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Wai L Yu, Thomas Nunns, Jeffery Richardson, Kevin I Booker-Milburn
The synthesis of two diastereomeric members of the lycorane alkaloid family is reported. Although the routes are quite different in their approach, both involve the use of photochemistry as a key step, enabling the synthesis of gram quantities in the case of β-lycorane.
February 15, 2018: Organic Letters
G M Hidy
Observations of smog over the Los Angeles Basin (LAB) links high oxidant mixing ratios with poor visibility, sometimes < 5 km. By the 1970s investigators recognized that most of the aerosol affecting visibility was from gaseous oxidation products, sulfate, nitrate and organic carbon. This led to the 1972-1973 the Aerosol Characterization Experiment (ACHEX), which included observations at the ground and from aircraft. Part of ACHEX was the measurement of smog by blimp in a Lagrangian-like format. The experiment on September 6, 1973 demonstrated that a blimp could travel with the wind across the LAB, observing ozone (O3) and precursors, and particles of different size ranges...
February 12, 2018: Journal of the Air & Waste Management Association
Nuria Pardo, M Luisa Sánchez, Zhongbo Su, Isidro A Pérez, M Angeles García
The integrated SCOPE (Soil, Canopy Observation, Photochemistry and Energy balance) model, coupling radiative transfer theory and biochemistry, was applied to a biodiesel crop grown in a Spanish agricultural area. Energy fluxes and CO2 exchange were simulated with this model for the period spanning January 2008 to October 2008. Results were compared to experimental measurements performed using eddy covariance and meteorological instrumentation. The reliability of the model was proven by simulating latent (LE) and sensible (H) heat fluxes, soil heat flux (G), and CO2 exchanges (NEE and GPP)...
January 29, 2018: Science of the Total Environment
Davide Vione, Angel Encinas, Debora Fabbri, Paola Calza
We predicted the possible direct and indirect phototransformation kinetics of carbamazepine (CBZ), ibuprofen (IBU) and diclofenac (DIC) in river water, based on data of water chemistry obtained for the Guadiana River near Badajoz (Southwestern Spain) during a year-round sampling campaign. The three compounds were chosen, (i) because they occurred at the outlet of the wastewater treatment plant (WWTP) in Badajoz, as well as in river water sampled 1 km downstream of the WWTP, and (ii) because their photochemical fate in surface waters is known well enough to be modelled...
February 3, 2018: Chemosphere
Sonal Mathur, Mahaveer P Sharma, Anjana Jajoo
In this study, pot experiments were performed to investigate the effects of high temperature stress (44 °C) in maize plants colonized with and without arbuscular mycorrhizal fungi (AMF). Various parameters characterizing photosynthetic activity were measured in order to estimate the photosynthetic efficiency in maize plants. It was observed that density of active reaction centers of PSII, quantum efficiency of photosystem II (PSII), linear electron transport, excitation energy trapping, performance index, net photosynthesis rate increased in AMF (+) plants at 44 °C ± 0...
February 4, 2018: Journal of Photochemistry and Photobiology. B, Biology
Xiang-Tian Kong, Larousse Khosravi Khorashad, Zhiming Wang, Alexander O Govorov
Chiral photochemistry remains a challenge because of the very small asymmetry in the chiro-optical absorption of molecular species. However, we think that the rapidly developing fields of plasmonic chirality and plasmon-induced circular dichroism demonstrate very strong chiro-optical effects and have the potential to facilitate the development of chiral photochemistry and other related applications such as chiral separation and sensing. In this study, we propose a new type of chiral spectroscopy - photothermal circular dichroism...
February 8, 2018: Nano Letters
Yazhen Li, Qianqian Gong, Ling Yue, Wenliang Wang, Fengyi Liu
Photochemistry of Criegee intermediates is critical in atmospheric chemistry, but it is relatively less explored compared with their thermal reactions. Using the multireference CASPT2 electronic structure calculations and CASSCF trajectory surface-hopping molecular dynamics, we have revealed a dark-state-involved A1A→X1A photoisomerization channel of the simple Criegee intermediate (CH2OO) that leads to a cyclic dioxirane. The excited molecules on A1A state, which can be either originated from B1A state via B1A→A1A internal conversion or formed by state-selectively electronic excitation, is driven by the out-of-plane motion towards a perpendicular A/X1A minimal-energy crossing point (MECI), then radiationlessly decay to the ground state with an average time constant of ~138 fs, and finally form dioxirane at ~ 254 fs...
