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Photochemistry and Photobiology

Roger Bresolí-Obach, Luis Busto-Moner, Claudia Muller, Manuel Reina, Santi Nonell
A biocompatible fluorescent nanoprobe for detection of reactive oxygen species in biological systems has been designed, synthesized, and characterized, circumventing some of the limitations of the molecular probe diacetyl 2',7'-dichlorodihydrofluorescein (DCFH-DA). It has been synthetized the nanoparticulate form of DCFH-DA by covalently attaching the widely-used fluorescent probe DCFH-DA to a mesoporous silica nanoparticle through a linker. The reactivity of nanoDCFH-DA has been tested towards several reactive oxygen species...
September 21, 2018: Photochemistry and Photobiology
Aline B de P Abrantes, Gustavo C Dias, Nadja C de Souza-Pinto, Mauricio S Baptista
The p53 protein exerts fundamental roles in cell responses to a variety of stress stimuli. It has clear roles in controlling cell cycle, triggering apoptosis, activating autophagy, and modulating DNA damage response. Little is known about the role of p53 in autophagy-associated cell death, which can be induced by photoactivation of photosensitizers within cells. The photosensitizer 1,9-dimethyl methylene blue (DMMB) within nanomolar concentration regimes has specific intracellular targets (mitochondria and lysosomes), photoinducing a typical scenario of cell death with autophagy...
September 21, 2018: Photochemistry and Photobiology
Jasvir Kaur, Neetu Singh Yadav, Moirangthem Kiran Singh, Mohd Jahir Khan, Sobhan Sen, Aparna Dixit, Devapriya Choudhury
The photophysics of Green Fluorescent Protein (GFP) is remarkable because of its exceptional property of Excited State Proton Transfer (ESPT) and the presence of a functional proton-wire. Another interesting property of wild type GFP is that its absorption and fluorescence excitation spectra are sensitive to the presence of polar organic solvents even at very low concentrations. Here we use a combination of methodologies including site specific mutagenesis, absorption spectroscopy, steady state and time resolved fluorescence measurements as well as all atom molecular dynamics simulations in explicit solvent, to uncover the mechanism behind the unique spectral sensitivity of GFP towards organic solvents...
September 21, 2018: Photochemistry and Photobiology
Tomáš Polívka
Mimicking light-harvesting and photoprotective processes of natural photosynthesis by artificial supramolecular systems is of considerable interest for artificial photosynthesis. The authors of the highlighted paper report on synthesis and spectroscopic characterization of a novel Pd-phthalocyanine-carotenoid dyads that allow to directly follow the triplet-triplet energy transfer between Pd-phthalocyanine and carotenoid. Unexpectedly, the T-T energy transfer do not follow the dependence on conjugation length of the acceptor carotenoid...
September 21, 2018: Photochemistry and Photobiology
Michael Pigula, Huang-Chiao Huang, Srivalleesha Mallidi, Sriram Anbil, Joyce Liu, Zhiming Mai, Tayyaba Hasan
Longitudinal monitoring of tumor size in vivo can provide important biological information about disease progression and treatment efficacy that is not captured by other modes of quantification. Ultrasound enables high throughput evaluation of orthotopic mouse models via fast acquisition of three-dimensional tumor images and calculation of volume with a reasonable degree of accuracy. Herein, we compare orthotopic pancreatic tumor volume measurements determined by ultrasound with volume measured by calipers and tumor weight, and found strong correlations between the three modalities over a large range of tumor sizes, suggesting ultrasound can accurately quantify tumor volumes in this model...
September 19, 2018: Photochemistry and Photobiology
M Moosavifar, S Bagheri
In this work, neat and supported H6 P2 W18 O62 into nanocage of β-zeolite were synthesized. However, H6 P2 W18 O62 into nanocage of β-zeolite was synthesized via template synthesis method. In addition, TiO2 was supported on H6 P2 W18 O62 /β zeolite by impregnation method. The obtained materials were characterized by XRD, FT-IR, UV-Vis, FESEM and EDS techniques. Also, W and Ti contents of the catalyst were determined by ICP and EDS technique. The results reveal that the photocatalyst performance depends on catalyst loading, pH effect, and methyl orange concentration...
September 17, 2018: Photochemistry and Photobiology
Dylan M Brown, Jianzhong Yang, Edward W Strach, Mohammed I Khalil, David G Whitten
Cationic polythiophenes have been shown to be potent antimicrobial compounds due to their ability to absorb visible light and sensitize the production of reactive oxygen species (ROS) as well as their ability to selectively associate with and damage negatively charged cell envelopes. This study demonstrates the ability of differentially sized imidazolium and tertiary amine functionalized poly(3-hexylthiophene) (P3HT) to inactivate Gram-negative Escherichia coli and Gram-positive Bacillus atrophaeus under photolysis and dark conditions...
