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https://www.readbyqxmd.com/read/28644828/a-mutant-of-chlamydomonas-without-lhcsr-maintains-high-rates-of-photosynthesis-but-has-reduced-cell-division-rates-in-sinusoidal-light-conditions
#1
Michael Cantrell, Graham Peers
The LHCSR protein belongs to the light harvesting complex family of pigment-binding proteins found in oxygenic photoautotrophs. Previous studies have shown that this complex is required for the rapid induction and relaxation of excess light energy dissipation in a wide range of eukaryotic algae and moss. The ability of cells to rapidly regulate light harvesting between this dissipation state and one favoring photochemistry is believed to be important for reducing oxidative stress and maintaining high photosynthetic efficiency in a rapidly changing light environment...
2017: PloS One
https://www.readbyqxmd.com/read/28640617/5-methylhydantoin-from-isolated-molecules-in-a-low-temperature-argon-matrix-to-solid-state-polymorphs-characterization
#2
Bernardo A Nogueira, Gulce O Ildiz, João Canotilho, M Ermelinda S Eusébio, Marta Sofia C Henriques, José A Paixão, Rui Fausto
The molecular structure, vibrational spectra and photochemistry of 5-methylhydantoin (C4H6N2O2; 5-MH) were studied by matrix isolation infrared spectroscopy and theoretical calculations at the DFT(B3LYP)/6-311++G(d,p) theory level. The Natural Bond Orbital (NBO) analysis approach was used to study in detail the electronic structure of the minimum energy structure of 5-MH, namely the specific characteristics of the σ and π electronic systems of the molecule, and the stabilizing orbital interactions. UV irradiation of 5-MH isolated in argon matrix resulted in its photofragmentation through a single photochemical pathway, yielding isocyanic acid, ethanimine and carbon monoxide, thus following a pattern already observed before for the parent hydantoin and 1-methylhydantoin molecules...
June 22, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28637094/acclimation-responses-to-high-light-by-guazuma-ulmifolia-lam-malvaceae-leaves-at-different-stages-of-development
#3
Anderson Kikuchi Calzavara, Juliana Silva Rocha, Geovana Lourenço, Karina Sanada, Cristiano Medri, Edmilson Bianchini, José Antonio Pimenta, Renata Stolf-Moreira, Halley Caixeta Oliveira
The recomposition of deforested environments requires the prior acclimation of seedlings to full sun in nurseries. Seedlings can overcome excessive light either through the acclimation of pre-existing fully expanded leaves or through the development of new leaves that are acclimated to the new light environment. Here, we compared the acclimation capacity of mature (MatL, fully expanded at the time of transfer) and newly expanded leaves (NewL, expanded after the light shift) of Guazuma ulmifolia Lam. (Malvaceae) seedlings to high light...
June 21, 2017: Plant Biology
https://www.readbyqxmd.com/read/28632317/qm-mm-study-on-the-photoreactions-of-dark-and-light-adapted-states-of-a-blue-light-ytva-lov-photoreceptor
#4
Xue-Ping Chang, Yuan-Jun Gao, Wei-Hai Fang, Ganglong Cui, Walter Thiel
The dark- and light-adapted states of YtvA LOV domains exhibit distinct excited-state behavior. We have employed high-level QM(MS-CASPT2)/MM calculations to study the photochemical reactions of the dark- and light-adapted states. The photoreaction from the dark-adapted state starts with an S1→T1 intersystem crossing followed by a triplet-state hydrogen transfer from the thiol to the flavin moiety that produces a diradical intermediate, and a subsequent internal conversion that triggers a barrierless C-S bond formation in the S0 state...
June 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28631486/melding-caged-compounds-with-supramolecular-containers-photogeneration-and-miscreant-behavior-of-the-coumarylmethyl-carbocation
#5
Nareshbabu Kamatham, José P Da Silva, Richard S Givens, V Ramamurthy
By merging well-established concepts of supramolecular chemistry, protecting group strategy, and photochemistry, we have solubilized in water hydrophobic organic molecules consisting of a photoactive protecting group and masked carboxylic acids, released the desired acid, and confined a reactive carbocation intermediate within a capsule. Confinement of the photogenerated carbocation brought out the latent radical-like behavior. This observation is consistent with the recent theoretical prediction of the 7-(diethylamino)coumarinyl-4-methyl carbocation having a triplet diradical ground-state electronic contribution...
