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Photochemical & Photobiological Sciences

Anabel E Lanterna, María González-Béjar, Mathieu Frenette, Juan C Scaiano
The photophysical behaviour of 7-mercapto-4-methylcoumarin (C-SH) and derivatives has been studied in different solvents. In contrast to 7-hydroxy-4-methylcoumarin, C-SH shows poor emission, but high fluorescence when the thiol is alkylated. The origin and character of the lowest singlet states are discussed, specifically proposing that the thione-like C[double bond, length as m-dash]S resonance form plays a key role in excited state deactivation in C-SH.
June 26, 2017: Photochemical & Photobiological Sciences
Jianlei Han, Fei Zhang, Jing You, Yonemura Hiroaki, Sunao Yamada, Toru Morifuji, Shirong Wang, Xianggao Li
Metallophthalocyanines (MPc-o-Cou, M = Fe, Co, Ni, and Cu) with fourth period metal ions have been successfully applied as a sensitizer coupled with rubrene (Rub) in photon upconversion based on triplet-triplet annihilation. An upconversion quantum yield (ϕPUC) of up to 4.82% was observed in the CoPc-o-Cou : Rub couple. The absorption and phosphorescence emission spectra showed that the Q bands and phosphorescence emission peaks were dramatically dependent on the number of d-electrons of the metal ions in MPc-o-Cou...
June 26, 2017: Photochemical & Photobiological Sciences
Lara Martínez-Fernández, Roberto Improta
Despite the biological relevance of AT-rich DNA sequences, the excited state paths associated with the photochemical reactions involving adenine and thymine stacked pairs have never been characterized, and the structure of the most abundant photoproduct in DNA is unknown. PCM/TD-M052X calculations on dApT and TpdA unveil the paths leading to the main photoproduct in TpdA, provide new insights into the reasons why it is not formed in dApT and show the existence of a new photochemical path, which could produce the precursor of the most abundant genomic AT/TA photoproduct...
June 22, 2017: Photochemical & Photobiological Sciences
Christian Espinosa-Bustos, Diego Cortés-Arriagada, Marco A Soto-Arriaza, José Robinson-Duggon, Nancy Pizarro, Alan R Cabrera, Denis Fuentealba, Cristian O Salas
In this paper, we explored the fluorescence properties of eight aurone derivatives bearing methoxy groups and bromine atoms as substituents in the benzene rings. All derivatives showed strong solvatochromic absorption and emission properties in solvents of different polarities. Some of them showed high fluorescence quantum yields, which make them potential compounds for sensing applications. The position of the methoxy groups in the benzofuranone moiety and the presence of bromine atoms in the benzene ring had a strong influence on the fluorescence behaviour of the aurones...
June 21, 2017: Photochemical & Photobiological Sciences
Miffy H Y Cheng, Huguette Savoie, Francesca Bryden, Ross W Boyle
Fluorescence is an essential imaging modality for labelling and visualising cells and sub-cellular structures. Multicolour labelling is especially challenging due to differences in physicochemical and photophysical behaviour of structurally unrelated fluorophores in the heterogeneous environments found in sub-cellular compartments. Herein, we report the conjugation of three azide-bearing BODIPYs with similar core structures but widely different emission wavelengths (green, red and NIR) to tyrosine residues of a model globular protein (BSA) via a common linking methodology...
June 21, 2017: Photochemical & Photobiological Sciences
G Checcucci, B Storti, F Ghetti, G Signore, R Bizzarri
The step-up photophobic response of the heterotrich ciliate Blepharisma japonicum is mediated by a hypericinic pigment, blepharismin, which is not present in any of the known six families of photoreceptors, namely rhodopsins, phytochromes, xanthopsins, cryptochromes, phototropins, and BLUF proteins. Upon irradiation, native cells become light-adapted (blue) by converting blepharismin into the photochemically stable oxyblepharismin (OxyBP). So far, OxyBP has been investigated mainly from a photophysical point of view in vitro, either alone or complexed with proteins...
June 21, 2017: Photochemical & Photobiological Sciences
Oleg V Chashchikhin, Mikhail F Budyka
The spectral and photochemical properties of hybrid organic-inorganic nanosystems (HNSs) were investigated. HNS consisted of CdS quantum dots (QDs) functionalized with ligands containing the isothiouronium anchor group linked by a polymethylene chain with photochromic merocyanine (MC). The HNS synthesis was carried out via a microwave-assisted one-pot technique. Energy transfer from the QDs to MC in the HNS was observed and resulted in QD fluorescence quenching and MC sensitization. Compared to the free MC, trans-cis photoisomerization of MC in the HNS was suppressed and its photodestruction was accelerated...
June 15, 2017: Photochemical & Photobiological Sciences
Elodie Merlier, Gabriel Hmimina, Matthieu Bagard, Eric Dufrêne, Kamel Soudani
Assessing photosynthesis rates with remote sensing is important for tracking the physiological state of plants. The photochemical reflectance index (PRI) is a good estimator of short-term light-use efficiency (LUE) at the leaf scale but its responses to environmental factors are poorly understood. In this study, we assessed changes in the responses of the PRI to ozone exposure and to an increase in atmospheric drought (separately and combined) in oak (Quercus robur) and holm oak (Quercus ilex) that were planted in climatic cells under controlled conditions...
