The Heterotrimeric G-protein Complex Modulates Light Sensitivity in Arabidopsis thaliana Seed Germination

Release of dormancy and induction of seed germination are complex traits finely regulated by hormonal signals and environmental cues such as temperature and light. The Red (R):Far-Red (FR) phytochrome photoreceptors mediate light regulation of seed germination. We investigated the possible involvement of heterotrimeric G-protein complex in the phytochrome signaling pathways of Arabidopsis thaliana seed germination. Germination rates of null mutants of the alpha (Gα) and beta (Gβ) subunits of the G-protein (At gpa1-4 and agb1-2 , respectively) and the double mutant ( agb1-2/gpa1-4 ) are lower than the wildtype (WT) under continuous or pulsed light. The Gα and Gβ subunits play a role in seed germination under hourly pulses of R lower than 0.1 μmol m⁻² s⁻¹ whereas the Gβ subunit plays a role in higher R fluences. The germination of double mutants of G-protein subunits with phyA-211 and phyB-9 suggests that AtGPA1 seems to act as a positive regulator of phyA and probably phyB signaling pathways, while the role of AGB1 is ambiguous. The imbibition of seeds at 4°C and 35°C alters the R and FR light responsiveness of WT and G-protein mutants to a similar magnitude. Thus, Gα and Gβ subunits of the heterotrimeric G-protein complex modulate light induction of seed germination by phytochromes and are dispensable for the control of dormancy by low and high temperatures prior to irradiation. We discuss the possible indirect role of the G-protein complex on the phytochrome-regulated germination through hormonal signaling pathways.     

Xanthopterin in the Oriental Hornet (Vespa orientalis): Light Absorbance Is Increased with Maturation of Yellow Pigment Granules

The Oriental hornet bears both brown and yellow colors on its cuticle. The brown component is contributed by the pigment melanin, which is dispersed in the brown cuticle and provides protection against insolation, while the yellow‐colored part contains within pockets in the cuticle granules possessing a yellow pigment. These yellow granules (YG) are formed about 2 days prior to eclosion of the imago, and their production continues for about 3 days posteclosion. Xanthopterin is the main component of the granule and lends it its yellow color. Xanthopterin produces a characteristic excitation/emission maximum at 386/456 nm. Characterization by use of mass spectrometry showed the compound to have a molecular ion of 179, as expected from xanthopterin. Spectroscopic examination of the absorption of an entire stripe of yellow cuticle in the course of its metamorphosis revealed that the absorption steadily increases throughout the process to a maximal level of absorption about 3 days posteclosion. In the absence of the YG, the cuticle is permeable to the passage of all wavelengths within the visible range and to the UV range (290–750 nm) in all age groups of hornets. The newly ecloded hornets depart the nest to engage in activities requiring exposure to insolation only as the process of granule formation terminates, namely, when the layer of YG in the cuticle suffices to absorb all the harmful UV radiation.     

Transport Phenomena and Electrode Reactions Generated by an Electric Field in Colloidal Silica

The kinetics of transport phenomena generated by an electric field and leading to the formation of density gradients in suspensions of charged colloidal silica were studied by using various electrodes. The rate of approach to a steady-state density gradient was found to be much higher when using metallic electrodes (Cu, Fe, and Pt) in comparison with graphite (C) electrodes. Nevertheless, the initial rate with C electrodes was substantially increased by the addition of hydroquinone-quinone because the redox reactions, necessary for electrode-electrolyte current transfer, occur at lower potential compared with the electrolysis of water. On the other hand, the products of oxidation of hydroquinone which accumulate in the system bring about an important decrease of the zeta potential of silica particles and progressive deceleration of their electrophoretic mobility. A detailed study was carried out, by using thin-layer isoperichoric focusing, UV-vis spectrophotometry, and voltamperometry, to explain the observed phenomena which can interfere in electric polarization or focusing field-flow fractionation. Copyright 2000 Academic Press.     

