Synthèse d'inhibiteurs potentiels de la D-arabinosyltransférase (vers de nouveaux antibiotiques contre la tuberculose)

La tuberculose est un problème majeur pour la santé mondiale. Son agent pathogène, Mycobacterium tuberculosis, utilise un phospholipide particulier, le béta-D-arabinofuranosyl-1-monophosphodécaprénol (DPA), pour construire sa paroi cellulaire. Le DPA est spécifique des mycobactéries et le sucre qu'il contient n'est pas présent chez les mammifères. Il constitue une cible de choix pour le développement de nouveaux antituberculeux. Cette thèse expose la synthèse d'analogues du DPA pouvant inhiber l'arabinosyltranférase, une des enzymes bâtissant la paroi mycobactérienne. Dans un premier temps, nous avons préparé des analogues dont la liaison phosphate du substrat naturel est remplacé par une liaison phosphonate non sécable par le processus enzymatique naturel. La seconde série d'analogues est constituée de produits dont le cycle furanne a été remplacé par un cycle pyrrolidine. Les iminosucres sont connus pour être de bons inhibiteurs de glycosidases, une classe d'enzymes dont le mécanisme est similaire à l'arabinosyltranférase. Les premiers tests effectués sur l'enzyme seule montrent une inactivité de nos produits qu'il reste à confirmer.Tuberculosis is a major worldwide health problem. Its pathogen agent, Mycobacterium tuberculosis, uses a particular phospholipid, decaprenolphosphoarabinose (DPA), to build its cell wall. DPA is a specific mycobacterial phospholipid and the sugar that it contains is not found in mammalians. It is a good therapeutic target to develop new antituberculosis drugs. This thesis reports the synthesis of DPA analogues, aimed at inhibiting arabinosyltransferase, a key-enzyme involved in the building of mycobacterial cell wall. At first, we have synthesized analogues in which the phosphate linkage has been replaced by a phosphonate linkage. This linkage is not cut by natural enzymatic processes. Products in which the furan cycle of natural substrate cycle has been replaced by a pyrrolidine cycle constitute the second series of analogues. Iminosugars are known to be excellent inhibitors of the related glycosidases. Preliminary tests on crude enzymatic preparation show that our products are inactive but this remains to be confirmed in vivo using Mycobacterium smegmatis as a model of non pathogenic mycobacteria.MULHOUSE-SCD Sciences (682242102) / SudocSudocFranceF

Amphipols and photosynthetic light-harvesting pigment-protein complexes.

International audienc

Synthetic Route to Glycosyl β-1C-(phosphino)-phosphonates as Unprecedented Stable Glycosyl Diphosphate Analogs and Their Preliminary Biological Evaluation

International audienceThe synthesis of glycosyl-β-1C-(phosphino)-phosphonates is a challenge since it has not yet been described. In this paper, we report an innovative synthetic method for their preparation from Glc-, Man-, and GlcNAc-lactone derivatives. The proposed original strategy involves the addition of the corresponding δ-hexonolactones onto the dianion of (methylphosphino) phosphonate as a key step, followed by dehydration and stereoselective addition of dihydrogen on the resulting double bond. Final deprotection provides the new glycosyl diphosphate analogs in 35%, 36%, and 10% yield over 6 steps from the corresponding δ-hexonolactones. The synthetized compounds were evaluated as inhibitors of phosphatase and diphosphatase activities and found to have complex concentration-dependent activatory and inhibitory properties on alkaline phosphatase. The synthetized tools should be useful to study other enzymes such as transferases

Structure-efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds

International audienceNew derivatives of cyclodextrins were prepared in order to determine the relative importance of the structural key elements involved in the degradation of organophosphorus nerve agents. To avoid a competitive inclusion between the organophosphorus substrate and the iodosobenzoate group, responsible for its degradation, the latter group had to be covalently bound to the cyclodextrin scaffold. Although the presence of the α nucleophile iodosobenzoate was a determinant in the hydrolysis process, an imidazole group was added to get a synergistic effect towards the degradation of the agents. The degradation efficiency was found to be dependent on the relative position of the heterocycle towards the reactive group as well as on the nature of the organophosphorus derivative

6-Azido d-galactose transfer to N-acetyl-d-glucosamine derivative using commercially available β-1,4-galactosyltransferase

