Distinct Behaviour of the Homeodomain Derived Cell Penetrating Peptide Penetratin in Interaction with Different Phospholipids

Penetratin is a protein transduction domain derived from the homeoprotein Antennapedia. Thereby it is currently used as a cell penetrating peptide to introduce diverse molecules into eukaryotic cells, and it could also be involved in the cellular export of transcription factors. Moreover, it has been shown that it is able to act as an antimicrobial agent. The mechanisms involved in all these processes are quite controversial.In this article, we report spectroscopic, calorimetric and biochemical data on the penetratin interaction with three different phospholipids: phosphatidylcholine (PC) and phosphatidylethanolamine (PE) to mimic respectively the outer and the inner leaflets of the eukaryotic plasma membrane and phosphatidylglycerol (PG) to mimic the bacterial membrane. We demonstrate that with PC, penetratin is able to form vesicle aggregates with no major change in membrane fluidity and presents no well defined secondary structure organization. With PE, penetratin aggregates vesicles, increases membrane rigidity and acquires an α-helical structure. With PG membranes, penetratin does not aggregate vesicles but decreases membrane fluidity and acquires a structure with both α-helical and β–sheet contributions.These data from membrane models suggest that the different penetratin actions in eukaryotic cells (membrane translocation during export and import) and on prokaryotes may result from different peptide and lipid structural arrangements. The data suggest that, for eukaryotic cell penetration, penetratin does not acquire classical secondary structure but requires a different conformation compared to that in solution

Graphene oxide/perovskite interfaces for photovoltaics

Graphene-based materials hold a promising prospect for their utilization in perovskite solar cell devices as electron-extraction or hole-transport layers. Here, we investigate the role of oxidized graphene when interfaced with the perovskite MAPbI. Using first-principles calculations based on density functional theory, we study the change in the structural and electronic properties of the heterostructures with the oxidation level. We show that, depending on the concentration of the epoxy functional groups, only reduced graphene oxide would be advantageous for the extraction of photogenerated charge carriers. For oxygen concentration up to 33%, both hole and electron carriers could be extracted, whereas for concentrations between 33 and 66%, electron transfer is favored. For concentrations above 66%, it should not be possible to extract carriers. Moreover, the analysis of the charge density rearrangement at the interface due to the oxidization of graphene shows that the interfacial dipole decreases with the increase in the oxygen content. Finally, we report the modification of the band gap and the work-function in the oxidized graphene for different rearrangements of the epoxy groups on the graphene sheet. This study shows that the reduced graphene oxide with specific oxidation levels could effectively be incorporated as a selective contact in heterojunction devices for applications in perovskite solar cells

Geopolymers from Algerian metakaolin. Influence of secondary minerals

The influence of secondary phases (illite, quartz) on the geopolymerization reaction of metakaolin has been investigated by comparing two metakaolins, one prepared from a pure kaolinite and the other from illite- and quartz-containing Algerian kaolin from the Tamazert region, respectively. Geopolymerization was achieved by mixing the metakaolins with an alkaline sodium silicate solution at room temperature and curing at 50 °C. The products were characterized by X-ray diffraction and 29Si and 27Al MAS-NMR. The results show that the secondary phases, at the concentration used in this work, do not prevent the geopolymerization reactio

Thermal behaviour of kaolin of tamazert (Algeria) deposit

Kaolin from Tamazert deposit in the north Algeria was used in this study. The physical and chemical properties were determined by the performance of several analyses as well as the X-ray fluorescence, X-ray diffraction, thermal behaviour (ATD, TG), dilatometric and granulometric distribution. The study of ceramic behaviour as function of firing temperature has been investigated by shrinkage, adsorption both density and mechanical tests after gradually increasing from room temperature to 1500 °C. The modification of the structure of the raw material samples has been observed after fining and the crystallization of mullite and amorphous silica phase were confirmed by scanning microscopy SEM and evaluated by XRD. The suitability of kaolin for ceramics process was discussed from the linear shrinkage, both density and open porosity. The amorphous phase content is varied from 27-34 % and the tests of flexion have been carried out as depending of temperature, revealed a suitable mechanical properties and the relationship between amorphous phase and sample properties. The adsorption rate was found to be about 35

Graphene oxide/perovskite interfaces for photovoltaics

Graphene-based materials hold a promising prospect for their utilization in perovskite solar cell devices as electron-extraction or hole-transport layers. Here, we investigate the role of oxidized graphene when interfaced with the perovskite MAPbI. Using first-principles calculations based on density functional theory, we study the change in the structural and electronic properties of the heterostructures with the oxidation level. We show that, depending on the concentration of the epoxy functional groups, only reduced graphene oxide would be advantageous for the extraction of photogenerated charge carriers. For oxygen concentration up to 33%, both hole and electron carriers could be extracted, whereas for concentrations between 33 and 66%, electron transfer is favored. For concentrations above 66%, it should not be possible to extract carriers. Moreover, the analysis of the charge density rearrangement at the interface due to the oxidization of graphene shows that the interfacial dipole decreases with the increase in the oxygen content. Finally, we report the modification of the band gap and the work-function in the oxidized graphene for different rearrangements of the epoxy groups on the graphene sheet. This study shows that the reduced graphene oxide with specific oxidation levels could effectively be incorporated as a selective contact in heterojunction devices for applications in perovskite solar cells