September 17, 2018: Photochemistry and Photobiology
Md Ashraful Islam, John Beardall, Perran Cook
Stratospheric ozone depletion is mostly marked over the Antarctic and to a lesser extent over the Arctic, though recent reports have revealed that this also occurs at lower latitudes. Continued depletion of ozone in the lower stratosphere allows more UVR to reach the Earth's surface. Furthermore, it is projected that surface water temperatures will increase by between 0.2 and 2.0 °C by the year 2060 and this will directly or indirectly influence algal growth. The interactions between environmental factors are complicated by the existence of different strains (ecotypes) of the same species that may respond differently...
September 17, 2018: Photochemistry and Photobiology
Susan Monro, Colin G Cameron, Xiaolin Zhu, Katsuya L Colón, Huimin Yin, Tariq Sainuiddin, Marc Hetu, Mitch Pinto, Anderson Fuller, Leah Bennett, John Roque, Wenfang Sun, Sherri A McFarland
Three new bis(2,2'-bipyridine)-heteroleptic Ru(II) dyads incorporating thienyl groups (n=1-3, compounds 1, 2, and 3, respectively) appended to 1,10-phenanthroline were synthesized and characterized to investigate the impact of n on the photophysical and photobiological properties within the series. All three complexes showed unstructured emission near 618 nm from a triplet metal-to-ligand charge transfer (3 MLCT) state with a lifetime (τem ) of approximately 1 μs. Transient absorption measurements revealed an additional excited state that was nonemissive and long-lived (τTA =43 μs for 2 and 27 μs for 3), assigned as a triplet intraligand (3 IL) state that was accessible only in 2 and 3...
September 7, 2018: Photochemistry and Photobiology
Amanda Bard, Rebeca Rondon, Daniela T Marquez, Anabel E Lanterna, Juan C Scaiano
Kinetics of gold-nanoparticle-surface modification with thiols can take more than one hour for completion. 7-Mercapto-4-methylcoumarin, can be used to follow the process by fluorescence spectroscopy and serves as a convenient molecular probe to determine relative kinetics of other thiol compounds. SERS studies with aromatic thiols further support the slow surface modification kinetics observed by fluorescence spectroscopy. The formation of thiolate bonds is a relatively slow process; we recommend one to two hour wait for thiol binding to be essentially complete, while for disulfides, overnight incubation is suggested...
September 7, 2018: Photochemistry and Photobiology
B Dexter, R King, S L Harrison, A V Parisi, N J Downs
Melanoma skin cancer rates in Queensland exceed the national Australian incidence rate, which together with New Zealand are recognised as the world's highest. Incidence is especially high among younger members of the population. In this study, the sun-protective behaviours of urban Queenslanders (n = 752) going about their day-to-day activities during a mid-week noon time hourly period were observed on a summer's day in central Brisbane (27.47° S, 153.03° E), Australia. Observed sun protection practices were poor, given the time of year and peak solar noon-period of the study...
September 7, 2018: Photochemistry and Photobiology
Mahlako Malesele Nkogatse, Motsehoa Cynthia Ramotsehoa, Frederick Christofel Eloff, Caradee Yael Wright
The exposure of outdoor car guards to solar ultraviolet radiation (UVR), the majority with deeply-pigmented skin, to solar UVR was measured for five consecutive days during early spring (September 2017) in South Africa using electronic UVR dosimeters attached to the upper arm of each participant. The exposure of the nape of the neck, forehead, nose, cheek and hand were extrapolated from the measurements. The onsite ambient solar UVR on a flat, horizontal, unshaded surface was measured concurrently. The sun-related knowledge, behaviour and attitudes of the car guards were evaluated using questionnaires...
September 5, 2018: Photochemistry and Photobiology
Anu Mishra, Bhupendra Singh Butola
In this study, titanium tetra isopropoxide was used as pre-cursor of TiO2 for in-situ coating on cotton fabric by sol-gel-method. Subsequently, silver nitrate was used as doping agent to prepare silver doped TiO2 coated cotton fabric during hydrothermal treatment. The treated samples were characterized through Field Emission Scanning Electron Microscopy (FE-SEM), Energy-Dispersive X-ray (EDX) analysis, Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) and UV-visible Absorption Spectroscopy to study morphology, composition of deposited elements and light absorption behavior of treated samples...
