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https://www.readbyqxmd.com/read/28326554/chlamydomonas-reinhardtii-responding-to-high-light-a-role-for-2-propenal-acrolein
#1
Thomas Roach, Theresa Baur, Wolfgang Stöggl, Anja Krieger-Liszkay
High light causes photosystem II to generate singlet oxygen ((1) O2 ), a reactive oxygen species (ROS) that can react with membrane lipids, releasing reactive electrophile species (RES), such as acrolein. To investigate how RES may contribute to light stress responses, Chlamydomonas reinhardtii was high light-treated in photoautotrophic and mixotrophic conditions and also in an oxygen-enriched atmosphere to elevate ROS production. The responses were compared to exogenous acrolein. Non-photochemical quenching (NPQ) was higher in photoautotrophic cells, as a consequence of a more de-epoxidized state of the xanthophyll cycle pool and more LHCSR3 protein, showing that photosynthesis was under more pressure than in mixotrophic cells...
March 21, 2017: Physiologia Plantarum
https://www.readbyqxmd.com/read/28323378/photochemical-generation-of-strained-cycloalkynes-from-methylenecyclopropanes
#2
Daniel P Maurer, Rui Fan, Dasan M Thamattoor
The hydrocarbons 1-cyclopentylidene-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene and 1-cyclobutylidene-1a,9b-dihydro-1H-cyclopropa[l]phenanthrene undergo photolysis in solution at ambient temperature to produce cyclohexyne and cyclopentyne, respectively. These strained cycloalkynes, formed via the putative cycloalkylidenecarbenes, were intercepted as Diels-Alder adducts. Calculations at the CCSD(T)/cc-pVTZ//B3LYP/6-31+G* level of theory show that singlet cyclopentylidenecarbene has to overcome a barrier of 9...
March 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28323367/enantioselective-formal-%C3%AE-methylation-and-%C3%AE-benzylation-of-aldehydes-by-means-of-photo-organocatalysis
#3
Giacomo Filippini, Mattia Silvi, Paolo Melchiorre
Detailed herein is the photochemical organocatalytic enantioselective α-alkylation of aldehydes with (phenylsulfonyl)alkyl iodides. The chemistry relies on the direct photoexcitation of enamines to trigger the formation of reactive carbon-centered radicals from iodosulfones, while the ground-state chiral enamines provide effective stereochemical control over the radical trapping process. The phenylsulfonyl moiety, acting as a redox auxiliary group, facilitates the generation of radicals. In addition, it can eventually be removed under mild reducing conditions to reveal methyl and benzyl groups...
March 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28322264/plasmon-assisted-site-selective-growth-of-ag-nanotriangles-and-ag-cu2o-hybrids
#4
Ying Xie, Liang Ma, Zi-Qiang Cheng, Da-Jie Yang, Li Zhou, Zhong-Hua Hao, Qu-Quan Wang
We report a plasmon-assisted growth of metal and semiconductor onto the tips of Ag nanotriangles (AgNTs) under light irradiation. The site-selective growth of Ag onto AgNTs are firstly demonstrated on the copper grids and amine-coated glass slides. As the irradiation time increases, microscopic images indicate that AgNTs gradually touch with each other and finally "weld" tip-to-tip together into the branched chains. Meanwhile, the redshift of plasmon band is observed in the extinction spectra, which agrees well the growth at the tips of AgNTs and the decrease of the gaps between the adjacent nanotriangles...
March 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28322089/biological-changes-of-green-pea-pisum-sativum-l-by-selenium-enrichment
#5
Farzaneh Garousi, Béla Kovács, Éva Domokos-Szabolcsy, Szilvia Veres
Supplement of common fertilizers with selenium (Se) for crop production will be an effective way to produce selenium-rich food and feed. The value of green pea seeds and forages as alternative protein source can be improved by using agronomic biofortification. Therefore, biological changes of green pea (Pisum sativum L.) and influences of inorganic forms of Se (sodium selenite and sodium selenate) at different concentrations on the accumulation of magnesium (Mg) and phosphorus (P) were investigated in greenhouse experiment...
