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https://www.readbyqxmd.com/read/28540940/modelling-charge-transfer-processes-in-c-2-tetrahydrofuran-collision-for-ion-induced-radiation-damage-in-dna-building-blocks
#1
Ewa Erdmann, Marie-Christine Bacchus-Montabonel, Marta Łabuda
Investigations of collision-induced processes involving carbon ions and molecules of biological interest, in particular DNA building blocks, are crucial to model the effect of radiation on cells in order to improve medical treatments for cancer therapy. Using carbon ions appears to be one of the most efficient ways to increase biological effectiveness to damage cancerous cells by irradiating deep-seated tumors. Therefore, interest in accurate calculations to understand fundamental processes occurring in ion-molecule collision systems has been growing recently...
May 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28537771/atmospheric-constraints-on-the-surface-uv-environment-of-mars-at-3-9%C3%A2-ga-relevant-to-prebiotic-chemistry
#2
Sukrit Ranjan, Robin Wordsworth, Dimitar D Sasselov
Recent findings suggest that Mars may have been a clement environment for the emergence of life and may even have compared favorably to Earth in this regard. These findings have revived interest in the hypothesis that prebiotically important molecules or even nascent life may have formed on Mars and been transferred to Earth. UV light plays a key role in prebiotic chemistry. Characterizing the early martian surface UV environment is key to understanding how Mars compares to Earth as a venue for prebiotic chemistry...
May 24, 2017: Astrobiology
https://www.readbyqxmd.com/read/28536987/sexual-deception-in-the-eucera-pollinated-ophrys-leochroma-a-chemical-intermediate-between-wasp-and-andrena-pollinated-species
#3
Monica Cuervo, Demetra Rakosy, Carlos Martel, Stefan Schulz, Manfred Ayasse
Ophrys flowers mimic sex pheromones of attractive females of their pollinators and attract males, which attempt to copulate with the flower and thereby pollinate it. Virgin females and orchid flowers are known to use the same chemical compounds in order to attract males. The composition of the sex pheromone and its floral analogue, however, vary between pollinator genera. Wasp-pollinated Ophrys species attract their pollinators by using polar hydroxy acids, whereas Andrena-pollinated species use a mixture of non-polar hydrocarbons...
May 23, 2017: Journal of Chemical Ecology
https://www.readbyqxmd.com/read/28524209/understanding-the-biomimetic-properties-of-gallium-in-pseudomonas-aeruginosa-an-xas-and-xps-study
#4
F Porcaro, C Bonchi, A Ugolini, E Frangipani, G Polzonetti, P Visca, C Meneghini, C Battocchio
Pyochelin (PCH) is a siderophore (extracellular chelator) produced by the pathogenic bacterium Pseudomonas aeruginosa (PAO). PCH is implicated in iron (Fe(3+)) transport to PAO, and is crucial for its metabolism and pathogenicity. Due to the chemical similarity with Fe(3+), gallium (Ga(3+)) interferes with vital iron-dependent processes in bacterial cells, thereby opening new perspectives for the design of specific metal-based antibacterial drugs. However, the structural basis for the Fe(3+)-mimetic properties of Ga(3+) complexed with the PCH siderophore is still lacking...
May 19, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28508574/isomer-selective-generation-and-spectroscopic-characterization-of-picolyl-radicals
#5
Engelbert Reusch, Fabian Holzmeier, Philipp Constantinidis, Patrick Hemberger, Ingo Fischer
Nitrogen-containing resonance-stabilized radicals like picolyl are important in combustion chemistry and astrochemistry. They have only been scarcely studied, because an isomer-selective generation is often difficult. Here we present threshold photoelectron spectra of three picolyl radical isomers, C6H6N, using synchrotron radiation. The radicals were selectively generated by flash pyrolysis from aminomethylpyridine precursors via deamination. Ionization energies of 7.70 eV, 7.59 eV and 8.01 eV are determined for 2-, 3- and 4-picolyl, respectively...
