require the use of new theoretical, experimental and simulation methods for a better understanding of their self-assembling properties. Obtained simulation results demonstrate the connection between the structure of amphiphilic molecules and the properties of their thermodynamically stable aggregates and thus build a foundation for many applications of the remarkable phenomena of amphiphilic self-assembly in the area of nanotechnology.

Cette thèse porte sur la détermination des mécanismes de perturbation membranaire de peptides amphiphiles synthétiques de 14 et 21 acides aminés par spectroscopies de RMN à l'état solide et infrarouge. Des études antérieures ont démontré que les peptides 14- et 21- mères possèdent des activités membranaires s'apparentant à celles observées pour les peptides antimicrobiens naturels et leurs analogues. Dans le but de mieux comprendre la nature des interactions impliquées dans leurs modes d'action, et ainsi faire le design et la synthèse de peptides synthétiques possédant une activité antimicrobienne sélective, nous avons étudié les peptides 14- et 21-mères en interaction avec différentes membranes lipidiques modèles. Les membranes modèles utilisées dans cette étude sont les vésicules multilamellaires zwitterioniques et anioniques, les bicouches lipidiques orientées entre des plaques de verre et les bicelles. Dans un premier temps, nous avons étudié l'effet des peptides 14- et 21-mères sur la conformation des têtes polaires et l'ordre orientationnel des chaînes acyle des phospholipides constituant les membranes modèles par spectroscopie de RMN du phosphore-31 et du deutérium. Ces résultats ont révélé que les peptides modèles perturbent davantage la région polaire des bicouches lipidiques, et ont un effet moindre sur les chaînes acyle des lipides. Nous avons également déterminé par spectroscopie de RMN de Pazote-15 que les peptides 14- et 21-mères adoptent une orientation en surface des bicouches orientées entre des plaques de verre. Des mesures de distances hétéronucléaires intermoléculaires ont également confirmé la proximité du peptide 14-mère avec les têtes polaires des lipides DMPC. Dans un dernier temps, nous avons étudié les interactions membranaires et la diffusion rotationnelle du peptide 21-mère en interaction avec des bicelles par RMN P, H et 15N. Les résultats ont révélé que le peptide 21-mère stabilise la structure des bicelles et n'adopte pas une distribution circulaire d'orientation dans le plan des bicelles. Finalement, la dynamique du peptide 21-mère incorporé à des vésicules multilamellaires de DMPC a été étudiée par des expériences en RMN du carbone-13 via l'analyse du nombre et de l'intensité des bandes de rotation, et ces analyses ont révélé que le peptide 21-mère est immobilisé dans son interaction membranaire. / This thesis is related to the determination of the membrane perturbation mechanisms of 14 and 21 amino acid amphipathic synthetic peptides by solid-state NMR and infrared spectroscopies. Previous studies have shown that the 14- and 21-mer peptides exhibit membrane activities similar to those observed for natural antimicrobial peptides and their related analogues. To better understand the type of interactions that are involved in the modes of membrane perturbation of the 14- and 21 -mer peptides, and then to plan the design and synthesis of synthetic peptides with selective antimicrobial activity, we have studied the interaction between the peptides and a variety of model membranes. The types of model membranes used in these studies are zwitterionic and anionic multilamellar vesicles, oriented bilayers stacked between glass plates and bicelles. We first investigated the effects of the 14- and 21-mer peptides on the conformation of polar headgroups and orientational order of lipid acyl chains by phosphorus-31 and deuterium NMR spectroscopy. The results reveal that the 14- and 21-mer model peptides perturb to a greater extent the polar region of phospholipid bilayers, and to a lesser extent the lipid hydrophobic acyl chains. Nitrogen-15 NMR results indicate that the 14- and 21-mer peptides reside at the surface of bilayers stacked between glass plates. Also, intermolecular heteronuclear distance measurements confirm the proximity of the 14-mer peptide to DMPC lipid polar headgroups. We have also studied the membrane interaction and rotational diffusion of the 21- mer peptide in interaction with bicelles by 31P, 2H and 15N NMR. The results reveal that the 21-mer peptide stabilizes the bicelle structure and do not show a circular orientational distribution in the bicelle planar region. Finally, the 21-mer peptide dynamics has been studied by l3C NMR experiments via the analysis of the number and intensity of spinning sidebands, and the results suggest that the 21-mer peptide is immobilized upon binding.

Yes / The possibility of using differential pre‐heating prior to supramolecular gelation to control the balance between hydrogen‐bonding and aromatic stacking interactions in supramolecular gels and obtain consequent systematic regulation of structure and properties is demonstrated. Using a model aromatic peptide amphiphile, Fmoc‐tyrosyl‐leucine (Fmoc‐YL) and a combination of fluorescence, infrared, circular dichroism and NMR spectroscopy, it is shown that the balance of these interactions can be adjusted by temporary exposure to elevated temperatures in the range 313–365 K, followed by supramolecular locking in the gel state by cooling to room temperature. Distinct regimes can be identified regarding the balance between H‐bonding and aromatic stacking interactions, with a transition point at 333 K. Consequently, gels can be obtained with customizable properties, including supramolecular chirality and gel stiffness. The differential supramolecular structures also result in changes in proteolytic stability, highlighting the possibility of obtaining a range of supramolecular architectures from a single molecular structure by simply controlling the pre‐assembly temperature. / FP7 Ideas: European Research Council. Grant Number: 258775