Suchergebnisse

1. Biological, Photochemical, and Spectroscopic Applications of Lasers -- 2. Photochemistry of the Nucleic Acids -- 3. Ultraviolet Radiation Effects on the Human Eye -- 4. Lethal and Mutagenic Effects of Near-Ultraviolet Radiation -- 5. DNA Repair Enzymes in Mammalian Cells.

Polysaccharides, TEP, photochemistry, hydrogen peroxide, iron, ligand, electrochemistry, voltammetry, biogeochemistry, complexation. - In large areas of the ocean, the so called high nutrient low chlorophyll (HNLC) areas, phytoplankton growth is partly limited by depleted iron (Fe) conditions due to very low Fe input to surface waters. Fe is an important nutrient for marine phytoplankton, being essential in many metabolic reactions. Fast hydrolysis and scavenging onto particles constantly remove Fe from the surface ocean. More than 99% of the remaining dissolved Fe is found to be bound by organic compounds. Photochemical reactions involving dissolved organic matter (DOM) and oxygen form hydrogen peroxide (HOOH). HOOH acts as strong oxidant or reductant in the cycling of organic compounds and trace metals like Fe. The objective of this PhD project was to investigate the role of acidic polysaccharides, main constituents of phytoplankton exudates, on the redox photochemistry of Fe and as Fe ligands.

Metallacarboranes with the shape of the Greek letter 8, such as [Co(C2B9H11)2]@, were tested, for the first time, as efficient photoredox catalysts in the oxidation of aromatic and aliphatic alcohols in water. Their efficiency is linked to their high solubility in water, their high oxidizing power (Co4+/3+), and their absence of fluorescence on excitation, among others. In most of the studied examples, using a catalyst load of 0.4 mol% gave high yields of 90-95% with selectivity greater than 99%. By reducing the catalyst load to 0.01 mol%, quantitative conversion of reactants to products was achieved, in some cases with greater than 99% yield, high catalyst efficiency reaching a turnover number of 10 000, and a higher yield with a 45 times lower concentration of catalyst. The metallacarboranes can be recovered easily by precipitation on addition of [NMe4]Cl. A pathway for the photoredox-catalyzed oxidation of alcohols is proposed ; This research has been financed by MINECO (CTQ2016-75150-R and CTQ2015-66143-P) and Generalitat de Catalunya (2017 SGR 1720).Severo Ochoa" Program for Centers of Excellence in R&D 234 (SEV-2015-0496) is appreciated. We gladly thank the CESCA, the Supercomputing Center of Catalonia, for providing us with access to their computers. Z.K. is grateful for the general support of the European Union's Horizon 2020 research and innovation program under the Marie SkłodowskaCurie grant agreement MSCA-IF-2016–751587

Cyclotides are small cyclic polypeptides found in a variety of organisms, ranging from bacteria to plants. Their ring structure endows those polypeptides with specific properties, such as improved stability against enzymatic degradation. Optimal cyclotide activity is often observed only in the presence of intra-ring disulfide bonds. Synthesis of soft nano-objects mimicking the conformation of natural cyclotides remains challenging. Here, a new class of natural cyclotide mimics synthesized by a stepwise folding-activation-collapse process at high dilution starting from simple synthetic precursor polymers is established. The initial folding step is carried out by a photoactivated hetero Diels-Alder (HDA) ring-closing reaction, which is accompanied by chain compaction of the individual precursor polymer chains as determined by size exclusion chromatography (SEC). The subsequent activation step comprises a simple azidation procedure, whereas the final collapse step is driven by CuAAC in the presence of an external cross-linker, providing additional compaction to the final single-ring nanoparticles (SRNPs). The unique structure and compaction degree of the SRNPs is established via a detailed comparison with conventional single-chain nanoparticles (SCNPs) prepared exclusively by chain collapse from the exact same precursor polymer (without the prefolding step). The stepwise folding-activation-collapse approach opens new avenues for the preparation of artificial cyclotide mimetics. ; Financial support by the Spanish Ministry "Ministerio de Economia y Competitividad", MAT2015-63704-P (MINECO/ FEDER, UE), the Basque Government, IT-654-13, and the Gipuzkoako Foru Aldundia, RED 101/17, is acknowledged. J.R.-C. thanks the Materials Physics Center – MPC for support (mobility and Ph.D. grants). C.B.-K. acknowledges the Australian Research Council (ARC) in the context of a Laureate Fellowship, enabling his photochemical research program. H.F. acknowledges generous funding from the German National Academy of Science, Leopoldina. ; Peer reviewed

