Association of cone thermogenesis and volatiles with pollinator specificity in Macrozamia cycads

Cone traits (volatile components and thermogenesis) of three cycad species in the genus Macrozamia were examined for differences related to their specific insect pollinators, the weevil, Tranes spp., or the thrips, Cycadothrips chadwicki. Linalool (>80% of emissions) dominated cone volatile components of M. machinii (Tranes-pollinated) and beta-myrcene was a minor component (

Molecular dynamics simulation of the structural and dynamic properties of dioctadecyldimethyl ammoniums in organoclays

The structural and dynamic properties of dioctadecyldimethylammoniums (DODDMA) intercalated into 2:1 layered clays are investigated using isothermal-isobaric (NPT) molecular dynamics (MD) simulation. The simulated results are in reasonably good agreement with the available experimental measurements, such as X-ray diffraction (XRD), atom force microscopy (AFM), Fourier transform infrared (FTIR), and nuclear magnetic resonance (NMR) spectroscopies. The nitrogen atoms are found to be located mainly within two layers close to the clay surface whereas methylene groups form a pseudoquadrilayer structure. The results of tilt angle and order parameter show that interior two-bond segments of alkyl chains prefer an arrangement parallel to the clay surface, whereas the segments toward end groups adopt a random orientation. In addition, the alkyl chains within the layer structure lie almost parallel to the clay surface whereas those out of the layer structure are essentially perpendicular to the surface. The trans conformations are predominant in all cases although extensive gauche conformations are observed, which is in agreement with previous simulations on n-butane. Moreover, an odd-even effect in conformation distributions is observed mainly along the chains close to the head and tail groups. The diffusion constants of both nitrogen atoms and methylene groups in these nanoconfined alkyl chains increase with the temperature and methelene position toward the tail groups.

Comparisons of the structural and catalytic properties of Ti-HMS synthesized using the hydrothermal and molecular designed dispersion methods

Titanium containing wormhole-like mesoporous silicas, denoted Ti-HMS, synthesized both via the hydrothermal synthesis route and the post synthesis grafting technique, known as molecular designed dispersion, have been successfully applied in the gas phase oxidation of Toluene to CO and CO2. Selectivity towards CO2 for all catalysts, at temperatures between 400-600degreesC, was above 80%. Benzene and benzaldehyde were observed at temperatures above 450degreesC, but in very low concentrations. The conversion of toluene was shown to increase significantly when the V-TEX/N-MESO ratios were increased from 0.07 to 0.84. No significant difference in catalytic activity was observed for catalysts prepared via the different synthesis techniques. The catalytic activity also depends on the concentration of tetrahedrally coordinated titanium atoms and not on the total concentration of titanium in the catalyst.

Structural and functional characterization of the conserved salt bridge in mammalian Paneth cell alpha-defensins - Solution structures of mouse cryptdin-4 AND (E15D)-cryptdin-4

Defensins are mediators of mammalian innate immunity, and knowledge of their structure-function relationships is essential for understanding their mechanisms of action. We report here the NMR solution structures of the mouse Paneth cell α-defensin cryptdin-4 (Crp4) and a mutant (E15D)-Crp4 peptide, in which a conserved Glu15 residue was replaced by Asp. Structural analysis of the two peptides confirms the involvement of this Glu in a conserved salt bridge that is removed in the mutant because of the shortened side chain. Despite disruption of this structural feature, the peptide variant retains a well defined native fold because of a rearrangement of side chains, which result in compensating favorable interactions. Furthermore, salt bridge-deficient Crp4 mutants were tested for bactericidal effects and resistance to proteolytic degradation, and all of the variants had similar bactericidal activities and stability to proteolysis. These findings support the conclusion that the function of the conserved salt bridge in Crp4 is not linked to bactericidal activity or proteolytic stability of the mature peptide.