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Tommaso Michele Moles, Antonio Pompeiano, Thais Huarancca Reyes, Andrea Scartazza, Lorenzo Guglielminetti
Landraces represent an important part of the biodiversity well-adapted under limiting environmental conditions. We investigated the response of two Southern Italy tomato landraces, the well-known San Marzano (our commercial standard) and a local accession called "Ciettaicale", to different levels of sodium chloride in water irrigation (from 0 up to 600 mM) for a short-time exposure (one week). The combination of the chlorophyll a fluorescence and gas exchange analyses suggested that Ciettaicale maintained a higher efficiency of photosystem II (PSII) photochemistry and CO2 utilization at high salinity concentrations than San Marzano...
October 12, 2016: Plant Physiology and Biochemistry: PPB
Kyle D Custard, Kerri A Pratt, Siyuan Wang, Paul B Shepson
During springtime, unique halogen chemistry involving chlorine and bromine atoms controls the prevalence of volatile organic compounds, ozone, and mercury in the Arctic lower troposphere. In situ measurements of the chlorine monoxide radical (ClO) and its precursor Cl2, along with BrO and Br2, were conducted using chemical ionization mass spectrometry (CIMS) during the BRomine, Ozone, and Mercury EXperiment (BROMEX) near Barrow, Alaska in March 2012. To our knowledge, these data represent the first ClO measurements made using CIMS...
October 21, 2016: Environmental Science & Technology
James K Utterback, Amanda N Grennell, Molly B Wilker, Orion M Pearce, Joel D Eaves, Gordana Dukovic
In CdS nanocrystals, photoexcited holes rapidly become trapped at the particle surface. The dynamics of these trapped holes have profound consequences for the photophysics and photochemistry of these materials. Using a combination of transient absorption spectroscopy and theoretical modelling, we demonstrate that trapped holes in CdS nanorods are mobile and execute a random walk at room temperature. In CdS nanorods of non-uniform width, we observe the recombination of spatially separated electrons and trapped holes, which exhibits a t(-1/2) power-law decay at long times...
November 2016: Nature Chemistry
Anders Sandell, Davide Ragazzon, Andreas Schaefer, Mari Helene Farstad, Anne Borg
We present a dedicated synchrotron radiation photoelectron spectroscopy (SR-PES) study of a photochemical reaction on the surface of rutile TiO2(110). The photoreaction kinetics of carboxylate species (trimethyl acetate, TMA) upon irradiation by UV and soft x-rays were monitored and we show that it is possible to control the reaction rates from UV light and soft x-rays independently. We directly observe Ti4+ → Ti3+ conversion upon irradiation, attributed to electron trapping at Ti sites close to surface OH groups formed by deprotonation of the parent molecule, trimethyl acetic acid (TMAA)...
October 18, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Atanu Acharya, Alexey M Bogdanov, Bella L Grigorenko, Ksenia B Bravaya, Alexander V Nemukhin, Konstantin A Lukyanov, Anna I Krylov
Photoinduced reactions play an important role in the photocycle of fluorescent proteins from the green fluorescent protein (GFP) family. Among such processes are photoisomerization, photooxidation/photoreduction, breaking and making of covalent bonds, and excited-state proton transfer (ESPT). Many of these transformations are initiated by electron transfer (ET). The quantum yields of these processes vary significantly, from nearly 1 for ESPT to 10(-4)-10(-6) for ET. Importantly, even when quantum yields are relatively small, at the conditions of repeated illumination the overall effect is significant...
October 18, 2016: Chemical Reviews
L Tyler Mix, Julia Kirpich, Masato Kumauchi, Jie Ren, Mikas Vengris, Wouter D Hoff, Delmar S Larsen
We explored the photoisomerization mechanisms in novel homologs of Photoactive Yellow Protein (PYP) from Leptospira biflexa to identify conserved features and functional diversity in the primary photochemistry of this family of photoreceptors. In close agreement with the prototypical PYP from Halorhodospira halophila, we observe excited state absorbance near 375 nm and stimulated emission near 500 nm, with triphasic excited state decay. While the excited state decay for Lbif PYP is the slowest among known PYPs due to the redistribution of the amplitudes of the three decay components, the quantum yield for productive photocycle entry is very similar to that of Hhal PYP...
October 17, 2016: Biochemistry
Bradley W Abramson, Benjamin Kachel, David M Kramer, Daniel C Ducat
In plants, a limited capacity to utilize or export the end products of the Calvin Benson cycle (CB) from photosynthetically-active source cells to non-photosynthetic sink cells can result in reduced carbon capture, photosynthetic electron transport (PET) and lowered photochemical efficiency. The downregulation of photosynthesis caused by reduced capacity to utilize photosynthate has been termed "sink limitation". Recently, several cyanobacterial and algal strains engineered to over-produce target metabolites have exhibited increased photochemistry suggesting possible source-sink regulatory mechanisms may be involved...