September 5, 2018: Photochemistry and Photobiology
Shiji Mathew, R Aswani, Jyothis Mathew, E K Radhakrishnan
Green synthesised silver nanoparticles (AgNPs) have enormous applications. Hence there is an increasing demand to explore diverse bioresources for AgNP fabrication to make the process more cost effective and rapid as possible. Due to the abundantly present hydroxyl groups of rice starch, it provides ideal sites for metal ion complexation and thereby synthesis of nanoparticles with promising activity. So the study was designated to develop rapid, eco-friendly and cost effective method for green AgNPs synthesis using boiled rice water starch in presence of sunlight irradiation...
August 30, 2018: Photochemistry and Photobiology
Huizhi Zhao, Shiyong Wu
Nitric oxide (NO• ) plays an important role in regulation of redox balance in keratinocytes post-UVB exposure. Since endothelial cells releases NO• for a prolonged time post-UVB, we determined whether HUVEC could have an effect on UVB-induced DNA damage and transformation of their adjacent keratinocytes (HaCaT) using a 3D cell co-culturing system. Our data shows that the levels of DNA breaks and/or cyclobutane pyrimidine dimer (CPD) along with γH2AX are higher in the co-cultured than in the mono-cultured keratinocytes post-UVB...
August 30, 2018: Photochemistry and Photobiology
Caradee Y Wright, Robyn M Lucas, Catherine D'Este, Thandi Kapwata, Zamantimande Kunene, Ashwin Swaminathan, Angela Mathee, Patricia N Albers
The incidence of many serious childhood infections can be reduced by vaccination. High sun exposure at the time of vaccination has been associated with a reduced antigen-specific immune response. We hypothesised that providing sun protection advice and equipment to mothers of children who were waiting to be vaccinated would result in a more robust immunisation response. We conducted a pilot study in 2015/2016 (data analysed in 2017-2018) among 98 Black African children (~18 months of age) receiving the booster measles vaccination at two clinics in South Africa...
August 29, 2018: Photochemistry and Photobiology
E Ann Holmes, Rachael M Rodney Harris, Robyn M Lucas
The incidence and prevalence of inflammatory bowel disease (IBD) are increasing worldwide. Some ecological studies show increasing incidence with increasing latitude. Ambient ultraviolet radiation varies inversely with latitude, and sun exposure of the skin is a major source of vitamin D. Vitamin D deficiency is common in patients with IBD. Sun exposure and vitamin D have immune effects that could plausibly reduce, or be protective for, IBD. One quarter of new IBD cases are diagnosed in childhood or adolescence, but most research is for adult-onset IBD...
August 29, 2018: Photochemistry and Photobiology
Ana Luiza Ribeiro de Souza, Kayla Marra, Jason Gunn, Kimberley S Samkoe, Sally Hull, Keith D Paulsen, Brian W Pogue
Since many types of cancers overexpress EGFR, this surface receptor has been used as a target for therapy or diagnosis of malignant disease. Uptake kinetics of EGFR-targeted fluorescent Affibody (ABY-029) were studied with a view toward optimizing efficacy of tumor detection in a glioma as a function of both delivered dose and concurrent administration of unlabeled cetuximab (an EGFR antagonist). U251 glioma cells were inoculated in brain of nude rats and the fluorescence from each brain was analyzed after administration of ABY-029...
August 21, 2018: Photochemistry and Photobiology
Girgis Obaid, Wendong Jin, Shazia Bano, David Kessel, Tayyaba Hasan
With the rapidly emerging designs and applications of light-activated, photodynamic therapy (PDT)-based nanoconstructs, photonanomedicines (PNMs), an unmet need exists to establish whether conventional methods of photochemical and photophysical characterization of photosensitizers are relevant for evaluating new PNMs in order to intelligently guide their design. As a model system, we build on the clinical formulation of benzoporphyrin derivative (BPD), Visudyne® , by developing a panel of nanolipid formulations entrapping new lipidated chemical variants of BPD with differing chemical, photochemical and photophysical properties...
August 20, 2018: Photochemistry and Photobiology
Christian Brückner
The photoacoustic effect - the generation of a sound wave upon absorption of light by a sample, was developed over the past decades into photoacoustic imaging (PAI), and related technologies. These imaging modalities combine the advantages of optical imaging techniques (high resolution) with those of ultrasonic imaging (deep imaging depth). The light absorption by a tissue sample can be because of endogenous absorbers (such as hemoglobin or melanins). Alternatively-and most advantageously-is the use of exogenous dyes as contrast agents...
August 20, 2018: Photochemistry and Photobiology
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