Interaction of an acid protease with positively charged phosphatidylcholine bilayers

Positively charged bilayers composed of phosphatidylcholine (PC) and stearylamine (SA) in a 4:1 ratio reduce the effectiveness of a protease from Mucor miehei to produce milk clotting. This is related to the adsorption of the protein, which at pH 7 is negatively charged, by electrostatic forces. However, an increase in SA, which increases the membrane packing parallel to the increase in the surface charge density, counteracts the protein membrane association. This is in agreement with the fact that the protease can also adsorb on pure phosphadylcholine bilayers in the fluid state but not in the gel state. In addition, the presence of phosphatidylethanolamine also inhibits protease adsorption. It is concluded that the protein affects the membrane interface of fluid PC membranes because the electrostatic charges pull the protein to the bilayer interface causing changes in hydration and area per molecule. The adsorption is only at the level of the polar head groups since no effects were observed in the hydrocarbon core region.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Structural properties and Raman spectroscopy of lipid Langmuir monolayers at the air-water interface

Spectra of octadecylamine (ODA) Langmuir monolayers and egg phosphatidylcholine (PC)/ODA-mixed monolayers at the air-water interface have been acquired. The organization of the monolayers has been characterized by surface pressure-area isotherms. Application of polarized optical microscopy provides further insight in the domain structures and interactions of the film components. Surface-enhanced Raman scattering (SERS) data indicate that enhancement in Raman spectra can be obtained by strong interaction between headgroups of the surfactants and silver particles in subphase. By mixing ODA with phospholipid molecules and spreading the mixture at the air-water interface, we acquired vibrational information of phospholipid molecules with surfactant-aided SERS effect.Comment: 8 pages, 9 figure

Interaction of an acid protease with positively charged phosphatidylcholine bilayers

Positively charged bilayers composed of phosphatidylcholine (PC) and stearylamine (SA) in a 4:1 ratio reduce the effectiveness of a protease from Mucor miehei to produce milk clotting. This is related to the adsorption of the protein, which at pH 7 is negatively charged, by electrostatic forces. However, an increase in SA, which increases the membrane packing parallel to the increase in the surface charge density, counteracts the protein membrane association. This is in agreement with the fact that the protease can also adsorb on pure phosphadylcholine bilayers in the fluid state but not in the gel state. In addition, the presence of phosphatidylethanolamine also inhibits protease adsorption. It is concluded that the protein affects the membrane interface of fluid PC membranes because the electrostatic charges pull the protein to the bilayer interface causing changes in hydration and area per molecule. The adsorption is only at the level of the polar head groups since no effects were observed in the hydrocarbon core region.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Adhesive glycostrategies from opportunistic filamentous fungi

International audienc

High Resolution Genotyping of Clinical Aspergillus flavus Isolates from India Using Microsatellites

Contains fulltext : 124312.pdf (publisher's version ) (Open Access)BACKGROUND: Worldwide, Aspergillus flavus is the second leading cause of allergic, invasive and colonizing fungal diseases in humans. However, it is the most common species causing fungal rhinosinusitis and eye infections in tropical countries. Despite the growing challenges due to A. flavus, the molecular epidemiology of this fungus has not been well studied. We evaluated the use of microsatellites for high resolution genotyping of A. flavus from India and a possible connection between clinical presentation and genotype of the involved isolate. METHODOLOGY/PRINCIPAL FINDINGS: A panel of nine microsatellite markers were selected from the genome of A. flavus NRRL 3357. These markers were used to type 162 clinical isolates of A. flavus. All nine markers proved to be polymorphic displaying up to 33 alleles per marker. Thirteen isolates proved to be a mixture of different genotypes. Among the 149 pure isolates, 124 different genotypes could be recognized. The discriminatory power (D) for the individual markers ranged from 0.657 to 0.954. The D value of the panel of nine markers combined was 0.997. The multiplex multicolor approach was instrumental in rapid typing of a large number of isolates. There was no correlation between genotype and the clinical presentation of the infection. CONCLUSIONS/SIGNIFICANCE: There is a large genotypic diversity in clinical A. flavus isolates from India. The presence of more than one genotype in clinical samples illustrates the possibility that persons may be colonized by multiple genotypes and that any isolate from a clinical specimen is not necessarily the one actually causing infection. Microsatellites are excellent typing targets for discriminating between A. flavus isolates from various origins

Metabolic Variation during Development in Culture of Leishmania donovani Promastigotes

The genome sequencing of several Leishmania species has provided immense amounts of data and allowed the prediction of the metabolic pathways potentially operating. Subsequent genetic and proteomic studies have identified stage-specific proteins and putative virulence factors but many aspects of the metabolic adaptations of Leishmania remain to be elucidated. In this study, we have used an untargeted metabolomics approach to analyze changes in the metabolite profile as promastigotes of L. donovani develop during in vitro cultures from logarithmic to stationary phase. The results show that the metabolomes of promastigotes on days 3–6 of culture differ significantly from each other, consistent with there being distinct developmental changes. Most notable were the structural changes in glycerophospholipids and increase in the abundance of sphingolipids and glycerolipids as cells progress from logarithmic to stationary phase

Déploiement d'Applications à Services sur des Environnements d'Exécution à Services : Une Approche Dirigée par les Modèles.

