Effects of counter-ions and volume on the simulated dynamics of solvated proteins. Application to the activation domain of procarboxypeptidase B

Molecular dynamics (MD) simulations of the globular activation domain of porcine procarboxypeptidase B (ADBp) and its isolated alpha-helix 1 were performed in order to understand the effects of adding salts and using periodic boundary conditions (this being reflected in the box size) along the simulations. alpha-Helix 1 was chosen because it is the most charged element of the secondary structure within ADBp. Different types of MD simulations with the GROMOS package were performed, studying either the whole activation domain or the isolated alpha-helix 1 with different water box sizes and counter-ionic shells. The analyses of the trajectories show that simulations of solvated proteins are highly sensitive to the presence of counter-ions and less sensitive to the volume of the water box. The differences in protein potential energies, r.m.s. deviations and radius of gyration between the simulations with and without counter-ions demonstrate that during such studies secondary structures of proteins are more stable when their charges are carefully neutralized. This stresses the need for such a procedure when analysing significantly charged proteins. The results also showed that the enlargement of the water box helps in the stabilization of the system.     

Dilatometric behavior and microstructure of sintered Fe–NbC and Fe–TaC composites

Fe-reinforced composites were manufactured by the addition of 10–20 wt.% NbC or TaC particles aiming at improved mechanical and wear behavior. Two varieties of Fe powders from Hoeganaes Corp. were used, Ancorsteel 1000B and 45P. Composites produced using the former variety included a small amount of Fe₃P to induce liquid-phase sintering whereas 45P powder was pre-alloyed with P by the manufacturer. The hardness of the matrix was adjusted adding carbon to the composite mixture. The powders were milled for different times and annealed prior to pressing. A dilatometric study was carried out under hydrogen to establish optimum sintering profiles. Relative densities up to 97% TD were achieved. Both microstructure and density of the sintered pellets were evaluated in order to establish correlations involving composition, processing parameters and microstructure of the composite.     

Learning to Match the Schemas of Data Sources: A Multistrategy Approach

The problem of integrating data from multiple data sources—either on the Internet or within enterprises—has received much attention in the database and AI communities. The focus has been on building data integration systems that provide a uniform query interface to the sources. A key bottleneck in building such systems has been the laborious manual construction of semantic mappings between the query interface and the source schemas. Examples of mappings are element location maps to address and price maps to listed-price. We propose a multistrategy learning approach to automatically find such mappings. The approach applies multiple learner modules, where each module exploits a different type of information either in the schemas of the sources or in their data, then combines the predictions of the modules using a meta-learner. Learner modules employ a variety of techniques, ranging from Naive Bayes and nearest-neighbor classification to entity recognition and information retrieval. We describe the LSD system, which employs this approach to find semantic mappings. To further improve matching accuracy, LSD exploits domain integrity constraints, user feedback, and nested structures in XML data. We test LSD experimentally on several real-world domains. The experiments validate the utility of multistrategy learning for data integration and show that LSD proposes semantic mappings with a high degree of accuracy.     

Microglial Cell Activation Increases Saturated and Decreases Monounsaturated Fatty Acid Content,but Both Lipid Species are Proinflammatory

Neuroinflammation is a component of age-related neurodegenerative diseases and cognitive decline. Saturated (SFA) and monounsaturated (MUFA) fatty acids are bioactive molecules that may play different extrinsic and intrinsic roles in neuroinflammation, serving as exogenous ligands for cellular receptors, or endogenous components of cell structural, energetic and signaling pathways. We determined the fatty acyl profile of BV2 microglial cells before and after acute activation with lipopolysaccharide (LPS). We also investigated the effect of SFA and MUFA pretreatment on the production of an invasive, neurotoxic phenotype in BV2 cells. Acute activation of BV2 microglia resulted in an increase in the relative content of SFA (12:0, 16:0, 18:0, 20:0, 22:0, and 24:0 increased significantly), and a relative decrease in the content of MUFA (16:1n7, 18:1n7, 18:1n9, 20:1n9, 24:1n9 decreased significantly). In agreement, the major stearoyl-CoA desaturase (SCD) isoform in BV2 cells, SCD2, was significantly down-regulated by LPS. We next treated cells with SFA (16:0 or 18:0) or MUFA (16:1n7 or 18:1n9), and found that levels of secreted IL6 were increased, as was secreted MMP9-mediated proteolytic activity. To test the functional significance, we treated SH-SY5Y neuronal cells with conditioned medium from BV2 cells pretreated with fatty acids, and found a small but significant induction of cell death. Our findings suggest differential intrinsic roles for SFA and MUFA in activated microglial cells, but similar extrinsic roles for these fatty acid species in inducing activation. Expansion of SFA is important during microglial cell activation, but either supplemental SFA or MUFA may contribute to chronic low-grade neuroinflammation.     

Texture and Porosity Effects on the Thermal Radiative Behavior of Alumina Ceramics

Thermal and optical properties of ceramics are dependent on radiation scattering and cannot be determined by a knowledge of their chemical composition alone, as for single crystals. In this paper, extrinsic effects, such as roughness, porosity, and texture, on the spectral emissivity of alumina ceramics are investigated. Roughness effects have an influence mainly in the opaque zone; an important porosity dependence and the presence of a critical porosity threshold were observed in the semitransparent zone. Furthermore, it was shown that two ceramics with similar total porosities, but with different textures, possess radically different emissivities, showing that grain size, pore size, and spatial repartition of the grains are also crucial for an understanding of the thermal properties of the ceramics. This study was performed at CEMTHI laboratory.