This work pioneers the design of visible (415 nm) and UV-B light (300 nm) reactive nanoparticles via radical polymerization in aqueous heterogeneous media based on methyl methacrylate (MMA) and unique acrylates bearing tetrazole functionalities in a simple and straightforward two step reaction. Stable colloidal nanoparticles with an average diameter of 150 nm and inherent tetrazole functionality (varying from 2.5 to 10 wt% relative to MMA) are prepared via one-pot miniemulsion polymerization. In a subsequent step, fluorescent pyrazoline moieties serving as linkage points are generated on the nanoparticles by either photoinduced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC) or nitrile imine carboxylic acid ligation (NICAL) in water, thus enabling the particles as fluorescent tracers. Through in-depth molecular surface analysis, it is demonstrated that the photoreactive nanoparticles undergo ligation to a variety of substrates bearing functionalities including maleimides, acrylates, or carboxylic acids, illustrating the versatility of the particle modification process. Critically, the unique ability of the photoreactive nanoparticles to be activated with visible light allows for their decoration with UV light-sensitive molecules. Herein, the ligation of folic acida vitamin prone to degradation under UV light-to the photoreactive nanoparticles using visible light is exemplified, demonstrating the synthetic power of our photoreactive fluorescent nanoparticle platform technology. ; L.D. and N.Z. contributed equally to this work. C.B.-K. acknowledges the Australian Research Council (ARC) for funding in the form of a Laureate Fellowship underpinning his photochemical research program as well as the Queensland University of Technology (QUT) for key continued support. N.Z. is grateful for the funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement no. 665501 with the research Foundation Flanders (FWO). The XPS data of the latexes after the NICAL or NITEC reactions reported herein were obtained at the Central Analytical Research Facility (CARF) operated by the Institute for Future Environments (IFE). Access to CARF is supported by generous funding from the Science and Engineering Faculty (SEF).

EZ-C acknowledges the University of St Andrews and EPSRC (EP/M02105X/1) for financial support. DE thanks funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 700961. DJ acknowledges the European Research Council (Marches grant n°278845) and the RFI Lumomat for financial support. ; Synthetic self-assembly is a powerful technique for the bottom-up construction of discrete and well-defined polyhedral nanostructures resembling the spherical shape of large biological systems. In recent years, numerous Archimedean-shaped coordination cages have been reported based on the assembly of bent monodentate organic ligands containing two or more distal pyridyl rings and square planar PdII ions. The formation of photoactive PdII metallamacrocycles and cages, however, remain rare. Here we report the first examples of emissive and homochiral supramolecular cages of the form of [Ir8Pd4]16+. These cages provide a suitably sized cavity to host large guest molecules. Importantly, encapsulation and energy transfer have been observed between the blue-emitting NBu4[Ir(dFppy)2(CN)2] guest and the red-emitting Δ8-[Ir8Pd4]16+ cage. ; Publisher PDF ; Peer reviewed

This fact-sheet by the EPA defines and describes the functions of the Community Multi-scale Air Quality Modeling System (CMAQ).

[EN] Solid niobium oxides (Nb2O5 center dot nH(2)O) and niobium phosphate were used as heterogeneous acid catalysts to promote the condensation between a switchable oxazine and a fluorescent coumarin in an aprotic solvent. The catalysts were found to promote the generation of an active methylene from the enamine-based portion of the oxazine, which was followed by a nucleophilic attack on the aldehyde functionality of the coumarin reagent. In the resulting system, the emission of the conjugated fluorophore can be observed at 670 nm and, thus, the processes occurring at the catalyst surface can be monitored in real time by total internal reflection fluorescence microscopy (TIRFM). ; The authors wish to thank the Natural Sciences and Engineering Research Council (NSERC) and the Canada Research Chairs program. The University of Ottawa International Office provided grants to study niobium. Thanks are due to the Government of Canada and NSERC for a Banting Postdoctoral Fellowship to S. Impellizzeri and a Vanier Scholarship to C. Fasciani. S. Simoncelli acknowledges a DFAIT fellowship from ELAP (Emerging Leaders in the Americas Program) to support her visit to Canada. M. L. Marin thanks the financial support of the Generalitat Valenciana (BEST/2012/233) and the Distinguished Visiting Professor program of the University of Ottawa. We thank Dr. Jose-Carlos Netto-Ferreira of INMETRO (Rio de Janeiro, Brazil) for providing chemicals from CBMM. ; Impellizzeri, S.; Simoncelli, S.; Fasciani, C.; Marín García, ML.; Hallett-Tapley, GL.; Hodgson, GK.; Scaiano, JC. (2015). Mechanistic insights into the Nb2O5 and niobium phosphate catalyzed in situ condensation of a fluorescent halochromic assembly. Catalysis Science and Technology. 5(1):169-175. https://doi.org/10.1039/C4CY00703D ; S ; 169 ; 175 ; 5 ; 1

A new mechanism of photosensitized formation of thymine (Thy) dimers is proposed, which involves generation of a delocalized triplet excited state as the key step. This is supported by chemical evidence obtained by combining one benzophenone and two Thy units with different degrees of freedom, whereby the photoreactivity is switched from a clean Paterno-Buchi reaction to a fully chemo-, regio-, and stereoselective [2+2] cycloaddition. ; Financial support from the Spanish Government (Grants SEV-2012-0267, CTQ2012-38754-C03-03, and CTQ2012-32621), Generalitat Valenciana (Prometeo Program), and Technical University of Valencia (Predoctoral FPI fellowship for P.M.) is gratefully acknowledged. ; Miró Richart, P.; Lhiaubet, VL.; Marín García, ML.; Miranda Alonso, MÁ. (2015). Photosensitized Thymine Dimerization via Delocalized Triplet Excited States. Chemistry - A European Journal. 21(47):17051-17056. doi:10.1002/chem.201502719 ; S ; 17051 ; 17056 ; 21 ; 47