Electric Field‐Assisted Photochemical Water Splitting Should Operate with 287 nm Light

The major photoreaction of water is the homolytic splitting of one O–H bond starting from the 1¹B₁ excited state (λ_max = 167 nm). This reaction produces H? and ?OH radicals. The combination of two H? atoms leads to the potential energy carrier dihydrogen. However, the energy required to obtain the photoreactive 1¹B₁ electronic state is about 7.4 eV, which cannot be effectively provided by solar radiation. The sun light spectrum on earth comprises the visible and ultraviolet region, but shows vanishing intensity near 7 eV (177.1 nm). This work provides theoretical evidence that the photoreactive 1¹B₁ state of water can be shifted into the ultraviolet (UV‐B) light region (≈287 nm) by including explicitly an electric field in the calculations of the water absorption spectrum. To accomplish such bathochromic shift, a large field strength of 3.08 VÅ^?1 is required. The field‐dependent excitation energies were calculated by applying the symmetry‐adapted cluster configuration interaction (SAC‐CI) procedure. Based on this theoretical analysis, we propose that photochemical water splitting can be accomplished by means of 287 nm light provided the water molecule is favorably oriented by an external electric field and is subsequently activated by a reversal of the field orientation.     

Visible Light Photocatalysis of 6π Heterocyclization

Photo‐mediated 6π cyclization is a valuable method for the formation of fused heterocyclic systems. Here we demonstrate that irradiation of cyclic 2‐aryloxyketones with blue LED light in the presence of an Ir^III complex leads to efficient and high yielding arylation across a panoply of substrates by energy transfer. 2‐Arylthioketones and 2‐arylaminoketones also cyclize effectively under these conditions. Quantum calculation demonstrates that the reaction proceeds via conrotatory ring closure in the triplet excited state. Subsequent suprafacial 1,4‐hydrogen shift and epimerization leads to the observed cis‐fused products.     

Asian Hornet,Vespa velutina Lepeletier 1836 (Hym.: Vespidae), Venom Obtention Based on an Electric Stimulation Protocol

The yellow-legged Asian hornet (Vespa velutina Lepeletier 1836 (Hymenoptera: Vespidae)) is naturally distributed in China, Southeast Asia, and India; however, recently it has been detected outside of its native area, confirmed as being established in South Korea, Europe, and Japan. Health risks and deaths caused by the invasive Vespa velutina stings have become a public health concern, being the most common cause of anaphylaxis due to hymenopterans in some European regions. This in turn has led to increased demand from medical practitioners and researchers for Vespa velutina venom for diagnostic and therapeutic purposes. In this study, a straightforward, quick, and inexpensive method for obtaining Vespa velutina venom by electric stimulation is described. The venom extracts were analyzed by nuclear magnetic resonance spectroscopy (¹H-NMR). The availability of Vespa velutina venom will lead to improved diagnostic and therapeutic methods, mainly by venom immunotherapy (VIT), in patients allergic to this invasive species.     

Dielectric Relaxation Phenomena and Electric Properties of Conductive Composite Polyurethane/Polyaniline Films

Summary: Composite polyurethane/polyaniline (PU/PANI) films have been chemically prepared by oxidative in-situ polymerization of aniline inside the previously swelled PU film. Swelling kinetic studies have shown that for PU films the swelling degree of aniline is 25 wt.%. The dielectric and electrical properties of the composite films were measured using dielectric relaxation spectroscopy and four-probe method. Dielectric measurements as a function of temperature and frequency revealed the presence of a relaxation process for the composite PU/PANI-HCl film. This relaxation was explained in terms of interfacial polarization due to the double-layered structure of the composite film. The activation energy values found by dielectric and electrical measurements are close and this result confirms the conducting character of the PANI containing layer.     