June 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28626565/site-specific-azide-acetyllysine-photochemistry-on-epigenetic-readers-for-interactome-profiling
#6
Babu Sudhamalla, Debasis Dey, Megan Breski, Tiffany Nguyen, Kabirul Islam
Chemical modifications on DNA, RNA and histones are recognized by an array of 'reader' modules to regulate transcriptional programming and cell fate. However, identification of reader-specific interacting partners in a dynamic cellular environment remains a significant challenge. Herein, we report a chemoproteomic approach termed 'interaction-based protein profiling' (IBPP) to characterize novel interacting partners of potentially any reader protein. IBPP harnesses a photosensitive amino acid introduced into the hydrophobic pocket of a reader module to crosslink and enrich transient interacting partners that are inaccessible to traditional methods...
June 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28620938/anisotropic-metal-deposition-on-tio2-particles-by-electric-field-induced-charge-separation
#7
Supakit Tiewcharoen, Chompunuch Warakulwit, Veronique Lapeyre, Patrick Garrigue, Lucas Fourier, Catherine Ellisalde, Sonia Buffière, Philippe Legros, Marion Gayot, Jumras Limtrakul, Alexander Kuhn
Deposition of metals on TiO2 semiconductor particles (M-TiO2) results in hybrid Janus objects combining the interesting properties of both materials. One of the techniques that have been proposed to generate Janus particles is bipolar electrochemistry (BPE). The concept can be applied in a straightforward way for the site selective modification of conducting particles, but is less obvious to use for semiconductors. In this work we report the bulk synthesis of anisotropic M-TiO2 particles based on the synergy of BPE and photochemistry, allowing to overcome intrinsic limitations when they are used separately...
June 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28618782/ab-initio-nonadiabatic-dynamics-with-coupled-trajectories-a-rigorous-approach-to-quantum-de-coherence
#8
Seung Kyu Min, Federica Agostini, Ivano Tavernelli, E K U Gross
We report the first nonadiabatic molecular dynamics study based on the exact factorization of the electron-nuclear wave function. Our approach (a coupled-trajectory mixed quantum-classical, CT-MQC, scheme) is based on the quantum-classical limit derived from systematic and controlled approximations to the full quantum-mechanical problem formulated in the exact-factorization framework. Its strength is the ability to correctly capture quantum (de)coherence effects in a trajectory-based approach to excited-state dynamics...
June 19, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28617585/solution-phase-photochemical-nanopatterning-enabled-by-high-refractive-index-beam-pen-arrays
#9
Zhuang Xie, Pavlo Gordiichuk, Qing-Yuan Lin, Brian Meckes, Peng-Cheng Chen, Lin Sun, Jingshan S Du, Jinghan Zhu, Yuan Liu, Vinayak P Dravid, Chad A Mirkin
A high-throughput, solution-based, scanning-probe photochemical nanopatterning approach, which does not require the use of probes with subwavelength apertures, is reported. Specifically, pyramid arrays made from high-refractive-index polymeric materials were constructed and studied as patterning tools in a conventional liquid-phase beam pen lithography experiment. Two versions of the arrays were explored with either metal-coated or metal-free tips. Importantly, light can be channeled through both types of tips and the appropriate solution phase (e...
June 15, 2017: ACS Nano
https://www.readbyqxmd.com/read/28613070/engineering-high-potential-photo-oxidants-with-panchromatic-absorption
#10
Ting Jiang, Nicholas F Polizzi, Jeff Rawson, Michael J Therien
Challenging photochemistry demands high-potential visible-light-absorbing photo-oxidants. We report (i) a highly electron-deficient Ru(II) complex (eDef-Rutpy) bearing an E1/2(0/+) potential more than 300 mV more positive than that of any established Ru(II) bis(terpyridyl) derivative, and (ii) an ethyne-bridged eDef-Rutpy-(porphinato)Zn(II) (eDef-RuPZn) supermolecule that affords both panchromatic UV-vis spectral domain absorptivity and a high E1/2(0/+) potential, comparable to that of Ce(NH4)2(NO3)6 [E1/2(Ce(3+/4+)) = 1...
