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https://www.readbyqxmd.com/read/28206747/ultrafast-dynamics-of-manganese-iii-manganese-ii-and-free-base-bacteriochlorin-is-there-time-for-photochemistry
#1
Fabio A Schaberle, Artur R Abreu, Nuno P F Gonçalves, Gonçalo F F Sá, Mariette M Pereira, Luís G Arnaut
Manganese(III) and manganese(II) complexes of halogenated sulfonamide tetraphenylbacteriochlorins were prepared for the first time via a transmetalation reaction and shown to be stable at room temperature. The behavior of the electronic states of the paramagnetic complexes is remarkably different from those of the metal-free bacteriochlorins or diamagnetic metallobacteriochlorins. The Mn(3+) complex exhibits eight electronic transitions between different states from 300 to 1100 nm, with a very prominent band (molar absorption coefficient of ca...
February 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28199904/cyclic-electron-flow-may-provide-some-protection-against-psii-photoinhibition-in-rice-oryza-sativa-l-leaves-under-heat-stress
#2
Jemaa Essemine, Yi Xiao, Mingnan Qu, Hualing Mi, Xin-Guang Zhu
Previously we have shown that a quick down-regulation in PSI activity compares to that of PSII following short-term heat stress for two rice groups including C4023 and Q4149, studied herein. These accessions were identified to have different natural capacities in driving cyclic electron flow (CEF) around PSI; i.e., low CEF (lcef) and high CEF (hcef) for C4023 and Q4149, respectively. The aim of this study was to investigate whether these two lines have different mechanisms of protecting photosystem II from photodamage under heat stress...
January 30, 2017: Journal of Plant Physiology
https://www.readbyqxmd.com/read/28199106/mechanistic-studies-of-the-photoinduced-quinone-trimethyl-lock-decaging-process
#3
Clinton J Regan, David P Walton, Oliver S Shafaat, Dennis A Dougherty
Mechanistic studies of a general reaction that decages a wide range of substrates on exposure to visible light are described. The reaction involves a photochemically initiated reduction of a quinone mediated by an appended thioether. After reduction, a trimethyl lock system incorporated into the quinone leads to decaging. The reaction could be viewed as an electron-transfer initiated reduction of the quinone or as a hydrogen abstraction - Norrish Type II - reaction. Product analysis, kinetic isotope effects, stereochemical labeling, radical clock, and transient absorption studies support the electron transfer mechanism...
February 15, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28198051/energy-vs-electron-transfer-controlling-the-excitation-transfer-in-molecular-triads
#4
Yusen Luo, Kevin Barthelmes, Maria Wächtler, Andreas Winter, Ulrich S Schubert, Benjamin Dietzek
The photochemistry of Ru(II) coordination compounds is generally discussed to originate from the lowest lying triplet metal-to-ligand charge-transfer state (3MLCT). However, when heteroleptic complexes are considered, e.g. in the design of molecular triads for efficient photoinduced charge separation, a complex structure of 1MLCT states, which can be populated in a rather narrow spectral window (typically around 450 nm) is to be considered. In this communication we show that the localization of MLCT excited states on different ligands can affect the following ps to ns decay pathways to an extend that by tuning the excitation wavelength intermolecular energy transfer from a Ru(II)-terpyridine unit to a fullerene acceptor can be favored over electron transfer within the molecular triad...
February 15, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28195487/sequential-proton-coupled-electron-transfer-mediates-excited-state-deactivation-of-a-eumelanin-building-block
#5
Juan J Nogueira, Alice Corani, Amal El Nahhas, Alessandro Pezzella, Marco d'Ischia, Leticia Gonzalez, Villy Sundstrom
Skin photoprotection is commonly believed to rely on the photochemistry of 5,6-dihydroxyindole (DHI)- and 5,6-dihydroxyindole-2-carboxylic acid (DHICA)-based eumelanin building blocks. Attempts to elucidate the underlying excited-state relaxation mechanisms have been partly unsuccessful due to the marked instability to oxidation. Herein, we report a study of the excited-state deactivation of DHI using steady-state and time-resolved fluorescence accompanied by high-level quantum chemistry calculations including solvent effects...