February 8, 2018: Journal of Physical Chemistry Letters
Aurelien Trivella, Tobias Nils Wassermann, Carine Manca Tanner, Nils O B Luettschwager, Stephane Coussan
UV and IR photochemistries of malonaldehyde, the simplest molecule exhibiting an intramolecular proton exchange, have been studied in four cryogenic matrices at 4.3 K, N2, Ne, Ar and Xe. Samples have been irradiated using a UV and IR OPO type tunable laser, and with a broad band UV mercury lamp. UV and IR spectra have been recorded and compared with theoretical calculations carried out at the SAC-CI/6-31++G(d,p) (UV transitions) and B3LYP/6-311++G(2d,2p) (IR spectra) levels of theory. After de- position, the intramolecularly H-bonded form is found exclusively, while several open forms are formed upon UV irradiation...
February 8, 2018: Journal of Physical Chemistry. A
Eliot Boulanger, Jeremy N Harvey
Hybrid computational methods describing a small region of a biomolecular system with quantum mechanics and the bulk with molecular mechanics, referred to as QM/MM methods, are now a central part of computational biochemistry. This review considers developments in the QM/MM approach that make it easier to calculate free energies using accurate QM-based potential energy expressions. We also describe techniques to treat electronic coupling between the core region and the MM environment. Polarizability of the protein matrix is important but so is electronic coupling...
January 30, 2018: Current Opinion in Structural Biology
Ke-Yin Ye, Gisselle Pombar, Niankai Fu, Gregory S Sauer, Ivan Keresztes, Song Lin
The emergence of new catalytic strategies that cleverly adopt concepts and techniques frequently used in areas such as photochemistry and electrochemistry has yielded myriad new organic reactions that would be challenging to achieve using orthodox methods. Herein, we discuss the strategic use of anodically coupled electrolysis, an electrochemical process that combines two parallel oxidative events, as a complementary approach to existing methods for redox organic transformations. Specifically, we demonstrate anodically coupled electrolysis in the regio- and chemoselective chlorotrifluoromethylation of alkenes...
February 6, 2018: Journal of the American Chemical Society
Bu Duo, Lulu Cui, Zhenzhen Wang, Rui Li, Liwu Zhang, Hongbo Fu, Jianmin Chen, Huifang Zhang, A Qiong
Atmospheric pollutants including SO2, NO2, CO, O3 and inhalable particulate matter (PM2.5 and PM10) were monitored continuously from March 2014 to February 2015 to investigate characteristics of air pollution at Lhasa, Tibetan Plateau. Species exhibited similar seasonal variations except O3, with the peaks in winter but low valleys in summer. The maximum O3 concentration was observed in spring, followed by summer, autumn, and winter. The positive correlation between O3 and PM10 in spring indicated similar sources of them, and was assumed to be turbulent transport...
January 2018: Journal of Environmental Sciences (China)
Jean Cadet, Thierry Douki
UV-induced DNA damage plays a key role in the initiation phase of skin cancer. When left unrepaired or when damaged cells are not eliminated by apoptosis, DNA lesions express their mutagneic properties, leading to the activation of proto-oncogene or the inactivation of tumor suppression genes. The chemical nature and the amount of DNA damage strongly depend on the wavelength of the incident photons. The most energetic part of the solar spectrum at the Earth's surface (UVB, 280-320 nm) leads to the formation of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (64PPs)...
February 6, 2018: Photochemical & Photobiological Sciences
Shiqi Lv, Bin Yang, Yixuan Kou, Jun Zeng, Ruixiong Wang, Yumeng Xiao, Fencan Li, Ying Lu, Yuwen Mu, Changming Zhao
This study was conducted to evaluate the effects of mercury stress on growth, photosynthesis and mercury accumulation in different cultivars of a non-food energy crop, Jerusalem artichoke, and to screen appropriate cultivars for their efficacy in the phytoremediation of mercury (Hg2+) contaminated soil. Cultivars LZJ033 (high above-ground biomass and nutrient content, and strongly sexual reproduction) and LZJ119 (a long period of vegetative growth) exhibited more tolerance to mercury stress than LZJ047 (the highest tuber yield and total sugar content)...
2018: PeerJ
Benjamin J Shields, Bryan Kudisch, Gregory D Scholes, Abigail G Doyle
Here we investigate the photophysics and photochemistry of Ni(II) aryl halide complexes common to cross coupling and Ni/photoredox reactions. Computational and ultrafast spectroscopic studies reveal that these complexes feature long-lived 3MLCT excited states, implicating Ni as an underexplored alternative to precious metal photocatalysts. Moreover, we show that 3MLCT Ni(II) engages in bimolecular electron transfer with ground state Ni(II), which enables access to Ni(III) in the absence of external oxidants or photoredox catalysts...