International audienceA new strategy to tag glycoproteins carrying terminal GlcNAc was developed using commercially available bovine β-1,4-galactosyltransferase (GalT) and UDP-6-azidogalactose. The azide function was then allowed to react via a biotinylated Staudinger–Bertozzi probe demonstrating the usefulness of such a procedure to tag any glycoprotein possessing a N-acetylglucosamine terminal residue from any type of cell lysate

The Disordered Region of the HCV Protein NS5A: Conformational Dynamics, SH3 Binding, and Phosphorylation

Intrinsically disordered proteins (IDPs) perform their physiological role without possessing a well-defined threedimensional structure. Still, residual structure and conformational dynamics of IDPs are crucial for the mechanisms underlying their functions. For example, regions of transient secondary structure are often involved in molecular recognition, with the structure being stabilized (or not) upon binding. Long-range interactions, on the other hand, determine the hydrodynamic radius of the IDP, and thus the distance over which the protein can catch binding partners via so-called fly-casting mechanisms. The modulation of long-range interactions also presents a convenient way of fine-tuning the protein’s interaction network, by making binding sites more or less accessible. Here we studied, mainly by nuclear magnetic resonance spectroscopy, residual secondary structure and long-range interactions in nonstructural protein 5A (NS5A) from hepatitis C virus (HCV), a typical viral IDP with multiple functions during the viral life cycle. NS5A comprises an N-terminal folded domain, followed by a large (~250-residue) disordered C-terminal part. Comparing nuclear magnetic resonance spectra of full-length NS5A with those of a protein construct composed of only the C-terminal residues 191–447 (NS5A-D2D3) allowed us to conclude that there is no significant interaction between the globular and disordered parts of NS5A. NS5A-D2D3, despite its overall high flexibility, shows a large extent of local residual (a-helical and b-turn) structure, as well as a network of electrostatic long-range interactions. Furthermore, we could demonstrate that these long-range interactions become modulated upon binding to the host protein Bin1, as well as after NS5A phosphorylation by CK2. As the charged peptide regions involved in these interactions are well conserved among the different HCV genotypes, these transient long-range interactions may be important for some of the functions of NS5A over the course of the HCV life cycle

Topology optimization of piezoelectric structures : micro-actuators and energy harvesters

International audienceThis paper reviews the primary research effortsconducted within the AS2M department of the FEMTO-STinstitute, focusing on topology optimization of piezoelectricstructures. The paper primarily highlights the principle andthe possibilities offered by topology optimization with aspecific emphasis on the SIMP approach (Solid IsotropicMaterial with Penalization). Then, the design processes ofpiezoelectric micro-actuators and energy harvesters are described.The optimized piezoelectric structures are presentedand the improvements over classical designs are assessed.Finally, the paper discusses the feasibility and the potentialof multi-material topology optimization

Synthesis and biological evaluation of chemical tools for the study of Dolichol Linked Oligosaccharide Diphosphatase (DLODP).

International audienceCitronellyl- and solanesyl-based dolichol linked oligosaccharide (DLO) analogs were synthesized and tested along with undecaprenyl compounds for their ability to inhibit the release of [(3)H]OSP from [(3)H]DLO by mammalian liver DLO diphosphatase activity. Solanesyl (C45) and undecaprenyl (C55) compounds were 50-500 fold more potent than their citronellyl (C10)-based counterparts, indicating that the alkyl chain length is important for activity. The relative potency of the compounds within the citronellyl series was different to that of the solanesyl series with citronellyl diphosphate being 2 and 3 fold more potent than citronellyl-PP-GlcNAc2 and citronellyl-PP-GlcNAc, respectively; whereas solanesyl-PP-GlcNAc and solanesyl-PP-GlcNAc2 were 4 and 8 fold more potent, respectively, than solanesyl diphosphate. Undecaprenyl-PP-GlcNAc and bacterial Lipid II were 8 fold more potent than undecaprenyl diphosphate at inhibiting the DLODP assay. Therefore, at least for the more hydrophobic compounds, diphosphodiesters are more potent inhibitors of the DLODP assay than diphosphomonoesters. These results suggest that DLO rather than dolichyl diphosphate might be a preferred substrate for the DLODP activity