May 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28508051/genuine-binding-energy-of-the-hydrated-electron
#6
David Luckhaus, Yo-Ichi Yamamoto, Toshinori Suzuki, Ruth Signorell
The unknown influence of inelastic and elastic scattering of slow electrons in water has made it difficult to clarify the role of the solvated electron in radiation chemistry and biology. We combine accurate scattering simulations with experimental photoemission spectroscopy of the hydrated electron in a liquid water microjet, with the aim of resolving ambiguities regarding the influence of electron scattering on binding energy spectra, photoelectron angular distributions, and probing depths. The scattering parameters used in the simulations are retrieved from independent photoemission experiments of water droplets...
April 2017: Science Advances
https://www.readbyqxmd.com/read/28492328/inhibition-of-radiolytic-molecular-hydrogen-formation-by-quenching-of-excited-state-water
#7
Gregory P Horne, Simon M Pimblott, Jay A LaVerne
Comparison of experimental measurements of the yield of molecular hydrogen produced in the gamma radiolysis of water and aqueous nitrate solutions with predictions of a Monte Carlo track chemistry model shows that the nitrate anion scavenging of the hydrated electron, its precursor, and hydrogen atom cannot account for the observed decrease in the yield at high nitrate anion concentrations. Inclusion of the quenching of excited states of water (formed by either direct excitation or reaction of the water radical cation with the precursor to the hydrated electron) by the nitrate anion into the reaction scheme provides excellent agreement between the stochastic calculations and experiment demonstrating the existence of this short-lived species and its importance in water radiolysis...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28471084/the-femtochemistry-of-a-ferracyclobutadiene
#8
Boris Wezisla, Jörg Lindner, Ujjal Das, Alexander C Filippou, Peter Vöhringer
The eminent role of metallacyclobutadienes as catalytic intermediates in organic synthesis and polymer chemistry is widely acknowledged. In contrast, their photochemistry is as yet entirely unexplored. Herein, the photo-induced primary processes of a ferracyclobutadiene tricarbonyl complex in solution are revealed by femtosecond mid-infrared spectroscopy. The time-resolved vibrational spectra expose an ultrafast substitution of a basal CO ligand by a solvent molecule in a consecutive dissociation-association mechanism...
May 4, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28443889/the-passivating-effect-of-cadmium-in-pbs-cds-colloidal-quantum-dots-probed-by-nm-scale-depth-profiling
#9
Pip C J Clark, Hanna Radtke, Atip Pengpad, Andrew I Williamson, Ben F Spencer, Samantha J O Hardman, Marina A Leontiadou, Darren C J Neo, Simon M Fairclough, Andrew A R Watt, Igor Pis, Silvia Nappini, Federica Bondino, Elena Magnano, Karsten Handrup, Karina Schulte, Mathieu G Silly, Fausto Sirotti, Wendy R Flavell
Achieving control of the surface chemistry of colloidal quantum dots (CQDs) is essential to fully exploit their properties in solar cells, but direct measurement of the chemistry and electronic structure in the outermost atomic layers is challenging. Here we probe the surface oxidation and passivation of cation-exchanged PbS/CdS core/shell CQDs with sub nm-scale precision using synchrotron-radiation-excited depth-profiling photoemission. We investigate the surface composition of the topmost 1-2.5 nm of the CQDs as a function of depth, for CQDs of varying CdS shell thickness, and examine how the surface changes after prolonged air exposure...
May 11, 2017: Nanoscale
https://www.readbyqxmd.com/read/28442137/enhanced-surface-ozone-during-the-heat-wave-of-2013-in-yangtze-river-delta-region-china
#10
X Pu, T J Wang, X Huang, D Melas, P Zanis, D K Papanastasiou, A Poupkou
Under the background of global warming, occurrence of heat waves has increased in most part of Europe, Asia and Australia along with enhanced ozone level. In this paper, observational air temperature and surface ozone in the Yangtze River Delta (YRD) region of China during summer of 2013, and the regional chemistry-climate model (RegCM-CHEM4) were applied to explore the relationship between heat wave and elevated ground-level ozone. Observations indicated that YRD experienced severe heat waves with maximum temperature up to 41...