March 2017: Acta Biologica Hungarica
https://www.readbyqxmd.com/read/28322053/development-of-a-novel-lysosome-targeted-ruthenium-ii-complex-for-phosphorescence-time-gated-luminescence-assay-of-biothiols
#6
Quankun Gao, Wenzhu Zhang, Bo Song, Run Zhang, Weihua Guo, Jingli Yuan
Considering the important roles of biothiols in lysosomes of live organisms, and unique photophysical/photochemical prop-erties of ruthenium(II) complexes, a novel ruthenium(II) complex, Ru-2, has been developed as a molecular probe for phosphorescence and time-gated luminescence assay of biothiols in human sera, live cells and in vivo. Ru-2 is weakly lumi-nescent due to the effective photo-induced electron transfer (PET) from Ru(II) luminophore to electron acceptor, 2,4-dinitrobenzene-sulfonyl (DNBS). In the presence of biothiols, such as glutathione (GSH), cysteine (Cys) and homocysteine (Hcy), the emission of Ru-2 solution was switched ON, as the result of the cleavage of quencher to form the production, Ru-1...
March 21, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28320948/highly-oriented-photosynthetic-reaction-centers-generate-a-proton-gradient-in-synthetic-protocells
#7
Emiliano Altamura, Francesco Milano, Roberto R Tangorra, Massimo Trotta, Omar Hassan Omar, Pasquale Stano, Fabio Mavelli
Photosynthesis is responsible for the photochemical conversion of light into the chemical energy that fuels the planet Earth. The photochemical core of this process in all photosynthetic organisms is a transmembrane protein called the reaction center. In purple photosynthetic bacteria a simple version of this photoenzyme catalyzes the reduction of a quinone molecule, accompanied by the uptake of two protons from the cytoplasm. This results in the establishment of a proton concentration gradient across the lipid membrane, which can be ultimately harnessed to synthesize ATP...
March 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28320865/9-cis-neoxanthin-in-lhcii-regulates-the-binding-of-violaxanthin-and-xanthophyll-cycle
#8
Ke Wang, Wenfeng Tu, Cheng Liu, Yan Rao, Zhimin Gao, Chunhong Yang
The light harvesting chlorophyll (Chl) a/b complex of photosystem II (LHCII) is able to switch to multiple functions under different light conditions, i.e. harvesting solar energy for photosynthesis and dissipating excess excitation energy for photoprotection. The role of the different carotenoids (Cars) bound to LHCII in regulating the structure and function of the complex is a long-lasting question in photosynthesis research. 9-cis-neoxanthin (Nx) is one of the important Cars, which can only be found in the light harvesting Chla/b complexes of photosystem II...
March 20, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28320288/analysis-of-photoprotection-and-apparent-non-photochemical-quenching-of-chlorophyll-fluorescence-in-tradescantia-leaves-based-on-the-rate-of-irradiance-induced-changes-in-optical-transparence
#9
V V Ptushenko, O S Ptushenko, O P Samoilova, A E Solovchenko
The kinetics of irradiation-induced changes in leaf optical transparence (ΔT) and non-photochemical quenching (NPQ) of chlorophyll fluorescence in Tradescantia fluminensis and T. sillamontana leaves adapted to different irradiance in nature was analyzed. Characteristic times of a photoinduced increase and a dark decline of ΔT in these species were 12 and 20 min, respectively. The ΔT was not confirmed to be the main contributor to the observed middle phase of NPQ relaxation kinetics (τ = 10-28 min). Comparison of rate of photoinduced increase in ΔT and photosystem II quantum yield recovery showed that the former did not affect the tolerance of the photosynthetic apparatus (PSA) to irradiances up to 150 µmol PAR·m(-2)·s(-1)...
January 2017: Biochemistry. Biokhimii︠a︡
https://www.readbyqxmd.com/read/28319888/heterogeneous-reaction-of-peroxyacetyl-nitrate-pan-on-soot
#10
Ximeng Zhao, Tianyu Gao, Jianbo Zhang
The interaction between photochemical oxidants and aerosol particles has been examined in previous atmospheric pollution studies. The heterogeneous reaction can affect the concentration of gases and free radicals, as well as the morphology and properties of particles. In this report, the interaction between the photochemical oxidant peroxyacetyl nitrate (PAN) and soot particles was investigated using a flow tube system. We used real-time online monitoring equipment to track changes in PAN concentrations. Substances on the soot surface were detected using ion chromatography (IC), x-ray photoelectron spectroscopy (XPS), and other surface analysis methods...