February 5, 2018: Journal of the American Chemical Society
William L Ashley, Evan L Timpy, Thomas Charles Coombs
Nazarov reactions of 2-furyl vinyl ketones and related heteroaromatic enones, to produce furan-fused cyclopentanones using a flow photochemical approach, are described. Compounds possessing this connectivity between heterocycle and ketone (2-furyl, 2-benzofuryl, 2-thiophenyl, and 2-benzothiophenyl) have traditionally proven difficult or impossible to cyclize with typical Brønsted and Lewis acid mediated methods. Using mild flow photochemistry conditions and acetic acid (AcOH) or hexafluoroisopropanol (HFIP) as solvent, these compounds were found to cyclize in 45-97% yields, with typical UV exposure times of 3...
February 5, 2018: Journal of Organic Chemistry
Talitha Soares Pereira, Thaís Soares Pereira, Carla Leticia Figueredo de Carvalho Souza, Emilly Juliane Alvino Lima, Bruno Lemos Batista, Allan Klynger da Silva Lobato
Silicon (Si) frequently accumulates in plants tissues, mainly in roots of dicotyledons, such as cowpea. By contrast, Cadmium (Cd) is a metal that is extremely toxic to plant metabolism. This research aims to investigate if the deposition of Si in root can reduce Cd contents and minimize its negative effects on leaves, measuring gas exchange, chlorophyll fluorescence, antioxidant metabolism, photosynthetic pigments and growth, which may explain the possible role of Si in the attenuation of Cd toxicity in cowpea...
February 2018: Physiology and Molecular Biology of Plants: An International Journal of Functional Plant Biology
Martin Byrdin, Chenxi Duan, Dominique Bourgeois, Klaus Brettel
Though ubiquitously used as selective fluorescence markers in cellular biology, fluorescent proteins (FPs) still have not disclosed all of their surprising properties. One important issue, notably for single-molecule applications, is the nature of the triplet state, suggested to be the starting point for many possible photochemical reactions leading to phenomena such as blinking or bleaching. Here, we applied transient absorption spectroscopy to characterize dark states in the prototypical enhanced green fluorescent pro-tein (EGFP) of hydrozoan origin and, for comparison, in IrisFP, a representative phototransformable FP of anthozoan origin...
February 2, 2018: Journal of the American Chemical Society
Sofia Garakyaraghi, Catherine E McCusker, Saba Khan, Petr Koutnik, Anh Thy Bui, Felix N Castellano
A computationally inspired Cu(I) metal-to-ligand charge transfer (MLCT) chromophore, [Cu(sbmpep)2]+ (sbmpep = 2,9-di(sec-butyl)-3,8-dimethyl-4,7-di(phenylethynyl)-1,10-phenanthroline), was synthesized in seven total steps, prepared from either dichloro- or dibromophenanthroline precursors. Complete synthesis, structural characterization, and electrochemistry, in addition to static and dynamic photophysical properties of [Cu(sbmpep)2]+, are reported on all relevant time scales. UV-Vis absorption spectroscopy revealed significant increases in oscillator strength along with a concomitant bathochromic shift in the MLCT absorption bands with respect to structurally related model complexes (ε = 16 500 M-1 cm-1 at 491 nm)...
February 2, 2018: Inorganic Chemistry
Carolyn M Wilke, Bettina Wunderlich, Jean-François Gaillard, Kimberly A Gray
Due to their widespread use and subsequent release, engineered nanomaterials (ENMs) will create complex mixtures and emergent systems in the natural environment where their chemical interactions may cause toxic stress to microorganisms. We previously showed that under dark conditions n-TiO2 attenuated bacterial stress caused by low concentrations of n-Ag (<20 μg L-1) due to Ag+ adsorption. Yet, since both n-Ag and n-TiO2 are photoactive, their photochemistries may play a key role in their interactions. In this work, we study the chemical interactions of n-Ag and n-TiO2 mixtures in a natural aqueous medium under simulated solar irradiation to investigate the effects of photoinduced stress...
February 2, 2018: Environmental Science & Technology
Yingjie Li, Xiangliang Liu, Biaojun Zhang, Qun Zhao, Ping Ning, Senlin Tian
The ubiquity of sulfonamides (SAs) in natural waters requires insight into their environmental fate for ecological risk assessment. Extensive studies focused on the effect of univariate water constituents on the photochemical fate of SAs, yet the multivariate effects of water constituents in environmentally relevant concentrations on SA photodegradation are poorly understood. Here, response surface methodology was employed to explore the integrative effects of main water constituents (dissolved organic matter (DOM), NO3-, HCO3-, Cu2+) on the photodegradation of a representative SA (sulfamethazine)...
February 2, 2018: Environmental Science. Processes & Impacts
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