June 15, 2017: Photochemical & Photobiological Sciences
Karina P Morelli Frin, Rafael M de Almeida
Mono-nuclear fac-[Re(CO)3(ph2phen)(4,4'-bpy)](+) and di-nuclear [(ph2phen)(CO)3Re(4,4'-bpy)Re(ph2phen)(CO)3](2+) complexes, ph2phen = 4,7-diphenyl-1,10-phenanthroline and 4,4'-bpy = 4,4'-bipyridine, were synthesized and characterized by (1)H NMR, UV-visible and FT-IR spectroscopy. Also, their photophysical properties were investigated using steady-state and time-resolved emission spectroscopy. Both complexes showed UV absorption assigned to intraligand, (1)ILph2phen, and metal-to-ligand charge transfer, (1)MLCTRe→ph2phen, transitions, and typical (3)MLCTRe→ph2phen emission (ϕ = 0...
June 14, 2017: Photochemical & Photobiological Sciences
Zhijie Zhang, Hui Liu, Jiayue Xu, Na Zhang
In order to utilize solar light more efficiently, a Bi2WO6 photocatalyst was sensitized by Cu(ii) meso-tetra (4-carboxyphenyl) porphyrin (CuTCPP). The obtained CuTCPP/Bi2WO6 composite exhibited enhanced photocatalytic activity in the degradation of an organic pollutant, rhodamine B (RhB), under simulated solar light irradiation as well as visible light beyond the absorption edge of Bi2WO6 (λ > 450 nm). The enhancement of the photocatalytic activity can be attributed to the sensitization effect of CuTCPP, which increased the visible-light harvesting, as well as the well-matched overlapping band structures between CuTCPP and Bi2WO6, which facilitated the separation of photo-generated electron-hole pairs...
June 14, 2017: Photochemical & Photobiological Sciences
A C Gonçalves, J Luis Capelo, C Lodeiro, A A Dos Santos
A new selenium containing coumarin (compound 7) was designed and synthesized from the amide linkage between coumarin-519 (6) and 2-(butylselanyl)ethanamine (5). The molecular structure of 7 was accurately characterized, and its photophysical properties in acetonitrile, ethanol and chloroform solutions were studied by absorption, stationary and time-resolved fluorescence spectroscopies. Changes in the solvent polarity affected the Stokes shift, quantum yields and lifetime of the excited states. The spectroscopic behavior of compound 7 was evaluated in the presence of different monovalent, divalent and trivalent metallic cations (Na(+), K(+), Ca(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Pb(2+), Hg(2+), Hg(+), Ag(+), Al(3+), Fe(3+), Ga(3+) and Cr(3+)) in acetonitrile solution...
June 12, 2017: Photochemical & Photobiological Sciences
Giulio Sturaro, Giulia Cigolini, Luca Menilli, Fabio Cola, Rosa Di Liddo, Alessia Tasso, Maria Teresa Conconi, Giorgia Miolo
The use of photoactivatable 8-methoxypsoralen (8-MOP) as potential focal treatment towards prostate cancer cells is proposed here. Our results, obtained on isolated DNA and DU145 cells, indicate that blue light, besides UVA, is able to activate 8-MOP. When compared to UVA, blue light irradiation led to a modulation of the extent and the types of 8-MOP-DNA damage, specially cross-links, coupled to a still valuable antiproliferative effect. Our data suggest that the proapototic activity of 8-MOP is related not only to DNA damage and reactive oxygen species generation but also to the modulation of cell signalling pathways...
June 12, 2017: Photochemical & Photobiological Sciences
Qian-Zhao Xu, Qi-Ying Tang, Jia-Xin Han, Wen-Long Ding, Bao-Qing Zhao, Ming Zhou, Wolfgang Gärtner, Hugo Scheer, Kai-Hong Zhao
Cyanobacterial phycobilisomes funnel the harvested light energy to the reaction centers via two terminal emitters, allophycocyanin B and the core-membrane linker. ApcD is the α-subunit of allophycocyanin B responsible for its red-shifted absorbance (λmax 665 nm). Far-red photo-acclimated cyanobacteria contain certain allophycocyanins that show even further red-shifted absorbances (λmax > 700 nm). We studied the chromophorylation of the three far-red induced ApcD subunits ApcD2, ApcD3 and ApcD4 from Chroococcidiopsis thermalis sp...
June 8, 2017: Photochemical & Photobiological Sciences
Renata M Martinez, Felipe A Pinho-Ribeiro, Vinicius S Steffen, Carla V Caviglione, Victor Fattori, Allan J C Bussmann, Carolina Bottura, Maria J V Fonseca, Josiane A Vignoli, Marcela M Baracat, Sandra R Georgetti, Waldiceu A Verri, Rubia Casagrande
trans-Chalcone is a plant flavonoid precursor, which lacks broad investigation on its biological activity in inflammatory processes. In the present study, anti-inflammatory and antioxidant mechanisms of systemic administration with trans-chalcone, a flavonoid precursor, on ultraviolet (UV) irradiation-induced skin inflammation and oxidative stress in hairless mice were investigated by the following parameters: skin edema, myeloperoxidase activity (neutrophil marker), matrix metalloproteinase-9 activity, reduced glutathione levels, catalase activity, lipid peroxidation products, superoxide anion production, gp(91phox) (NADPH oxidase subunit) mRNA expression by quantitative PCR and cytokine production by ELISA...