March 6, 2017: Chemosphere
https://www.readbyqxmd.com/read/28319705/contributions-of-vehicular-emissions-and-secondary-formation-to-nitrous-acid-concentrations-in-ambient-urban-air-in-tokyo-in-the-winter
#11
Yoshihiro Nakashima, Yasuhiro Sadanaga, Shinji Saito, Junya Hoshi, Hiroyuki Ueno
Nitrous acid (HONO) plays an important role in the formation of OH radicals, which are involved in photochemical oxidation. HONO concentrations in ambient air at urban sites have previously been measured, but very few studies have been performed in central Tokyo. In this study, HONO concentrations in ambient air in southeast central Tokyo (near Tokyo Bay) in winter were determined by incoherent cavity enhanced absorption spectroscopy. The O3, NO, NO2, and SO2 concentrations were simultaneously determined. The NO concentrations were used to classify the parts of the study period into types I (high pollution), II (medium pollution), and III (low pollution)...
March 15, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28319399/monitoring-photochemical-reactions-using-marangoni-flows
#12
Joost Muller, Hubertus M J M Wedershoven, Anton A Darhuber
We evaluated the sensitivity and time-resolution of a technique for photochemical reaction monitoring based on interferometric detection of the deformation of liquid films. The reaction products change the local surface tension and induce a Marangoni flow in the liquid film. As a model system, we consider the irradiation of the aliphatic hydrocarbon squalane with broadband deep-UV light. We developed a numerical model that quantitatively reproduces the flow patterns observed in the experiments. Moreover, we present self-similarity solutions that elucidate the mechanisms governing different stages of the dynamics and their parametric dependence...
March 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28319302/br%C3%A3-nsted-acid-catalysis-in-visible-light-induced-2-2-%C3%A2-photocycloaddition-reactions-of-enone-dithianes
#13
Christoph Brenninger, Alexander Pöthig, Thorsten Bach
1,3-Dithiane-protected enones (enone dithianes) were found to undergo an intramolecular [2+2] photocycloaddition under visible-light irradiation (λ=405 nm) in the presence of a Brønsted acid (7.5-10 mol %). Key to the success of the reaction is presumably the formation of colored thionium ions, which are intermediates of the catalytic cycle. Cyclobutanes were thus obtained in very good yields (78-90 %). It is also shown that the dithiane moiety can be reductively or oxidatively removed without affecting the photochemically constructed ring skeleton...
March 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28319223/kinetics-and-heterogeneity-of-energy-transfer-from-light-harvesting-complex-ii-to-photosystem-i-in-the-supercomplex-isolated-from-arabidopsis
#14
Stefano Santabarbara, Tania Tibiletti, William Remelli, Stefano Caffarri
State transitions are a phenomenon that maintains the excitation balance between photosystem II (PSII) and photosystem I (PSI-LHCI) by controlling their relative absorption cross-sections. Under light conditions exciting PSII preferentially, a trimeric LHCII antenna moves from PSII to PSI-LHCI to form the PSI-LHCI-LHCII supercomplex. In this work, the excited state dynamics in the PSI-LHCI and PSI-LHCI-LHCII supercomplexes isolated from Arabidopsis have been investigated by picosecond time-resolved fluorescence spectroscopy...
March 20, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28318253/aminyl-radical-generation-via-tandem-norrish-type-i-photocleavage-%C3%AE-fragmentation-independent-generation-and-reactivity-of-the-2-deoxyadenosin-n6-yl-radical
#15
Liwei Zheng, Markus Griesser, Derek A Pratt, Marc M Greenberg
Formal hydrogen atom abstraction from the nitrogen-hydrogen bonds in purine nucleosides produces reactive intermediates that are important in nucleic acid oxidation. Herein we describe an approach for the independent generation of the purine radical resulting from hydrogen atom abstraction from the N6-amine of 2'-deoxyadenosine (dA•). The method involves sequential Norrish Type I photocleavage of a ketone (7b) and β-fragmentation of the initially formed alkyl radical (8b) to form dA• and acetone. The formation of dA• was followed by laser flash photolysis, which yields a transient with λmax ≈ 340 nm and a broader weaker absorption centered at ∼560 nm...
