Stress Resistance and Disease Resistance in Seaweeds:The Role of Reactive Oxygen Metabolism

It has become clear that the last 15-20 years that the immediate effect of a wide range of environmental stresses,and of infection,on vascular plants is to increase the information of reactive oxygen species(ROS) and to impose oxidative stress on the cells.Since 1994,sufficient examples similar responses in a broad range of marine macroalgae have been decribed to show that reactive oxygen metabolism also underlies the mechanisms by which seaweeds respond(and become resistant) to stress and infection.Desiccation,freezing,low temperatures,high light,ultraviolet radiation,and heavy metals all tend to result in a gradual and continued buildup of ROS because photosynthesis is inhibited and excess energy results in the formation of singlet oxygen.The response to other stresses (infection or oligosaccharides which signal that infection is occurring,mechanical stress,hyperosmotic shock) is quite different-a more rapid and intence,but short-lived production of ROS ,discribed as an "oxidative burst"-which is attributed to activation of NADPHoxidases in the plasma membrane.Seaweed species that are able to survive such stresses or resist infection have the capacity to remove the ROS through a high cellular content of antioxidant compounds,or a high activity of antioxidant enzymes.

Effects of pH on the Interactions and Conformation of Bovine Serum Albumin: Comparison between Chemical Force Microscopy and Small-Angle Neutron Scattering

The conformation of bovine serum albumin (BSA), as well as its interactions with negatively charged mica surfaces in saline solutions of different pH values, have been studied by small-angle neutron scattering (SANS) and chemical force microscopy (CFM), respectively. A new approach to extract the contribution of elementary interactions from the statistically averaged force-extension curves through self-consistent fitting was proposed and used to understand the effects of pH on the interactions and conformation of BSA in saline solutions. When pH increases, the SANS results reveal that the sizes of BSA molecules increase slightly, while the statistical analysis of the CFM results shows that the averaged pull-off force for the elongation monotonously decreases. The decrease of pull-off force with the increase of pH results from the decrease in the strength of hydrogen bonding and the number of interaction pairs, as well as the slight increase of the strength of van der Waals interaction. When pH approaches the isoelectric point (pI) of BSA, results from both SANS and CFM suggest a loss of long-range interactions in BSA molecules. Our results also suggest that the force-extension curve is mainly contributed by the van der Waals interaction. The combination of SANS and CFM provides new insight to understand the interactions and conformation of BSA molecules

Numerical Simulation of Reactive Extrusion Processes for Activated Anionic Polymerization

In order to deal with the complicated relationships among the variables of the reactive extrusion process for activated anionic polymerization, a three-dimensional equivalent model of closely intermeshing co-rotating twin screw extruders was established. Then the numerical computation expressions of the monomer concentration, the monomer conversion, the average molecular weight and the fluid viscosity were deduced, and the numerical simulation of the reactive extrusion process of Styrene was carried out. At last, our simulated results were compared with Michaeli's simulated results and experimental results. (C) 2007 Elsevier B.V. All rights reserved

Enhanced resonance light scattering based on biocatalytic growth of gold nanoparticles for biosensors design

The biocatalytic growth of gold nanoparticles (Au-NPs) has been employed in the design of new optical biosensors based on the enhanced resonance light scattering (RLS) signals. Both absorption spectroscopy and transmission electron microscopy (TEM) analysis revealed Au-NP seeds could be effectively enlarged upon the reaction with H2O2, an important metabolite that could be generated by many biocatalytic reactions.

Surface-enhanced Raman scattering from surfactant-free 3D gold nanowire networks substrates

A useful method for the fabrication of three-dimensional gold nanowire networks based on the chemical reduction of HAuCl4 with trisodium citrate was presented. The coverage of the 3D gold nanowire networks was tunable by altering precursor concentration. The as-prepared 3D gold nanowire networks could be used as surface-enhanced Raman scattering (SERS) substrates and examined by 4-aminothiophenol (4-ATP) as a probe molecules.

Detection of neurotransmitters by a light scattering technique based on seed-mediated growth of gold nanoparticles

A simple light scattering detection method for neurotransmitters has been developed, based on the growth of gold nanoparticles. Neurotransmitters (dopamine, L-dopa, noradrenaline and adrenaline) can effectively function as active reducing agents for generating gold nanoparticles, which result in enhanced light scattering signals. The strong light scattering of gold nanoparticles then allows the quantitative detection of the neurotransmitters simply by using a common spectrofluorometer.