June 14, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28609735/typical-winter-haze-pollution-in-zibo-an-industrial-city-in-china-characteristics-secondary-formation-and-regional-contribution
#11
Hui Li, Yongliang Ma, Fengkui Duan, Kebin He, Lidan Zhu, Tao Huang, Takashi Kimoto, Xiaoxuan Ma, Tao Ma, Lili Xu, Beiyao Xu, Shuo Yang, Siqi Ye, Zhenli Sun, Jiutao An, Zhaolu Zhang
Heavy haze pollution occurs frequently in northern China, most critically in the Beijing-Tianjin-Hebei area (BTH). Zibo, an industrial city located in Shandong province, is often listed as one of the top ten most polluted cities in China, particularly in winter. However, no studies of haze in Zibo have been conducted, which limits the understanding of the source and formation of haze pollution in this area, as well as mutual effects with the BTH area. We carried out online and continuous integrated field observation of particulate matter in winter, from 11 to 25 January 2015...
June 10, 2017: Environmental Pollution
https://www.readbyqxmd.com/read/28607440/an-arabidopsis-mutant-with-high-operating-efficiency-of-photosystem-ii-and-low-chlorophyll-fluorescence
#12
Niels van Tol, Martijn Rolloos, Dieuwertje Augustijn, A Alia, Huub J de Groot, Paul J J Hooykaas, Bert J van der Zaal
The overall light energy to biomass conversion efficiency of plant photosynthesis is generally regarded as low. Forward genetic screens in Arabidopsis have yielded very few mutants with substantially enhanced photochemistry. Here, we report the isolation of a novel Arabidopsis mutant with a high operating efficiency of Photosystem II (φPSII) and low chlorophyll fluorescence from a library of lines harboring T-DNA constructs encoding artificial transcription factors. This mutant was named Low Chlorophyll Fluorescence 1 (LCF1)...
June 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28605184/modeling-photosensitized-secondary-organic-aerosol-formation-in-laboratory-and-ambient-aerosols
#13
William G Tsui, Yi Rao, Hai-Lung Dai, V Faye McNeill
Photosensitized reactions involving imidazole-2-carboxaldehyde (IC) have been experimentally observed to contribute to secondary organic aerosol (SOA) growth. However, the extent of photosensitized reactions in ambient aerosols remains poorly understood and unaccounted for in atmospheric models. Here we use GAMMA 4.0, a photochemical box model that couples gas-phase and aqueous-phase aerosol chemistry, along with recent laboratory measurements of the kinetics of IC photochemistry, to analyze IC-photosensitized SOA formation in laboratory and ambient settings...
June 22, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28603957/the-impact-of-nanomorphology-on-the-photochemistry-of-fullerene-films-correlating-stability-to-triplet-exciton-kinetics
#14
Emily M Speller, James D McGettrick, Beth Rice, Andrew M Telford, Harrison K H Lee, Ching-Hong Tan, Catherine S De Castro, Matthew Lloyd Davies, Trystan M Watson, Jenny Nelson, James R Durrant, Zhe Li, Wing Chung Tsoi
The photochemistry and stability of fullerene films is found to be strongly dependent upon film nanomorphology. In particular, PC61BM blend films, dispersed with polystyrene, are found to be more susceptible to photobleaching in air than the more aggregated neat films. This enhanced photobleaching correlated with increased oxygen quenching of PC61BM triplet states, and the appearance of a carbonyl FTIR absorption band indicative of fullerene oxidation. sug-gesting PC61BM photo-oxidation is primarily due to triplet-mediated singlet oxygen generation...
June 12, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28601032/photoinduced-transformation-of-pyridinium-based-ionic-liquids-and-implications-for-their-photochemical-behavior-in-surface-waters
#15
Paola Calza, Giorgio Noè, Debora Fabbri, Valentina Santoro, Claudio Minero, Davide Vione, Claudio Medana
The photochemical reactivity of three ionic liquids (1-ethylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium tetrafluoroborate, and 1-(3-cyanopropyl)pyridinium chloride) was studied by combining laboratory experiments and photochemical modeling, to get insight into the possible behavior in surface-water environments. Among the studied compounds, phototransformation in sunlit surface waters could be an important attenuation pathway for 1-butyl-4-methylpyridinium tetrafluoroborate (BMPOTFB). In this case the reaction with the carbonate radicals (CO3(-)) would prevail at low values of the dissolved organic carbon (DOC), while the direct photolysis would be important at intermediate to high DOC values...