April 22, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28431206/phase-transfer-ligand-exchange-of-lead-chalcogenide-quantum-dots-for-direct-deposition-of-thick-highly-conductive-films
#11
Qianglu Lin, Hyeong Jin Yun, Wenyong Liu, Hyung-Jun Song, Nikolay S Makarov, Oleksandr Isaienko, Tom Nakotte, Gen Chen, Hongmei Luo, Victor I Klimov, Jeffrey M Pietryga
The use of semiconductor nanocrystal quantum dots (QDs) in optoelectronic devices typically requires postsynthetic chemical surface treatments to enhance electronic coupling between QDs and allow for efficient charge transport in QD films. Despite their importance in solar cells and infrared (IR) light-emitting diodes and photodetectors, advances in these chemical treatments for lead chalcogenide (PbE; E = S, Se, Te) QDs have lagged behind those of, for instance, II-VI semiconductor QDs. Here, we introduce a method for fast and effective ligand exchange for PbE QDs in solution, resulting in QDs completely passivated by a wide range of small anionic ligands...
May 5, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28418703/radioresistance-of-adenine-to-cosmic-rays
#12
Gabriel S Vignoli Muniz, Christian F Mejía, Rafael Martinez, Basile Auge, Hermann Rothard, Alicja Domaracka, Philippe Boduch
The presence of nucleobases in carbonaceous meteorites on Earth is an indication of the existence of this class of molecules in outer space. However, space is permeated by ionizing radiation, which can have damaging effects on these molecules. Adenine is a purine nucleobase that amalgamates important biomolecules such as DNA, RNA, and ATP. Adenine has a unique importance in biochemistry and therefore life. The aim of this work was to study the effects of cosmic ray analogues on solid adenine and estimate its survival when exposed to corpuscular radiation...
April 2017: Astrobiology
https://www.readbyqxmd.com/read/28415861/atmospheric-aerosols-clouds-chemistry-and-climate
#13
V Faye McNeill
Although too small to be seen with the human eye, atmospheric particulate matter has major impacts on the world around us, from our health to global climate. Understanding the sources, properties, and transformations of these particles in the atmosphere is among the major challenges in air quality and climate research today. Significant progress has been made over the past two decades in understanding atmospheric aerosol chemistry and its connections to climate. Advances in technology for characterizing aerosol chemical composition and physical properties have enabled rapid discovery in this area...
April 17, 2017: Annual Review of Chemical and Biomolecular Engineering
https://www.readbyqxmd.com/read/28414388/infrared-spectroscopy-of-secondary-organic-aerosol-precursors-and-investigation-of-the-hygroscopicity-of-soa-formed-from-the-oh-reaction-with-guaiacol-and-syringol
#14
Waed Ahmad, Cecile Coeur, Alexandre Tomas, Thomas Fagniez, Jean-Blaise Brubach, Arnaud Cuisset
Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) synchrotron analyses supplemented by density functional theory (DFT) anharmonic calculations have been undertaken to study the fundamental vibrational signatures of guaiacol and syringol, two methoxyphenol compounds found at the highest concentrations in fresh wood smoke and precursors of secondary organic aerosols (SOA) affecting the radiative balance and chemistry of the atmosphere. Nitroderivatives of these two compounds have also been studied experimentally for nitroguaiacol and theoretically for nitrosyringol...
April 10, 2017: Applied Optics
https://www.readbyqxmd.com/read/28405645/a-new-model-of-the-chemistry-of-ionizing-radiation-in-solids-ciris
#15
Christopher N Shingledecker, Romane Le Gal, Eric Herbst
The collisions between high-energy ions and solids can result in significant physical and chemical changes to the material. These effects are potentially important for better understanding the chemistry of interstellar and planetary bodies, which are exposed to cosmic radiation and the solar wind, respectively; however, modeling such collisions on a detailed microscopic basis has thus far been largely unsuccessful. To that end, a new model, entitled CIRIS: the Chemistry of Ionizing Radiation in Solids, was created to calculate the physical and chemical effects of the irradiation of solid materials...
April 13, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28395111/highly-soluble-p-terphenyl-and-fluorene-derivatives-as-efficient-dopants-in-plastic-scintillators-for-sensitive-nuclear-material-detection
#16
Alan Sellinger, Henok A Yemam, Adam Mahl, Uwe Greife, Jonathan Tinkham, Joshua Koubek
Plastic scintillators are commonly used as first-line detectors for special nuclear materials. Current state-of-the-art plastic scintillators based on poly(vinyltoluene) (PVT) matrices containing high loadings (>15.0 wt%) of 2,5-diphenyloxazole (PPO) offer neutron signal discrimination in gamma radiation background (termed pulse shape discrimination, PSD), however they suffer from poor mechanical properties. In this work, a series of p-terphenyl and fluorene derivatives were synthesized and used as dopants in PVT based plastic scintillators as possible alternatives to PPO to address the mechanical property issue and to study the PSD mechanism...