October 13, 2016: Plant & Cell Physiology
Edoardo Torti, Stefano Protti, Daniele Merli, Daniele Dondi, Maurizio Fagnoni
The photochemical behavior of differently substituted N-arylsulfonimides was investigated. Homolysis of the S-N bond took place as the exclusive path from the singlet state to afford both N-arylsulfonamides and photo-Fries adducts, the amount of which depended on reaction conditions and aromatic substituents. Sulfinic and sulfonic acids were released upon irradiation under deaerated and oxygenated conditions, respectively. The nature of the excited states and intermediates involved were proved by laser flash photolysis and EPR experiments...
October 14, 2016: Chemistry: a European Journal
Fernando L Rosario-Ortiz, Silvio Canonica
The photochemical properties of dissolved organic matter (DOM) have been of interest to scientists and engineers since the 1970s. Upon light absorption, chromophoric DOM (CDOM) can sensitize the formation of different short-lived reactive intermediates (RIs), including hydroxyl radical ((•)OH), singlet oxygen ((1)O2) and superoxide radical anion (O2(-•)). In addition, a fraction of the excited singlet states in CDOM decays into excited triplet states ((3)CDOM*), which are also important photochemical transients in environmental systems...
October 13, 2016: Environmental Science & Technology
Mario Gutierrez, Boiko Cohen, Félix Sánchez, Abderrazzak Douhal
Understanding of the photocatalytic behaviour of Zr-based MOFs is fundamental for the improved design of new and more efficient photocatalysts. The present work describes steady-state and photodynamical studies on the behavior of two MOFs: Zr-2,6-naphthalene dicarboxylate (Zr-NDC) and Zr-4-amino-2,6-naphthalene dicarboxylate (Zr-NADC, 65% NDC/35% NADC) in dichloromethane (DCM) and N,N-dimethylformamide (DMF) suspensions. In the DMF suspension, the Zr-NDC MOF exhibits excimer formation in 280 ps due to the interactions between neighboring linkers...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Dariusz M Niedzwiedzki, Christopher Neil Hunter, Robert E Blankenship
Carotenoids are a class of natural pigments present in all phototrophic organisms, mainly in their light-harvesting proteins in which they play roles of accessory light absorbers and photoprotectors. Extensive time-resolved spectroscopic studies of these pigments have revealed unexpectedly complex photophysical properties, particularly for carotenoids in light-harvesting LH2 complexes from purple bacteria. An ambiguous, optically forbidden electronic excited state designated as S* has been postulated to be involved in carotenoid excitation relaxation and in an alternative carotenoid-to-bacteriochlorophyll energy transfer pathway, as well as being a precursor of the carotenoid triplet state...
October 11, 2016: Journal of Physical Chemistry. B
Karin Nienhaus, Gerd Ulrich Nienhaus
Photoactivatable fluorescent proteins (FPs) have become essential markers for nanoscopy on live specimens. In this issue of ACS Nano, Wang et al. present a reversibly photoswitching FP, GMars-Q, which they promote as an advanced marker for RESOLFT imaging because of its low residual intensity in the off state and low switching fatigue. Here, we explain the observed peculiar photobleaching behavior of GMars-Q by a mechanism that involves efficient shelving of proteins in dark states, resulting in low switching fatigue and low residual off intensity...
October 10, 2016: ACS Nano
Kristopher McNeill, Silvio Canonica
Excited triplet states of chromophoric dissolved organic matter ((3)CDOM*) play a major role among the reactive intermediates produced upon absorption of sunlight by surface waters. After more than two decades of research on the aquatic photochemistry of (3)CDOM*, the need for improving the knowledge about the photophysical and photochemical properties of these elusive reactive species remains considerable. This critical review examines the efforts to date to characterize (3)CDOM*. Information on (3)CDOM* relies mainly on the use of probe compounds because of the difficulties associated with directly observing (3)CDOM* using transient spectroscopic methods...
October 7, 2016: Environmental Science. Processes & Impacts
Rafał Szabla, Robert W Góra, Mikołaj Janicki, Jiří Šponer
Photochemically created πσ* states were classified among the most prominent factors determining the ultrafast radiationless deactivation and photostability of many biomolecular building blocks. In the past two decades, the gas phase photochemistry of πσ* excitations was extensively investigated and was attributed to N-H and O-H bond fission processes. However, complete understanding of the complex photorelaxation pathways of πσ* states in the aqueous environment was very challenging, owing to the direct participation of solvent molecules in the excited-state deactivation...