Small Molecule Fisetin Modulates Alpha–Synuclein Aggregation

Phenolic compounds are thought to be important to prevent neurodegenerative diseases (ND). Parkinson’s Disease (PD) is a neurodegenerative disorder known for its typical motor features, the deposition of α-synuclein (αsyn)-positive inclusions in the brain, and for concomitant cellular pathologies that include oxidative stress and neuroinflammation. Neuroprotective activity of fisetin, a dietary flavonoid, was evaluated against main hallmarks of PD in relevant cellular models. At physiologically relevant concentrations, fisetin protected SH-SY5Y cells against oxidative stress overtaken by tert-butyl hydroperoxide (t-BHP) and against methyl-4-phenylpyridinuim (MPP⁺)-induced toxicity in dopaminergic neurons, the differentiated Lund human Mesencephalic (LUHMES) cells. In this cellular model, fisetin promotes the increase of the levels of dopamine transporter. Remarkably, fisetin reduced the percentage of cells containing αsyn inclusions as well as their size and subcellular localization in a yeast model of αsyn aggregation. Overall, our data show that fisetin exerts modulatory activities toward common cellular pathologies present in PD; remarkably, it modulates αsyn aggregation, supporting the idea that diets rich in this compound may prove beneficial.     

Structural Heterogeneity of Cryotrapped Intermediates in the Bacterial Blue Light Photoreceptor,Photoactive Yellow Protein¶

We investigate by X‐ray crystallographic techniques the cryotrapped states that accumulate on controlled illumination of the blue light photoreceptor, photoactive yellow protein (PYP), at 110 K in both the wild‐type species and its E46Q mutant. These states are related to those that occur during the chromophore isomerization process in the PYP photocycle at room temperature. The structures present in such states were determined at high resolution, 0.95–1.05Å. In both wild type and mutant PYP, the cryotrapped state is not composed of a single, quasitransition state structure but rather of a heterogeneous mixture of three species in addition to the ground state structure. We identify and refine these three photoactivated species under the assumption that the structural changes are limited to simple isomerization events of the chromophore that otherwise retains chemical bonding similar to that in the ground state. The refined chromophore models are essentially identical in the wild type and the E46Q mutant, which implies that the early stages of their photocycle mechanisms are the same.     

Sol‐Gel Synthesis and Photocatalytic Study of Visible Light Active N‐Doped KSbWO6

KSbWO₆ was prepared by sol‐gel method. N‐doped KSbWO₆ (KSbWO_6–xN_x) was obtained by heating KSbWO₆ and urea at 400 °C. Both the compounds are characterized by powder X‐ray diffraction (XRD), TEM, SEM‐EDS, X‐ray photo electronic spectroscopy (XPS), and UV/Vis diffuse reflectance spectroscopy (UV‐DRS). A shift in the peak positions of powder XRD and XPS spectra was observed. The band gap energy (E_g) of KSbWO₆ and N‐doped KSbWO₆ was obtained from their diffused reflectance spectra.E_g was reduced from 3.17 eV to 2.56 eV upon nitrogen doping in KSbWO₆. The reduction of the E_g is attributed to the lifting of valence band of N‐doped KSbWO₆, due to the mixing of O 2p states with N 2p states. The photocatalytic activity of both the samples was studied by degradation of methylene blue (MB). The nitrogen doped KSbWO₆ shows higher photocatalytic activity compared to that of KSbWO₆.     

Percolative Phenomena in Microemulsions of the ‘One-Component Macrofluid’ Type

The temperature dependence of the water self-diffusion coefficients (D), as well as those of low- and high-field (stationary and time-dependent) specific conductivities (K), have been determined in the percolation regime of ternary mixtures of water, AOT, and oil. For the first time a pronounced similarity in the behavior of D and κ was detected giving instructive hints about the large variations in the specific conductivities of these systems. Results from kinetic and stationary experiments are consistent with a network-structure model of micro phases in the percolation regime in which the micro phases retain their discrete character.     