February 14, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28186003/imaging-the-photoinduced-charge-injection-in-cds-tio2-nanoparticles-by-the-sequential-fluorescence-mapping-method
#6
Rafael Frederice, Diego Lencione, Marcelo H Gehlen
The combination of a sensitizer and TiO2 nanoparticles forming a photocatalytic material is a central issue in many fields of applied photochemistry. The charge injection of emissive sensitizers into the conduction band of the semiconductor TiO2 may form a photoactive region that becomes dark, or it has a very low emission signal due to the generation of sensitizer radicals. However, by sequential coupling of a selected photoredox dye, such as resazurin, the dark region may become fluorescent at the interfaces where the charge injection has taken place due to the concomitant formation of fluorescent resorufin by cascade electron transfer...
February 10, 2017: Methods and Applications in Fluorescence
https://www.readbyqxmd.com/read/28185001/arbuscular-mycorrhizas-influence-lycium-barbarum-tolerance-of-water-stress-in-a-hot-environment
#7
Wentao Hu, Haoqiang Zhang, Hui Chen, Ming Tang
Arbuscular mycorrhizal (AM) fungi can assist their hosts to cope with water stress and other abiotic stresses in different ways. In order to test whether AM plants have a greater capacity than control plants to cope with water stress, we investigated the water status and photosynthetic capacity of Lycium barbarum colonized or not by the AM fungus Rhizophagus irregularis under three water conditions during a hot summer. Sugar levels and transcriptional responses of both plant and AM fungus aquaporin genes in roots were analyzed...
February 9, 2017: Mycorrhiza
https://www.readbyqxmd.com/read/28182184/surface-plasmon-polariton-induced-hot-carrier-generation-for-photocatalysis
#8
Wonmi Ahn, Daniel C Ratchford, Pehr E Pehrsson, Blake S Simpkins
Non-radiative plasmon decay in noble metals generates highly energetic carriers under visible light irradiation, which opens new prospects in the fields of photocatalysis, photovoltaics, and photodetection. While localized surface plasmon-induced hot carrier generation occurs in diverse metal nanostructures, inhomogeneities typical of many metal-semiconductor plasmonic nanostructures hinder predictable control of photocarrier generation and therefore reproducible carrier-mediated photochemistry. Here, we generate traveling surface plasmon polaritons (SPPs) at the interface between a noble metal/titanium dioxide (TiO2) heterostructure film and aqueous solution, enabling simultaneous optical and electrochemical interrogation of plasmon-mediated chemistry in a system whose resonance may be continuously tuned via the incident optical excitation angle...
February 9, 2017: Nanoscale
https://www.readbyqxmd.com/read/28177626/surface-ligand-mediated-plasmon-driven-photochemical-reactions
#9
Bijesh Kafle, Marisa Poveda, Terefe G Habteyes
Contrary to the general expectation that surface ligands reduce the reactivity of surfaces by blocking the active sites, we present experimental evidence that surface ligands can in fact increase reactivity and induce important reaction pathways in plasmon-driven surface photochemistry. The remarkable effect of surface ligands is demonstrated by comparing the photochemistry of p-aminothiophenol (PATP) on resonant plasmonic gold nanorods (AuNRs) in the presence of citrate, hexadecyltrimethylammonium bromide (CTAB), and no surface ligands under visible light irradiation...
February 8, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28175984/three-bilindione-isomers-synthesis-characterization-and-reactivity-of-biliverdin-analogs
#10
Jun-Fei Wang, Fang Ma, Hao-Ling Sun, Jing Zhang, Jun-Long Zhang
Linear tetrapyrrole is the core structure of light-sensitive native cofactors such as phycocyanobilin, phytochromobilin and bile pigments, which attracts increasing attention in biomimetic chemistry, photochemistry and coordination chemistry. To decipher the relationship between structures and functions, in this work, we firstly reported the synthesis, isolation and characterization of three bilindione isomers (ZZZ, syn, syn, syn 1, EZE, syn, syn, anti 2 and EZE, anti, syn, anti 3) bearing meso-pentafluorophenyl groups...
