56 research outputs found
Crystal structures and binding dynamics of Odorant-Binding Protein 3 from two aphid species Megoura viciae and Nasonovia ribisnigri
Aphids use chemical cues to locate hosts and find mates. The vetch aphid Megoura viciae feeds exclusively
on the Fabaceae, whereas the currant-lettuce aphid Nasonovia ribisnigri alternates hosts between the
Grossulariaceae and Asteraceae. Both species use alarm pheromones to warn of dangers. For N. ribisnigri this
pheromone is a single component (E)-β-farnesene but M. viciae uses a mixture of (E)-β-farnesene, (-)-α-
pinene, β-pinene, and limonene. Odorant-binding proteins (OBP) are believed to capture and transport such
semiochemicals to their receptors. Here, we report the first aphid OBP crystal structures and examine their
molecular interactions with the alarm pheromone components. Our study reveals some unique structural
features: 1) the lack of internal ligand binding site; 2) a striking groove in the surface of the proteins as a
putative binding site; 3) the N-terminus rather than the C-terminus occupies the site closing off the
conventional OBP pocket. The results from fluorescent binding assays, molecular docking and dynamics
demonstrate that OBP3 from M. viciae can bind to all four alarm pheromone components and the differential
ligand binding between these very similar OBP3s from the two aphid species is determined mainly by the
direct π-π interactions between ligands and the aromatic residues of OBP3s in the binding pocket
Characteristics and properties of nano-LiCoO2 synthesized by pre-organized single source precursors: Li-ion diffusivity, electrochemistry and biological assessment
Background: LiCoO2 is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 degrees C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO2 ( HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li+) ion pathway is expected to be shorter in nanoparticles as compared to micron sized ones. Since batteries typically get recycled, the exposure to nanoparticles during this process needs to be evaluated. Results: Several new single source precursors containing lithium (Li+) and cobalt (Co2+) ions, based on alkoxides and aryloxides have been structurally characterized and were thermally transformed into nanoscale HT-LCO at 450 degrees C within few hours. The size of the nanoparticles depends on the precursor, determining the electrochemical performance. The Li-ion diffusion coefficients of our - LiCoO2 nanoparticles improved at least by a factor of 10 compared to commercial one, while showing good reversibility upon charging and discharging. The hazard of occupational exposure to nanoparticles during battery recycling was investigated with an in vitro multicellular lung model. Conclusions: Our heterobimetallic single source precursors allow to dramatically reduce the production temperature and time for HT-LCO. The obtained nanoparticles of LiCoO2 have faster kinetics for Li+ insertion/extraction compared to microparticles. Overall, nano-sized - LiCoO2 particles indicate a lower cytotoxic and (pro-)inflammogenic potential in vitro compared to their micron-sized counterparts. However, nanoparticles aggregate in air and behave partially like microparticles
Adsorptive removal of methylene blue from colored effluents on fuller's earth
The adsorption behavior of methylene blue (MB) on four fuller's earth (FE) samples of varying compositions was investigated using a spectrophotometric technique to obtain information on the color removal. The distribution coefficient (K-D) increased with an increase in the initial concentration (C-0) of the dye, attained a maximum value, and decreased again at higher initial concentrations. Dye solutions became colorless for a C-0 value corresponding to maximum K-D. A progressively increased flocculation behavior in the clay suspensions was observed and the maximum value of K-D corresponds to optimum flocculation of the clay. The K-D values were found to decrease exponentially after of the solution again became colored while the amount adsorbed increased with an increase in the initial concentration of MB. Only adsorption data obtained for this region could be defined by adsorption isotherm equations. The shifts of the C-0 values corresponding to K-D(max) toward higher concentrations were correlated with the composition of FE samples by using XRF, XRD patterns, and SEM images. The influence of temperature on MB adsorption was also studied and thermodynamic parameters were calculated. (C) 2003 Elsevier Science (USA). All rights reserved
- …