October 3, 2016: Faraday Discussions
Oleg Kostko, Tyler P Troy, Biswajit Bandyopadhyay, Musahid Ahmed
Proton transfer in aqueous media is a ubiquitous process, occurring in acid-base chemistry, biology, and in atmospheric photochemistry. Photoionization mass spectrometry coupled with theoretical calculations demonstrate that a relay-type proton transfer mechanism is operational for single-water-molecule-assisted proton transfer between two acetaldehyde molecules in the gas phase. Threshold photoionization of acetaldehyde-water clusters leads to proton transfer between the formyl groups (-CH[double bond, length as m-dash]O) of one acetaldehyde molecule to another, and the subsequent formation of cationic moieties...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Katharina Röttger, Hugo J B Marroux, Hendrik Böhnke, David T J Morris, Angus T Voice, Friedrich Temps, Gareth M Roberts, Andrew J Orr-Ewing
Ultrafast transient electronic and vibrational absorption spectroscopy (TEAS and TVAS) of 2'-deoxy-cytidine (dC) and 2'-deoxy-thymidine (dT) dissolved in chloroform examines their excited-state dynamics and the recovery of ground electronic state molecules following absorption of ultraviolet light. The chloroform serves as a weakly interacting solvent, allowing comparisons to be drawn with prior experimental studies of the photodynamics of these nucleosides in the gas phase and in polar solvents such as water...
September 16, 2016: Faraday Discussions
Kochise Bennett, Markus Kowalewski, Shaul Mukamel
Violations of the Born-Oppenheimer approximation (BOA) and the consequent nonadiabatic dynamics have long been an object of intense study. Recently, such dynamics have been induced via strong coupling of the molecule to a high-amplitude (spatially confined) mode of the electromagnetic field in optical cavities. However, the effects of a cavity on a pre-existing avoided crossing or conical intersection are relatively unexplored. The dynamics of molecules dressed by cavity modes are usually calculated by invoking the rotating wave approximation (RWA), which greatly simplifies the calculation but breaks down when the cavity mode frequency is higher than the relevant material frequencies...
September 29, 2016: Faraday Discussions
N D N Rodrigues, M Staniforth, J D Young, Y Peperstraete, N C Cole-Filipiak, J R Gord, P S Walsh, D M Hewett, T S Zwier, V G Stavros
Ultrafast time-resolved ion yield (TR-IY) and velocity map imaging spectroscopies are employed to reveal the relaxation dynamics after photoexcitation in ethyl 4-hydroxy-3-methoxycinnamate (ethyl ferulate, EF), an active ingredient in commercially available sunscreens. In keeping with a bottom-up strategy, the building blocks of EF, 2-methoxy-4-vinylphenol (MVP) and 4-hydroxy-3-methoxycinnamyl alcohol (coniferyl alcohol, ConA), were also studied to assist in our understanding of the dynamics of EF as we build up in molecular complexity...
September 16, 2016: Faraday Discussions
Lara Riehl, Alexander Seyboldt, Markus Ströbele, David Enseling, Thomas Jüstel, Michael Westberg, Peter R Ogilby, H-Jürgen Meyer
Octahedral tungsten iodide clusters equipped with apical ligands (L) are synthesized to implement substantial photophysical properties. The [W6I8(CF3COO)6](2-) cluster reported herein is the first example of a family of ligand substituted [W6I8L6](2-) clusters. Such compounds are expected to exhibit a rich photochemistry in which the apical ligands play a crucial role. The versatile solid state and solution phase photophysical properties of (TBA)2[W6I8(CF3COO)6] described herein parallel characteristics obtained in some photophysically active organic compounds, including a broad absorption in the UV/VIS region...
October 4, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Yoann Peperstraete, Michael Staniforth, Lewis A Baker, Natércia D N Rodrigues, Neil C Cole-Filipiak, Wen-Dong Quan, Vasilios G Stavros
Methyl-E-4-methoxycinnamate (E-MMC) is a model chromophore of the commonly used commercial sunscreen agent, 2-ethylhexyl-E-4-methoxycinnamate (E-EHMC). In an effort to garner a molecular-level understanding of the photoprotection mechanisms in operation with E-EHMC, we have used time-resolved pump-probe spectroscopy to explore E-MMC's and E-EHMC's excited state dynamics upon UV-B photoexcitation to the S1 (1(1)ππ*) state in both the gas- and solution-phase. In the gas-phase, our studies suggest that the excited state dynamics are driven by non-radiative decay from the 1(1)ππ* to the S3 (1(1)nπ*) state, followed by de-excitation from the 1(1)nπ* to the ground electronic state (S0)...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
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