February 7, 2017: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/28170268/disclosing-whole-reaction-pathways-of-photochromic-3h-naphthopyrans-with-fast-color-fading
#11
Sabina Brazevic, Michel Sliwa, Yoichi Kobayashi, Jiro Abe, Gotard Burdzinski
Instantaneous coloration with large absorbance and quick color fading in the dark are desired properties for thermally reversible photochromic compounds. In the case of naphthopyran derivatives, which have been employed to commercial ophthalmic lenses, the quick color fading has been recently achieved by suppression of the generation of the transoid-trans (TT) form by steric hindrance of bulky substituents. However, there are still open questions whether the steric hindrance decreases the photochromic reaction efficiency, which is a crucial problem for industrial applications...
February 9, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28169548/surface-ligand-mediated-plasmon-driven-photochemical-reactions
#12
Bijesh Kafle, Marisa Poveda, Terefe G Habteyes
Contrary to the general expectation that surface ligands reduce the reactivity of surfaces by blocking the active sites, we present experimental evidence that surface ligands can in fact increase reactivity and induce important reaction pathways in plasmon-driven surface photochemistry. The remarkable effect of surface ligands is demonstrated by comparing the photochemistry of p-aminothiophenol (PATP) on resonant plasmonic gold nanorods (AuNRs) in the presence of citrate, hexadecyltrimethylammonium bromide (CTAB), and no surface ligands under visible light irradiation...
February 7, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28153404/surface-ozone-characterization-at-larsemann-hills-and-maitri-antarctica
#13
Kaushar Ali, D K Trivedi, S K Sahu
Data are analyzed in terms of daily average ozone, its diurnal variation and its relation with meteorological parameters like dry bulb temperature (T), wet bulb temperature (Tw), atmospheric pressure and wind speed based on measurement of these parameters at two Indian Antarctic stations (Larsemann Hills, and Maitri) during 28th Indian Scientific Expedition of Antarctica (ISEA) organized during Antarctic summer of the year 2008-09. The work has been carried out to investigate summer time ozone level and its day-to-day and diurnal variability at these coastal locations and to highlight possible mechanism of ozone production and destruction...
January 30, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28142311/molecular-photofragmentation-dynamics-in-the-gas-and-condensed-phases
#14
Michael N R Ashfold, Daniel Murdock, Thomas A A Oliver
Exciting a molecule with an ultraviolet photon often leads to bond fission, but the final outcome of the bond cleavage is typically both molecule and phase dependent. The photodissociation of an isolated gas-phase molecule can be viewed as a closed system: Energy and momentum are conserved, and the fragmentation is irreversible. The same is not true in a solutionphase photodissociation process. Solvent interactions may dissipate some of the photoexcitation energy prior to bond fission and will dissipate any excess energy partitioned into the dissociation products...
January 30, 2017: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/28135083/polarized-xanes-monitors-femtosecond-structural-evolution-of-photoexcited-vitamin-b12
#15
Nicholas A Miller, Aniruddha Deb, Roberto Alonso-Mori, Brady D Garabato, James M Glownia, Laura M Kiefer, Jake Koralek, Marcin Sikorski, Kenneth G Spears, Theodore E Wiley, Diling Zhu, Pawel M Kozlowski, Kevin J Kubarych, James E Penner-Hahn, Roseanne J Sension
Ultrafast, polarization-selective time-resolved X-ray absorption near-edge structure (XANES) was used to characterize the photochemistry of vitamin B12, cyanocobalamin (CNCbl), in solution. Cobalamins are important biological cofactors involved in methyl transfer, radical rearrangement, and light-activated gene regulation, while also holding promise as light-activated agents for spatiotemporal controlled delivery of therapeutics. We introduce polarized femtosecond XANES, combined with UV-visible spectroscopy, to reveal sequential structural evolution of CNCbl in the excited electronic state...