March 20, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28317777/preparation-characterization-and-stability-of-curcumin-loaded-zein-shellac-composite-colloidal-particles
#16
Cuixia Sun, Chenqi Xu, Like Mao, Di Wang, Jie Yang, Yanxiang Gao
Curcumin-loaded zein-shellac composite particles were prepared by the antisolvent co-precipitation method. The encapsulation efficiency of curcumin was significantly improved from 82.7% in zein particles to 93.2% in zein-shellac complex particles. The result of differential scanning calorimetry suggested that curcumin in the polymeric matrix was in an amorphous state. Fourier transform infrared spectroscopy analysis revealed that curcumin had non-covalently interacted with zein and shellac, mainly through hydrogen bonding and hydrophobic interaction...
August 1, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28317051/photochemically-assisted-fast-abiotic-oxidation-of-manganese-and-formation-of-%C3%AE-mno2-nanosheets-in-nitrate-solution
#17
Haesung Jung, Tandeep S Chadha, Doyoon Kim, Pratim Biswas, Young-Shin Jun
This study introduces a new and previously unconsidered fast abiotic formation of Mn(iv) oxides. We report photochemically assisted fast abiotic oxidation of Mn(2+) (aq) to Mn(iv) (s) by superoxide radicals generated from nitrate photolysis. This photochemical pathway generates randomly stacked layered birnessite (δ-MnO2) nanosheets.
March 20, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28315793/highlighting-the-effects-of-coumarin-on-adult-plants-of-arabidopsis-thaliana-l-heynh-by-an-integrated-omic-approach
#18
Fabrizio Araniti, Monica Scognamiglio, Angela Chambery, Rosita Russo, Assunta Esposito, Brigida D'Abrosca, Antonio Fiorentino, Antonio Lupini, Francesco Sunseri, Maria Rosa Abenavoli
In this study, the effects of the allelochemical coumarin through a metabolomic, proteomic and morpho-physiological approach in Arabidopsis adult plants (25days old) were investigated. Metabolomic analysis evidenced an increment of amino acids and a high accumulation of soluble sugars, after 6days of coumarin treatment. This effect was accompanied by a strong decrease on plant fresh and dry weights, as well as on total protein content. On the contrary, coumarin did not affect leaf number but caused a reduction in leaf area...
March 1, 2017: Journal of Plant Physiology
https://www.readbyqxmd.com/read/28304173/triggering-a-2-rotaxane-molecular-shuttle-by-a-photochemical-bond-cleavage-strategy
#19
Chuan Gao, Zhou-Lin Luan, Qi Zhang, Shun Yang, Si-Jia Rao, Da-Hui Qu, He Tian
The successful triggering of ring-shuttling motion between two stations in a [2]rotaxane is demonstrated by employing a photochemical bond-cleavage strategy. A photolabile bulk barrier is covalently introduced into two identical stations of the thread to prevent dynamic shuttling of the macrocycle, resulting in a "gated" state. Irradiation of UV light (λ = 365 nm) results in the complete removal of the bulk barrier and the balanced shuttling motion of the macrocycle, indicating an "open" state of the rotaxane...
March 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/28304018/graphene-nanobubbles-on-tio2-for-in-operando-electron-spectroscopy-of-liquid-phase-chemistry
#20
S Nappini, A Matruglio, D Naumenko, S Dal Zilio, F Bondino, M Lazzarino, E Magnano
X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS) provide unique knowledge on the electronic structure and chemical properties of materials. Unfortunately this information is scarce when investigating solid/liquid interfaces and chemical or photochemical reactions under ambient conditions because of the short electron inelastic mean free path (IMFP) that requires a vacuum environment, which poses serious limitation on the application of XPS and XAS to samples present in the atmosphere or in the presence of a solvent...
March 17, 2017: Nanoscale
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