Multicolor fluorescence imaging of leaves--a useful tool for visualizing systemic viral infections in plants

Abstract Multicolor fluorescence induced by UV light is a sensitive and specific tool that may be used to provide information about the primary and secondary metabolism of plants by monitoring signals of the chlorophyll fluorescence (Chl-F) and blue-green fluorescence (BGF), respectively. We have followed the systemic infection of Nicotiana benthamiana plants with the Pepper mild mottle virus (PMMoV) by means of a multicolor fluorescence-imaging system, to detect differences between two strains of PMMoV during the infection process and to establish a correlation between the virulence and changes induced in the host plant. Changes in both BGF and Chl-F were monitored. BGF increased mainly in the abaxial side of the leaf during pathogenesis and the corresponding images showed a clear vein-associated pattern in leaves of infected plants. HPLC analysis of leaf extracts was carried out to identify compounds emitting BGF, and determined that chlorogenic acid was one of the main contributors. BGF imaging was able to detect viral-induced changes in asymptomatic (AS) leaves before detection of the virus itself. Chl-F images confirmed our previous results of alterations in the photosynthetic apparatus of AS leaves from infected plants that were detected with other imaging techniques. Fluorescence ratios F440/F690 and F440/F740, which increase during pathogenesis, were excellent indicators of biotic stress.     

Efficient and stable titania-based nanocatalytic materials for the reductive amination of furfural

Highly active, selective and stable titania-based catalytic materials have been designed through a simple and environmentally friendly microwave-assisted approach. Further modification of the prepared titania with metal nanoparticles was carried out by a simple chemical reduction method. The synthesized materials displayed excellent catalytic behaviour in the reductive amination of furfural towards furfuryl amine. More importantly, the materials showed remarkable recyclability, retaining high conversion and selectivity values after six reaction cycles.     

[CrIII8MII6]12+ Coordination Cubes (MII=Cu, Co)

[Cr^III₈M^II₆]¹²⁺ (M^II=Cu, Co) coordination cubes were constructed from a simple [Cr^IIIL₃] metalloligand and a “naked” M^II salt. The flexibility in the design proffers the potential to tune the physical properties, as all the constituent parts of the cage can be changed without structural alteration. Computational techniques (known in theoretical nuclear physics as statistical spectroscopy) in tandem with EPR spectroscopy are used to interpret the magnetic behavior.     

Rapid differentiation of isobaric and positional isomers of structurally related glycosides from Phytolacca bogotensis

Through the action of glycosyltransferases, a plant can biosynthetically assemble small different aglycons or 'templates' to various polysaccharides to produce numerous glycoconjugates differing in the type of the attached aglycon, the anomeric configuration of C‐1 of the glycosylating sugar, the type of sugar and the different position of attachments of the sugar unit present in the polysaccharide chain. The position of attachments and the anomeric configuration of the different sugar present in the polysaccharide create the opportunity to generate molecules with either the same or very close molecular weights, which have relative structural similarity – forming isobaric and positional isomers. Although isomeric differentiation was once considered outside of the domain of mass spectrometry, this task can now be resolved using tandem mass spectrometry. In a standardized purified glycoconjugate fraction (SPT01) from Phytolacca bogotensis, we report conventional electrospray ionization mass spectrometry and collision‐induced dissociation (CID) MS/MS parameters which favored the formation of characteristic product ions. This allowed us to suggest the type of sugar linkages present in a specific glycoconjugate. Ten new glycoconjugate are described from this plant and another twelve known saponins were structurally characterized using the automatic MSⁿ acquisition mode. The differentiation of two pairs of positional isomers and four isobaric glycosides and the production of a library of 30 glycosides present in P. bogotensis were accomplished. Copyright © 2009 John Wiley & Sons, Ltd.     

Copper Keplerates: High‐Symmetry Magnetic Molecules

Keplerates are molecules that contain metal polyhedra that describe both Platonic and Archimedean solids; new copper keplerates are reported, with physical studies indicating that even where very high molecular symmetry is found, the low‐temperature physics does not necessarily reflect this symmetry.     

Reduction of different electron-poor N-heteroarylhydrazines in strong basic conditions

The first application of the Wolff-Kishner reduction methodology to electron-poor heteroaromatic compounds is reported. Hydrazino-containing heterocycles with hydrazone-type tautomery have been reduced under basic conditions. This novel chemistry was successfully applied to mono-dehalogenate a number of electron-poor heterocycles in a regioselective manner. According to the experimental results, this reductive process is a base-catalyzed reaction that takes only place in the presence of air, probably through an oxygen-assisted mechanism. As consequence of the specific features of this kind of hydrazone/enehydrazine tautomers, the overall outcome of the process is the synthesis of a Shapiro-type reduction product by simply using a milder version of the Huang-Minlon methodology.     

Trans-ferulic acid valorization into stilbene derivatives via tandem decarboxylation/Heck coupling using Pd/Al-SBA-15 materials

Pd-containing Al-SBA-15 materials were prepared and characterized in view of their utilization in the two-step valorization of trans-ferulic acid into stilbenes via tandem decarboxylation/Mizoroki-Heck coupling. Materials were found to be highly active and selective in the proposed chemistries, with quantitative conversion to target products under mild reaction conditions (typically 100 °C, 3–6 h reaction). Relevant insights on catalyst deactivation via sintering (Pd nanoparticles agglomeration) were also observed for the synthesized materials.