Structural characterization of mullite formed from heated kaolin of tamazert deposit (Algeria)

A quantitative analysis of the mullite phase obtained after sintering of the kaolin has been performed by treatment of X ray diagrams. Kaolin is treated in the range of 950-1400 *deg;C. The oxide NiO is added as internal standard after cooling to sintered sample kaolin. Bragg Brentano diffractometer, scanning electron microscopy and differential thermal analysis were used. Analyses of selected directions profile of mullite were carried out by using the adjustment of program, available in the software Highscore of Pan Analytical. The mullite phase that formed from kaolin appears at 1000 °C, observed by XRD and tallies with DTA. The primary mullite crystal showed a plate-like morphology. Two kinds of morphology corresponding to primary (elongated grains) and secondary (equiaxed grains) mullite were observed. A bimodal crystallite size distribution was detected through XRD microstructural analysis from 1300 °C. The apparent sizes obtained of crystallites are determined for mullite with directions-dependent (anisotropy

Adsorption of yellow bemacid CM-3R dye from aqueous solutions onto raw and sodium bentonite

Discharges from the textile industries are heavily loaded with various dyes which requires their treatment. The most common method is to adsorb on solids high surface area, for example, clay material highly available and whose leaves are good natural adsorbents. In present study we used a local bentonite available in its natural form and sodium form for the adsorption of a dye CM-3R yellow bemacid provided by BEZEMA. The evaluation of the effect of various variables is driven by a series of experiments as the contact time, initial concentration of the dye, the initial pH. The different parameters show that the adsorption of the dye is favoured to 240 min, pH 2 and a temperature of 19 ºC. The sodium bentonite yielded good performance results due to the improvement of its adsorption properties. The best correlation of experimental results are obtained with the Langmuir model for sodium bentonite (R % = 0.998) and Freundlich for the raw bentonite (0997

Approche globale et approche ciblée dans la gestion des effluents hospitaliers : application centre de transfusion sanguine, laboratoire sérologie, CHU de Blida

Des études récentes révèlent un danger certain lié aux résidus médicamenteux, produits chimiques, radionucléides, bio films, bactéries résistantes et virus, en aval des stations d’épuration (STEP). Ces résultats confirment l'existence de substances dangereuses dans les effluents hospitalières. Le Centre hospitalo-universitaire Frantz Fanon de Blida s’étale sur superficie de 35 Hectares, d'une capacité globale de 1613 lits, se situe en un point sensible de la Mitidja, Cette plaine s’étend sur une superficie de 1450 km2, d’une épaisseur de 100 à 150 m avec 5 millions habitants. Les potentialités en eau souterraine de cette nappe sont 328 millions m3/an. La production de solutions nuisibles par le C.H.U est estimée à 100 litre par lit et par jour, les rejets peuvent contaminés les eaux de surfaces (Oued Sidi El Kebir, Oued Mazafran) et les eaux souterraines via l’infiltration et la nature perméable des sols. Il est à craindre que les courants souterrains contaminent à long terme une grande partie du sous-sol de la Mitidja. Devant l'urgence et le risque qu'ils représentent, nous avons développé une approche dite ciblée pour une gestion plus efficace des effluents hospitaliers. En effet, dans l’approche globale les effluents hospitaliers sont collectés par un réseau d'assainissement, traités dans une station d'épuration avant d'être rendus dans le mitan naturel. L’approche ciblée évite les rejets dans le réseau d’assainissement de l’hôpital et la STEP, elle neutralise la pollution chimique et biologique à la sortie de chaque enceinte. Par ailleurs, la réalisation d’un laveur désinfecteur d’endoscope adapté à la spécificité des protocoles (exploration digestive, bronchique…) représente une application de l’approche ciblée. En effet, La gestion de la solution désinfectante par asservissement électrotechnique en circuit fermé permet la maitrise de la pollution biologique (ΣBi) et chimique (ΣCi). Il parait que l’évolution des sciences médicales s’accompagne de nouveaux soucis, en plus de la pollution biologique bactérienne et virale en parle aujourd’hui des protéines pathogènes et résistantes au procédés de désinfection usuels. L’approche ciblée reste de mise et insiste sur le développement et l’adaptation de nouvelle technologie dans la procédure de désinfectio