Predicting the Structure and Dynamics of Membrane Protein GerAB from Bacillus subtilis

Bacillus subtilis forms dormant spores upon nutrient depletion. Germinant receptors (GRs) in spore’s inner membrane respond to ligands such as L-alanine, and trigger spore germination. In B. subtilis spores, GerA is the major GR, and has three subunits, GerAA, GerAB, and GerAC. L-Alanine activation of GerA requires all three subunits, but which binds L-alanine is unknown. To date, how GRs trigger germination is unknown, in particular due to lack of detailed structural information about B subunits. Using homology modelling with molecular dynamics (MD) simulations, we present structural predictions for the integral membrane protein GerAB. These predictions indicate that GerAB is an α-helical transmembrane protein containing a water channel. The MD simulations with free L-alanine show that alanine binds transiently to specific sites on GerAB. These results provide a starting point for unraveling the mechanism of L-alanine mediated signaling by GerAB, which may facilitate early events in spore germination.     

Influence of the structure of the onium iodide salts on the properties of modified montmorillonite

Dialkyl imidazoline, alkyl pyridine and alkyl quinoline containing salts have been synthesized and used as new surfactants for cationic exchange of layered silicates, such as montmorillonite (MMT) in order to evaluate their role in the formation of intercalated MMT clays. The new salts have been characterized by FTIR, ¹H, ¹³C‐NMR spectra. These compounds have been intercalated into the layers of MMT via a solution dispersion technique and the extent of the interlayer space expansion was confirmed by using wide angle X‐ray diffraction and FTIR spectra. Thermogravimetry analysis shows that these salts can be used in place of ammonium salts to produce organophilic clays with higher thermal stability than commercial alkyl ammonium‐treated MMT. Moreover, the results also show that the imidazolium‐modified clays have a greater thermal stability compared to the quinolinium and the pyridinium‐modified clay. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphology and thermo-mechanical properties of new hybrid coatings based on polyester/melamine resin and pyrogenic silica

Polyester/melamine (PM)-based formulations used in coil-coating applications were modified with pyrogenic silicas of different types. The influence of the chemical modification of the silica surface on various properties was investigated. The viscosity of filled PM formulations was measured. Transmission electron microscopy and dynamic mechanical measurements were used to characterize nanocomposite films. Roughness and gloss measurements were done on nanocomposite coatings. The results show that the viscosity and morphology observed are directly linked to the balance and nature of the interactions developed between the silica surface and the organic medium. Both hydrophilic and hydrophobic silica lead to too high viscosity of the filled formulation, to different silica dispersion and, as a consequence, to low gloss coatings. However with an adequate organo-modification of the silica, formulations compatible with the process and having a high gloss can be obtained. Additionally, the surface modification of silica has no obvious influence on the dynamic mechanical properties.     

Endoglin is an accessory protein that interacts with the signaling receptor complex of multiple members of the transforming growth factor-beta superfamily

Endoglin (CD105) is a transmembrane glycoprotein that binds transforming growth factor (TGF)-beta1 and -beta3, and coprecipitates with the Ser/Thr kinase signaling receptor complex by affinity labeling of endothelial and leukemic cells. The present study shows that in addition to TGF-beta1 and -beta3, endoglin interacts with activin-A, bone morphogenetic protein (BMP)-7, and BMP-2 but requires coexpression of the respective ligand binding kinase receptor for this association. Endoglin cannot bind ligands on its own and does not alter binding to the kinase receptors. It binds TGF-beta1 and -beta3 by associating with the TGF-beta type II receptor and interacts with activin-A and BMP-7 via activin type II receptors, ActRII and ActRIIB, regardless of which type I receptor partner is coexpressed. However, endoglin binds BMP-2 by interacting with the ligand binding type I receptors, ALK3 and ALK6. The formation of heteromeric signaling complexes was not altered by the presence of endoglin, although it was coprecipitated with these complexes. Endoglin did not interact with BMP-7 through complexes containing the BMP type II receptor, demonstrating specificity of its action. Our data suggest that endoglin is an accessory protein of multiple kinase receptor complexes of the TGF-beta superfamily.     