April 10, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28375902/ergothioneine-antioxidant-function-from-chemistry-to-cardiovascular-therapeutic-potential
#17
Luigi Servillo, Nunzia DʼOnofrio, Maria Luisa Balestrieri
Ergothioneine (ESH), the betaine of 2-mercapto-L-histidine, is a water-soluble naturally occurring amino acid with antioxidant properties. ESH accumulates in several human and animal tissues up to millimolar concentration through its high affinity transporter, namely the organic cation transporter 1 (OCTN1). ESH, first isolated from the ergot fungus (Claviceps purpurea), is synthesized only by Actinomycetales and non-yeast-like fungi. Plants absorb ESH via symbiotic associations between their roots and soil fungi, whereas mammals acquire it solely from dietary sources...
April 2017: Journal of Cardiovascular Pharmacology
https://www.readbyqxmd.com/read/28375692/the-hydrated-electron
#18
John M Herbert, Marc P Coons
Existence of a hydrated electron as a byproduct of water radiolysis was established more than 50 years ago, yet this species continues to attract significant attention due to its role in radiation chemistry, including DNA damage, and because questions persist regarding its detailed structure. This work provides an overview of what is known in regards to the structure and spectroscopy of the hydrated electron, both in liquid water and in clusters [Formula: see text], the latter of which provide model systems for how water networks accommodate an excess electron...
May 5, 2017: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/28373709/the-signs-of-antarctic-ozone-hole-recovery
#19
Jayanarayanan Kuttippurath, Prijitha J Nair
Absorption of solar radiation by stratospheric ozone affects atmospheric dynamics and chemistry, and sustains life on Earth by preventing harmful radiation from reaching the surface. Significant ozone losses due to increases in the abundances of ozone depleting substances (ODSs) were first observed in Antarctica in the 1980s. Losses deepened in following years but became nearly flat by around 2000, reflecting changes in global ODS emissions. Here we show robust evidence that Antarctic ozone has started to recover in both spring and summer, with a recovery signal identified in springtime ozone profile and total column measurements at 99% confidence for the first time...
April 3, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28366679/o2-%C3%A2-and-h2o2-mediated-disruption-of-fe-metabolism-causes-the-differential-susceptibility-of-nsclc-and-gbm-cancer-cells-to-pharmacological-ascorbate
#20
Joshua D Schoenfeld, Zita A Sibenaller, Kranti A Mapuskar, Brett A Wagner, Kimberly L Cramer-Morales, Muhammad Furqan, Sonia Sandhu, Thomas L Carlisle, Mark C Smith, Taher Abu Hejleh, Daniel J Berg, Jun Zhang, John Keech, Kalpaj R Parekh, Sudershan Bhatia, Varun Monga, Kellie L Bodeker, Logan Ahmann, Sandy Vollstedt, Heather Brown, Erin P Shanahan Kauffman, Mary E Schall, Ray J Hohl, Gerald H Clamon, Jeremy D Greenlee, Matthew A Howard, Michael K Shultz, Brian J Smith, Dennis P Riley, Frederick E Domann, Joseph J Cullen, Garry R Buettner, John M Buatti, Douglas R Spitz, Bryan G Allen
Pharmacological ascorbate has been proposed as a potential anti-cancer agent when combined with radiation and chemotherapy. The anti-cancer effects of ascorbate are hypothesized to involve the autoxidation of ascorbate leading to increased steady-state levels of H2O2; however, the mechanism(s) for cancer cell-selective toxicity remain unknown. The current study shows that alterations in cancer cell mitochondrial oxidative metabolism resulting in increased levels of O2(⋅-) and H2O2 are capable of disrupting intracellular iron metabolism, thereby selectively sensitizing non-small-cell lung cancer (NSCLC) and glioblastoma (GBM) cells to ascorbate through pro-oxidant chemistry involving redox-active labile iron and H2O2...
April 10, 2017: Cancer Cell
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