May 30, 2017: Water Research
https://www.readbyqxmd.com/read/28598469/interfacial-photochemistry-of-biogenic-surfactants-a-major-source-of-abiotic-volatile-organic-compounds
#16
Martin Brüggemann, Nathalie Hayeck, Chloé Bonnineau, Stéphane Pesce, Peter A Alpert, Sébastien Perrier, Christoph Zuth, Thorsten Hoffmann, Jianmin Chen, Christian George
Films of biogenic compounds exposed to the atmosphere are ubiquitously found on the surfaces of cloud droplets, aerosol particles, buildings, plants, soils and the ocean. These air/water interfaces host countless amphiphilic compounds concentrated there with respect to in bulk water, leading to a unique chemical environment. Here, photochemical processes at the air/water interface of biofilm-containing solutions were studied, demonstrating abiotic VOC production from authentic biogenic surfactants under ambient conditions...
June 9, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28597431/antioxidant-responses-and-photosynthetic-behaviors-of-kappaphycus-alvarezii-and-kappaphycus-striatum-rhodophyta-solieriaceae-during-low-temperature-stress
#17
Hu Li, Jianguo Liu, Litao Zhang, Tong Pang
BACKGROUND: Kappaphycus are farmed in tropical countries as raw material for carrageenan, which is widely used in food industry. The sea area available for farming is one limiting factor in the production of seaweeds. Though cultivation is spreading into subtropical regions, the lower seawater temperature is an important problem encountered in subtropical regions for the farming of Kappaphycus. This research of physiological response to low temperature stress will be helpful for screening Kappaphycus strains for growth in a lower temperature environment...
December 2016: Botanical Studies (Taipei, Taiwan)
https://www.readbyqxmd.com/read/28595406/an-alternative-laser-driven-photodissociation-mechanism-of-pyrrole-via-%C3%AF-%C3%AF-1%C3%A2-s0-conical-intersection
#18
K R Nandipati, Z Lan, H Singh, S Mahapatra
A first principles quantum dynamics study of N-H photodissociation of pyrrole on the S0-(1)πσ(*)(A21) coupled electronic states is carried out with the aid of an optimally designed UV-laser pulse. A new photodissociation path, as compared to the conventional barrier crossing on the πσ*1 state, opens up upon electronic transitions under the influence of pump-dump laser pulses, which efficiently populate both the dissociation channels. The interplay of electronic transitions due both to vibronic coupling and the laser pulse is observed in the control mechanism and discussed in detail...
June 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28593746/long-term-measurements-of-chlorophyll-a-fluorescence-using-the-jip-test-show-that-combined-abiotic-stresses-influence-the-photosynthetic-performance-of-the-perennial-ryegrass-lolium-perenne-in-a-managed-temperate-grassland
#19
Anthony Digrado, Aurélie Bachy, Ahsan Mozaffar, Niels Schoon, Filippo Bussotti, Crist Amelynck, Anne-Catherine Dalcq, Marie-Laure Fauconnier, Marc Aubinet, Bernard Heinesch, Patrick du Jardin, Pierre Delaplace
Several experiments have highlighted the complexity of stress interactions involved in plant response. The impact in field conditions of combined environmental constraints on the mechanisms involved in plant photosynthetic response, however, remains understudied. In a long-term field study performed in a managed grassland, we investigated the photosynthetic apparatus response of the perennial ryegrass (Lolium perenne) to environmental constraints and its ability to recover and acclimatize. Frequent field measurements of chlorophyll ɑ fluorescence (ChlF) were made in order to determine the photosynthetic performance response of a population of L...
June 8, 2017: Physiologia Plantarum
https://www.readbyqxmd.com/read/28592110/mechanism-of-photocatalytic-water-splitting-with-graphitic-carbon-nitride-photochemistry-of-the-heptazine-water-complex
#20
Johannes Ehrmaier, Tolga N V Karsili, Andrzej L Sobolewski, Wolfgang Domcke
Impressive progress has recently been achieved in photocatalytic hydrogen evolution with polymeric carbon nitride materials consisting of heptazine building blocks. However, the fundamental mechanistic principles of the catalytic cycle are as yet poorly understood. Here, we provide first-principles computational evidence that water splitting with heptazine-based materials can be understood as a molecular excited-state reaction taking place in hydrogen-bonded heptazine-water complexes. The oxidation of water occurs homolytically via an electron/proton transfer from water to heptazine, resulting in ground-state heptazinyl and OH radicals...
June 16, 2017: Journal of Physical Chemistry. A
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