Done !Our goal is to provide Internet services on top of "n-tier" architectures. In our context, these architectures are made of five tiers: devices, gateways, mediation, Internet servers and presentation. Apprehending the gateways tier needs the introduction of services applications to answer the requests of the mediation tier and to collect and transform data from the "devices" tier, these data are then used by the "mediation" tier, next they are manipulated by the "Internet server" tier which is in charge of the displaying to the end users. The introduction of such services applications intended to run in services execution environments raises issues related to: - the development of business-specific services applications [ML07], - their deployment in services execution environments (this is the focus of this thesis) [CL07a] - the dynamic management of interactions between services applications and the devices (un)- plugged to the gateways (these devices are exposed as services in the environments) [EBL+08]. Software lifecycle is made of several phases. The main ones are analysis, conception, implementation, test and deployment. The latter is a complex one; it is made of activities and subactivities like installation, activation, deactivation, static and dynamic updates, evolution, dynamism and deinstallation. The introduction and use of the service approach still raises the deployment phase complexity, in particular when the goal is the deployment of services applications on services execution environments. Stakes, here, are: - to execute deployment activities targeting services applications while respecting each application's architecture (i.e. each application's model), - to control the deployment state of the services (implementations) realizing these applications, - to execute deployment activities on services belonging to these applications while acting only the targeted service and avoiding to impact the whole applications. We called this last stake: "closely deployment" or "deployment in the small". It imposes that development units (i.e. constraints service-oriented components) used for developing applications and deployment units (i.e. services implementations) used for realizing applications have the same (fine) grain. This thesis proposes a software prototype, called DMSA (for Deployment Manager for Services Applications), automating the deployment of services applications on services execution environments while following a model-driven approach. Using a model-driven approach is an answer for the constant rise in abstraction of the deployment phase and of its entry point. The full decoupling between model level and "reality" level has been chosen in order to reuse services implementations between services models. This document clarifies our approach, the services applications meta-model, the services applications deployment definition, the DMSA's software architecture and our propositions. These latter target deployment of several applications models on several services execution environments, "transactional" deployment, our embedded context apprehension and execution of deployment activities ordered lists on services execution environments.Notre objectif est la fourniture de services Internet basés sur des architectures "n-tiers". Dans notre contexte, ces architectures sont composées de cinq tiers : "équipements", "passerelles", "médiation", "serveur Internet" et "clients finaux". L'appréhension du tiers "passerelle" nécessite l'introduction d'applications à services qui sont destinées à répondre à des requêtes du tiers "médiation" et à collecter et transformer des données provenant du tiers "équipements" qui seront ensuite utilisées par le tiers "médiation" puis manipulées par le tiers "serveur Internet" qui est chargé de leur présentation aux clients finaux. L'introduction de telles applications à services destinées à fonctionner dans des environnements d'exécution à services nécessite la résolution de problématiques propres : - au développement d'applications à services métiers [ML07], - à leur déploiement dans des environnements d'exécution à services (ce qui est l'objectif de cette thèse) [CL07a] - à la gestion dynamique des interactions entre les applications à services et les équipements (dé)- branchés à la passerelle (qui sont exposées comme des services) [EBL+08]. Le cycle de vie logiciel est composé de plusieurs phases. Les principales sont l'analyse, la conception, l'implémentation, le test et le déploiement. Cette dernière est une phase complexe qui est composée d'activités et de sous-activités comme l'installation, l'activation, la désactivation, les mises à jour statique et dynamique, l'évolution, le dynamisme et la désinstallation. L'introduction et l'utilisation de l'approche à service augmente encore la complexité de la phase de déploiement, en particulier lorsqu'il s'agit de déployer des applications à services sur des environnements d'exécution à services. Les enjeux sont, ici : - d'exécuter des activités de déploiement sur les applications tout en respectant l'architecture de chaque application (c'est-à-dire le modèle de chaque application), - de maîtriser l'état de déploiement des (implémentations de) services réalisant ces applications, - d'exécuter des activités de déploiement sur des services appartenant à ces applications en ne touchant que le service ciblé et donc sans impacter entièrement les applications dans leur ensemble. Nous appelons ce dernier enjeu : "déploiement au plus près". Il impose que les unités de développement (c'est-à-dire les composants orientés service contraints) utilisées pour développer les applications et les unités de déploiement (c'est-à-dire les implémentations de services) utilisées pour réaliser les applications aient le même grain. Cette thèse propose un prototype, nommé DMSA (pour Deployment Manager for Services Applications), automatisant le déploiement d'applications à services sur des environnements à services en suivant une approche dirigée par les modèles. L'utilisation de l'approche dirigée par les modèles est une réponse à la constante montée en abstraction du déploiement et de son point d'entrée. Le découplage total entre les niveaux modèles et "réalité" a été choisi afin de permettre la réutilisation des implémentations de services entre modèles de services. Cette thèse explicite notre approche, le méta-modèle pour les applications à services, la définition du déploiement pour les applications à services, l'architecture du DMSA et nos propositions. Ces dernières ciblent le déploiement d'un, puis de plusieurs modèles d'application à services sur un environnement d'exécution à services, le déploiement "transactionnel", l'appréhension de notre contexte embarqué/réactif et l'exécution de listes ordonnées d'activités de déploiement sur des environnements d'exécutions à services