January 30, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28133433/bioconjugatable-pegylated-hydroporphyrins-for-photochemistry-and-photomedicine-narrow-band-near-infrared-emitting-bacteriochlorins
#16
Nuonuo Zhang, Jianbing Jiang, Mengran Liu, Masahiko Taniguchi, Amit Kumar Mandal, Rosemary B Evans-Storms, J Bruce Pitner, David F Bocian, Dewey Holten, Jonathan S Lindsey
Synthetic bacteriochlorins absorb in the near-infrared (NIR) region and are versatile analogues of natural bacteriochlorophylls. The utilization of these chromophores in energy sciences and photomedicine requires the ability to tailor their physicochemical properties, including the incorporation of units to impart water solubility. Herein, we report the synthesis, from two common bacteriochlorin building blocks, of five wavelength-tunable, bioconjugatable and water-soluble bacteriochlorins along with two non-bioconjugatable benchmarks...
September 1, 2016: New Journal of Chemistry, Nouveau Journal de Chimie
https://www.readbyqxmd.com/read/28129341/photoinactivation-of-photosystem-ii-in-prochlorococcus-and-synechococcus
#17
Cole D Murphy, Mitchell S Roodvoets, Emily J Austen, Allison Dolan, Audrey Barnett, Douglas A Campbell
The marine picocyanobacteria Synechococcus and Prochlorococcus numerically dominate open ocean phytoplankton. Although evolutionarily related they are ecologically distinct, with different strategies to harvest, manage and exploit light. We grew representative strains of Synechococcus and Prochlorococcus and tracked their susceptibility to photoinactivation of Photosystem II under a range of light levels. As expected blue light provoked more rapid photoinactivation than did an equivalent level of red light...
2017: PloS One
https://www.readbyqxmd.com/read/28128377/recent-developments-in-reversible-photoregulation-of-oligonucleotide-structure-and-function
#18
REVIEW
Anouk S Lubbe, Wiktor Szymanski, Ben L Feringa
There is a growing interest in the photoregulation of biological functions, due to the high level of spatiotemporal precision achievable with light. Additionally, light is non-invasive and waste-free. In particular, the photoregulation of oligonucleotide structure and function is a rapidly developing study field with relevance to biological, physical and material sciences. Molecular photoswitches have been incorporated in oligonucleotides for 20 years, and the field has currently grown beyond fundamental studies on photochemistry of the switches and DNA duplex stability, and is moving towards applications in chemical biology, nanotechnology and material science...
January 27, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/28126814/photosensitized-energy-transfer-mediated-organometallic-catalysis-through-electronically-excited-nickel-ii
#19
Eric R Welin, Chip Le, Daniela M Arias-Rotondo, James K McCusker, David W C MacMillan
Transition metal catalysis has traditionally relied on organometallic complexes that can cycle through a series of ground-state oxidation levels to achieve a series of discrete yet fundamental fragment-coupling steps. The viability of excited-state organometallic catalysis via direct photoexcitation has been demonstrated. Although the utility of triplet sensitization by energy transfer has long been known as a powerful activation mode in organic photochemistry, it is surprising to recognize that photosensitization mechanisms to access excited-state organometallic catalysts have lagged far behind...
January 27, 2017: Science
https://www.readbyqxmd.com/read/28121132/molecular-composition-and-photochemical-reactivity-of-size-fractionated-dissolved-organic-matter
#20
Andrew Chapin Maizel, Christina K Remucal
The photochemical production of reactive species, such as triplet dissolved organic matter ((3)DOM) and singlet oxygen ((1)O2), contributes to the degradation of aquatic contaminants and is related to an array of DOM structural characteristics, notably molecular weight. In order to relate DOM molecular weight, optical properties, and reactive species production, Suwannee River (SRFA) and Pony Lake fulvic acid (PLFA) isolates are fractionated by sequential ultrafiltration and the resultant fractions are evaluated in terms of molecular composition and photochemical reactivity...
January 25, 2017: Environmental Science & Technology
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