Kinetics modeling of a modified epoxy–amine formulation cured by thermal and microwave energy

The reaction kinetics of a rubber-modified epoxy formulation cured by microwave or thermal energy were investigated. Two phenomenological models were developed to predict the time and temperature dependence of the conversion for the neat and the modified systems. Good agreement was observed between the kinetic models and experimental results generated by chromatographic and calorimetric techniques. The same kinetic behavior was observed whatever the curing process (conventional or microwave heating). © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 543–552, 1998     

Catalytic wet peroxide oxidation of phenol over Fe-exchanged pillared beidellite

This study presents an evaluation of the catalytic performances of a Fe-exchanged Al-pillared synthetic beidellite for the wet hydrogen peroxide oxidation of phenolic aqueous wastes. The catalyst was prepared by a cation doping technique, its properties being determined by DRX, BET and chemical analysis techniques. All the tests were performed on a laboratory scale set-up.Important factors affecting catalyst activity and phenol removal efficiencies were studied, i.e. the effect of pH, temperature, catalyst concentration and the stability of the catalyst. The experimental results indicate that the use of this catalyst allows a total elimination of phenol and a significant removal of chemical oxygen demand, without significant leaching of Fe ions. Thus, considering the lowest Fe concentrations in solution after oxidation, at pH=5, 50 degrees C, and 180 min. COD removal efficiency of 87.9% was obtained. It was also observed that by using this catalyst, it is possible to extend the range of pH values for which Fenton-type oxidations can occur.     

The impact of selective amygdala, orbital frontal cortex, or hippocampal formation lesions on established social relationships in rhesus monkeys (Macaca mulatta).

Social dominance, personality ratings, and frequency, duration, and timing of social behaviors were measured pre- and postsurgically in 6 groups of rhesus monkeys (Macaca mulatta), each consisting of 1 sham-operated control and 1 monkey each with a selective amygdala, hippocampal, or orbital frontal cortex lesion. Unlike previous reports, none of the operated groups showed changes in social dominance postsurgery, although changes in other measures varied by lesion site. Although sham-operated monkeys displayed heightened avoidant, anxious, and aggressive behaviors, those with hippocampal lesions also showed increased exploration and excitability, along with reduced responses to affiliative signals. Amygdala lesions yielded several personality changes that precluded positive social interactions (increased exploration and excitability, decreased affiliation and popularity) and altered responses to threatening social signals. By contrast, monkeys with orbital frontal lesions were involved in more aggressive interactions and responded differently to both affiliative and threatening signals. Although several findings differ from earlier nonhuman primate studies, they are largely in agreement with human data and emphasize the context-specific nature of social behavior studies. Interpretation of results in relation to cognitive processes mediated by each structure is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Preparation of new microporous titanium pillared kenyaite materials active for the photodegradation of methyl orange

In recent years, layered silicates have extensively been used to design new nanomaterials through functionalization. In this work, the lamellar sodium silicates magadiite and kenyaite have been hydrothermally synthesized in presence of ethanol as organic co-solvent. Materials of high purity and high crystallinity were obtained after only 24 h of crystallization at a temperature of 180 °C for kenyaite and a temperature of 150 °C for magadiite. It appears that the presence of ethanol in the synthesis medium tends not only to increase the crystallization rate, but also to stabilize the formation of magadiite.The as-synthesized Na-kenyaite was used as precursor for the preparation of titanium pillared clay materials. The resulting microporous titanium oxide pillared kenyaite materials exhibit large specific surface areas up to 180 m² g^?1 with a Ti contents up to 24 wt% and are active for the photocatalytic degradation under UV light irradiation of the organic dye methyl orange in water.