Ag@Bi2WO6Composites with High Visible‐Light‐Driven Photocatalytic Activities Prepared in UV Light Irradiation

Bi₂WO₆ microstructures were synthesized through hydrothermal process and Ag@Bi₂WO₆ composites were synthesized by simple UV light irradiation for 5 min using Bi₂WO₆ and AgNO₃ as raw materials. Ag@Bi₂WO₆ composites were characterized by X‐ray powder diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), and UV‐Vis absorption spectrum (UV‐Vis). Few Ag deposited on the Bi₂WO₆ leads to an increase in photocatalytic activity, which clearly indicates that the recombination of photogenerated charge carrier between the hybrid orbital of Bi6s and O2p (valence band) to the empty W5d orbital is inhibited greatly in the Ag@Bi₂WO₆ composite. In addition, a few H₂O₂ will greatly enhance photocatalytic activity of Ag@Bi₂WO₆, and the proper reason is discussed.     

Electroosmotic Phenomena in Fractures

Electroosmotic phenomena in fractures have been investigated in the linear limit for various double-layer thicknesses. The effects of the geometrical parameters were systematically studied for deterministic sinusoidal and random self-affine fractures. The numerical results show a definite influence of the surface amplitude on electroosmotic processes. For self-affine fractures, the roughness or Hurst exponent has a much larger incidence than the correlation parameter between the two surfaces. All the electroosmotic coupling coefficients can be gathered in a single relationship which depends on a characteristic length scale Lambda, applicable to every configuration. Such a length was already found useful for porous media, but the relationship is different. Copyright 2000 Academic Press.     

Low Level Light Therapy Modulates Inflammatory Mediators Secreted by Human Annulus Fibrosus Cells during Intervertebral Disc Degeneration In Vitro

Intervertebral disc degeneration (IVD) is one of the important causes of low back pain and is associated with inflammation induced by interaction between macrophages and the human annulus fibrosus (AF) cells. Low‐level light therapy (LLLT) has been widely known to regulate inflammatory reaction. However, the effect of LLLT on macrophage‐mediated inflammation in the AF cells has not been studied till date. The aim of this study is to mimic the inflammatory microenvironment and to investigate the anti‐inflammatory effect of LLLT at a range of wavelengths (405, 532 and 650 nm) on the AF treated with macrophage‐like THP‐1 cells conditioned medium (MCM) containing proinflammatory cytokines and chemokines (interleukin‐1beta, tumor necrosis factor‐alpha, interleukin‐6 and 8). We observed that AF cells exposed to MCM secrete significantly higher concentrations of IL‐6, IL‐8, IL‐1β and TNF‐α. LLLT markedly inhibited secretion of IL‐6 at 405 nm in a time‐dependent manner. Level of IL‐8 was significantly decreased at all wavelengths in a time‐dependent manner. We showed that MCM can induce the inflammatory microenvironment in AF cells and LLLT selectively suppressed IL‐6 and 8 levels. The results indicate that LLLT is a potential method of IVD treatment and provide insights into further investigation of its anti‐inflammation effect on IVD.     

New Phenomena in Radical Polymerization

G. Smets, Louvain, Belqium: Gentlemen, as Professor Vogl already said, Professor Zubov willpresent today the paper which should have been presented by our colleague, Professor Kabanov. Each of us knows very well the very active research directed by Professor Kabanov at the Lomonosov University of Moscow. We do regret very sincerely his absence. May I now ask, please, Professor Zubov to take the chair.     

Transport Phenomena in Nanoporous Materials

Diffusion, that is, the irregular movement of atoms and molecules, is a universal phenomenon of mass transfer occurring in all states of matter. It is of equal importance for fundamental research and technological applications. The present review deals with the challenges of the reliable observation of these phenomena in nanoporous materials. Starting with a survey of the different variants of diffusion measurement, it highlights the potentials of “microscopic” techniques, notably the pulsed field gradient (PFG) technique of NMR and the techniques of microimaging by interference microscopy (IFM) and IR microscopy (IRM). Considering ensembles of guest molecules, these techniques are able to directly record mass transfer phenomena over distances of typically micrometers. Their concerted application has given rise to the clarification of long‐standing discrepancies, notably between microscopic equilibrium and macroscopic non‐equilibrium measurements, and to a wealth of new information about molecular transport under confinement, hitherto often inaccessible and sometimes even unimaginable.