June 8, 2017: Photochemical & Photobiological Sciences
Anand S Dixit, Namram S Singh, Iadalangki Bamon
Experiments were performed on the subtropical tree sparrow (Passer montanus) to investigate the involvement of an endogenous circadian rhythm in photoperiodic time measurement during the initiation of gonadal growth and functions and also to study the photic entrainment of the circadian activity rhythm. Groups of photosensitive birds of both sexes were exposed to different "night-interruption" light-dark regimes of 24 h duration viz., G1 - 6L/5D/1L/12D, G2 - 6L/6D/1L/11D, G3 - 6L/7D/1L/10D, G4 - 6L/8D/1L/9D, G5 - 6L/10D/1L/7D, G6 - 6L/12D/1L/5D, G7 - 6L/14D/1L/3D and G8 - 6L/16D/1L/1D for 30 days in which 17 h long nights were interrupted by 1 h light pulse falling at different ZTs (i...
June 7, 2017: Photochemical & Photobiological Sciences
Chantal Carayon, Suzanne Fery-Forgues
The derivatives of 2-phenylbenzoxazole (PBO) are popular fluorescent organic dyes for use in solution or after dispersion in an appropriate matrix. Their spectroscopic behavior in the solid state is, unjustly, not so well known. Many of them are strongly emissive as pure solid dyes, due to a favorable crystal packing mode. The PBO fragment lends itself well to relatively simple modifications of its chemical structure, aimed at enlarging the conjugated π-electron system. Many molecules thus designed show aggregation-induced emission (AIE)...
June 5, 2017: Photochemical & Photobiological Sciences
Mikhail N Khimich, Vladimir L Ivanov, Mikhail Ya Melnikov, Ivan V Shelaev, Fedor E Gostev, Victor A Nadtochenko, Boris M Uzhinov
It was found that cations formed by the protonation of 2-amino-3-(2'-benzoxazolyl)-quinoline (ABO) and 2-amino-3-(2'-benzothiazolyl)-quinoline (ABT) at the nitrogen atom of the quinoline ring exhibit excited-state intramolecular proton transfer (ESIPT). The two-band fluorescence of these cations is due to the emission from two species: the initial tautomer (short-wavelength band) and the ESIPT product (long-wavelength band). The relative intensity of the long-wavelength band depends on the basicity of the proton-accepting moiety and temperature...
June 5, 2017: Photochemical & Photobiological Sciences
Amarja P Naik, Akshay V Salkar, Mahesh S Majik, Pranay P Morajkar
The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO2 under sunlight. Mesoporous anatase TiO2 of a high photocatalytic activity has been synthesized using a sol-gel method and its photocatalytic activity for the degradation of Amaranth dye has been evaluated with respect to Degussa P25. The effect of bi-dentate complexing agents like oxalic acid, ethylene glycol and urea on the surface properties of TiO2 catalyst has been investigated using TG-DTA, FTIR, HR-TEM, SAED, PXRD, EDS, UV-DRS, PL, BET N2 adsorption-desorption isotherm studies and BJH analysis...
May 26, 2017: Photochemical & Photobiological Sciences
D E Orallo, S G Bertolotti, M S Churio
The properties and photochemical and photophysical behavior of the mycosporine-like amino acids (MAAs) shinorine and porphyra-334 were experimentally evaluated in solutions of direct ionic micelles as simple biomimicking environments. The preferential partition of the natural molecules in the aqueous phase of sodium dodecyl sulfate (SDS) or cetyltrimethylammonium chloride (CTAC) micellar systems is confirmed. Although the proton dissociation of the carboxylic groups in the MAAs is slightly inhibited in CTAC solutions, the molecules are predicted to be in the form of zwitterions in all the explored media around physiological pH...
May 26, 2017: Photochemical & Photobiological Sciences
Pawan Kumar, Anurag Kumar, Clémence Queffélec, Dietrich Gudat, Qi Wang, Suman L Jain, Rabah Boukherroub, Sabine Szunerits
Hydrogen is considered to be an ideal energy carrier, which produces only water when combined with oxygen and thus has no detrimental effect on the environment. While the catalytic decomposition of hydrous hydrazine for the production of hydrogen is well explored, little is known about its photocatalytic decomposition. The present paper describes a highly efficient photochemical methodology for the production of hydrogen through the decomposition of aqueous hydrazine using titanium dioxide nanoparticles modified with a Rh(i) coordinated catechol phosphane ligand (TiO2-Rh) as a photocatalyst under visible light irradiation...
May 26, 2017: Photochemical & Photobiological Sciences
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