This study focuses on the daily and seasonal variability of particle number size distributions and concentrations, performed at the Montseny (MSY) regional background station in the western Mediterranean from October 2010 to June 2011. Particle number concentrations at MSY were shown to be within range of various other sites across Europe reported in literature, but the seasonality of the particle number size distributions revealed significant differences. The Aitken mode is the dominant particle mode at MSY, with arithmetic mean concentrations of 1698 cm3, followed by the accumulation mode (877 cm-3) and the nucleation mode (246 cm-3). Concentrations showed a strong seasonal variability with large increases in particle number concentrations observed from the colder to warmer months. The modality of median size distributions was typically bimodal, except under polluted conditions when the size distribution was unimodal. During the colder months, the daily variation of particle number size distributions are strongly influenced by a diurnal breeze system, whereby the Aitken and accumulation modes vary similarly to PM1 and BC mass concentrations, with nocturnal minima and sharp day-time increases owing to the development of a diurnal mountain breeze. Under clean air conditions, high levels of nucleation and lower Aitken mode concentrations were measured, highlighting the importance of new particle formation as a source of particles in the absence of a significant condensation sink. During the warmer months, nucleation mode concentrations were observed to be relatively elevated both under polluted and clean conditions due to increased photochemical reactions, with enhanced subsequent growth owing to elevated concentrations of condensable organic vapours produced from biogenic volatile organic compounds, indicating that nucleation at MSY does not exclusively occur under clean air conditions. Finally, mixing of air masses between polluted and non-polluted boundary layer air, and brief changes in the air mass being sampled gave rise to unusual particle number size distributions, with specific cases of such behaviour discussed at length. ; This study was supported by the Ministry of Economy and Competitiveness and FEDER funds under the projects CARIATI (CGL2008-06294/CLI), VAMOS (CGL2010 19464/CLI) and GRACCIE (CSD 2007-00067), and from the Generalitat de Catalunya 2009 SGR8. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/ 2007-2013) ACTRIS under grant agreement no. 262254. The authors would like to extend their gratitude to Jesu´ s Parga and Jordi Gil for their technical support. The authors also thank METEOCAT for the meteorological data and the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website (http://www.arl.noaa.gov/ ready.html) used in this publication. ; Peer reviewed

1 Phototechnology and Biological Experimentation -- 2 Spectroscopy -- 3 Photochemistry -- 4 Photosensitization -- 5 Ultraviolet Radiation Effects On Molecules and Cells -- 6 Environmental Photobiology -- 7 Photomedicine -- 8 Chronobiology (Circadian Rhythms) -- 9 Extraretinal Photoreception -- 10 Vision -- 11 Photomorphogenesis -- 12 Photomovement -- 13 Photosynthesis -- 14 Bioluminescence -- 15 New Topics in Photobiology.

The use of legal and illicit drugs is widespread in Australia, however for a significant number of people, substance use can lead to addiction, also known as dependence. Many people become dependent on a drug, and they feel that they cannot function without it. They may spend a lot of their time and energy finding and using the drug. They may also need to take increasing amounts to get the same effects, and experience withdrawal symptoms when they stop using it. Addiction is a physical and/or psychological need to use a substance; some substances are more addictive than others, and some users

In this work, the luminescence properties of new materials based on open-shell molecular systems are studied. In particular, we prepared polymeric films and organic nanoparticles (ONPs) doped with triphenylmethyl radical molecules. ONPs exhibit a uniform size distribution, spherical morphology and high colloidal stability. The emission spectrum of low-doped ONP suspensions and low-doped films is very similar to the emission spectrum of TTM in solution, while the luminescence lifetime and the luminescence quantum yield (LQY) are highly increased. Increasing the radical doping leads to a progressive decrease of the LQY and the appearance of a new broad excimeric band at longer wavelengths, both for ONPs and films. Thus, not only the luminescence properties were improved, but also the formation of excimers from stable and persistent supramolecular radical-pairs was observed for the first time. The good stability and luminescence properties with emission in the red-NIR region (650–800 nm), together with the open-shell nature of the emitter, make these free-radical excimer-forming materials promising candidates for optoelectronic and bioimaging applications. ; The research leading to these results received funding from the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme FP7/2007–2013 under a REA grant agreement no. 607721 (ITN Nano2Fun). A DGI grant (BeWell; CTQ2013-40480-R and Dynamo MAT2013-50036-EXP), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), the Generalitat de Catalunya (grant 2014-SGR-17) are also acknowledged. ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the "Severo Ochoa" Programme for Centres of Excellence in R&D (SEV-2015-0496). This work has been developed inside the Materials Science PhD programs of Universitat Autonoma de Barcelona and of University of Parma. ; Peer reviewed