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https://www.readbyqxmd.com/read/28631802/aqueous-tantalum-polyoxometalate-reactivity-with-peroxide
#1
Lauren B Fullmer, Christopher E Malmberg, Dylan B Fast, Lindsay A Wills, Paul Ha-Yeon Cheong, Michelle R Dolgos, May Nyman
Peroxide ligation of aqueous metal-oxo clusters provides rich speciation and structural diversity, radiation sensitivity for manipulation with light, and both broadens and shifts pH-range stability. Here we demonstrate peroxide ligation of the polyoxometalate (POM) [Ta6O19](8-). We study in detail solution speciation of the peroxide-substituted cluster, and benchmark it to the peroxide-ligated niobate analogue, [Nb6O10(OH)3(O2)6](5-), whose solid-state structure has been reported. Raman and electrospray ionization mass spectroscopy do not detect any significant differences between the two analogues...
June 20, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28628332/watson-crick-base-pair-radical-cation-as-a-model-for-oxidative-damage-in-dna
#2
Linda Feketeova, Bun Chan, George N Khairallah, Vincent Steinmetz, Philippe Maître, Leo Radom, Richard A J O'Hair
The deleterious cellular effects of ionizing radiation are well known but the mechanisms causing DNA damage are poorly understood. The accepted molecular events involve initial oxidation and deprotonation at guanine sites, triggering hydrogen-atom-abstraction reactions from the sugar moieties, causing DNA strand breaks. Probing the chemistry of the initially formed radical cation has been challenging. Here we generate, spectroscopically characterise and examine the reactivity of the Watson-Crick nucleobase-pair radical cation in the gas-phase...
June 19, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28618830/acoustic-levitation-of-an-object-larger-than-the-acoustic-wavelength
#3
Marco A B Andrade, Fábio T A Okina, Anne L Bernassau, Julio C Adamowski
Levitation and manipulation of objects by sound waves have a wide range of applications in chemistry, biology, material sciences, and engineering. However, the current acoustic levitation techniques are mainly restricted to particles that are much smaller than the acoustic wavelength. In this work, it is shown that acoustic standing waves can be employed to stably levitate an object much larger than the acoustic wavelength in air. The levitation of a large slightly curved object weighting 2.3 g is demonstrated by using a device formed by two 25 kHz ultrasonic Langevin transducers connected to an aluminum plate...
June 2017: Journal of the Acoustical Society of America
https://www.readbyqxmd.com/read/28617676/interactions-between-low-energy-electrons-and-dna-a-perspective-from-first-principles-simulations
#4
Jorge Jose Kohanoff, Maeve McAllister, Gareth Tribello, Bin Gu
DNA damage caused by irradiation has been studied for many decades. Such studies allow us to better assess the dangers posed by radiation, and to increase the efficiency of the radiotherapies that are used to combat cancer. A full description of the irradiation process involves multiple size and time scales. It starts from the interaction of radiation -- either photons or swift ions -- with the biological medium. Such interactions cause electronic excitation and ionisation. The two main products of ionising radiation are thus electrons and radicals...
June 15, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28614348/organic-compounds-in-fluid-inclusions-of-archean-quartz-analogues-of-prebiotic-chemistry-on-early-earth
#5
Ulrich Schreiber, Christian Mayer, Oliver J Schmitz, Pia Rosendahl, Amela Bronja, Markus Greule, Frank Keppler, Ines Mulder, Tobias Sattler, Heinz F Schöler
The origin of life is still an unsolved mystery in science. Hypothetically, prebiotic chemistry and the formation of protocells may have evolved in the hydrothermal environment of tectonic fault zones in the upper continental crust, an environment where sensitive molecules are protected against degradation induced e.g. by UV radiation. The composition of fluid inclusions in minerals such as quartz crystals which have grown in this environment during the Archean period might provide important information about the first organic molecules formed by hydrothermal synthesis...
2017: PloS One
https://www.readbyqxmd.com/read/28598469/interfacial-photochemistry-of-biogenic-surfactants-a-major-source-of-abiotic-volatile-organic-compounds
#6
Martin Brüggemann, Nathalie Hayeck, Chloé Bonnineau, Stéphane Pesce, Peter A Alpert, Sébastien Perrier, Christoph Zuth, Thorsten Hoffmann, Jianmin Chen, Christian George
Films of biogenic compounds exposed to the atmosphere are ubiquitously found on the surfaces of cloud droplets, aerosol particles, buildings, plants, soils and the ocean. These air/water interfaces host countless amphiphilic compounds concentrated there with respect to in bulk water, leading to a unique chemical environment. Here, photochemical processes at the air/water interface of biofilm-containing solutions were studied, demonstrating abiotic VOC production from authentic biogenic surfactants under ambient conditions...
June 9, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28591856/a-brief-overview-of-compartmental-modeling-for-intake-of-plutonium-via-wounds
#7
D Poudel, J A Klumpp, T L Waters, L Bertelli, R A Guilmette
The aim of this study is to present several approaches that have been used to model the behavior of radioactive materials (specifically Pu) in contaminated wounds. We also review some attempts by the health physics community to validate and revise the National Council on Radiation Protection and Measurements (NCRP) 156 biokinetic model for wounds, and present some general recommendations based on the review. Modeling of intake via the wound pathway is complicated because of a large array of wound characteristics (e...
June 7, 2017: Radiation Protection Dosimetry
https://www.readbyqxmd.com/read/28559347/three-classes-of-oxygen-dependent-cyclase-involved-in-chlorophyll-and-bacteriochlorophyll-biosynthesis
#8
Guangyu E Chen, Daniel P Canniffe, C Neil Hunter
The biosynthesis of (bacterio)chlorophyll pigments is among the most productive biological pathways on Earth. Photosynthesis relies on these modified tetrapyrroles for the capture of solar radiation and its conversion to chemical energy. (Bacterio)chlorophylls have an isocyclic fifth ring, the formation of which has remained enigmatic for more than 60 y. This reaction is catalyzed by two unrelated cyclase enzymes using different chemistries. The majority of anoxygenic phototrophic bacteria use BchE, an O2-sensitive [4Fe-4S] cluster protein, whereas plants, cyanobacteria, and some phototrophic bacteria possess an O2-dependent enzyme, the major catalytic component of which is a diiron protein, AcsF...
June 13, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28559340/microlayer-source-of-oxygenated-volatile-organic-compounds-in-the-summertime-marine-arctic-boundary-layer
#9
Emma L Mungall, Jonathan P D Abbatt, Jeremy J B Wentzell, Alex K Y Lee, Jennie L Thomas, Marjolaine Blais, Michel Gosselin, Lisa A Miller, Tim Papakyriakou, Megan D Willis, John Liggio
Summertime Arctic shipboard observations of oxygenated volatile organic compounds (OVOCs) such as organic acids, key precursors of climatically active secondary organic aerosol (SOA), are consistent with a novel source of OVOCs to the marine boundary layer via chemistry at the sea surface microlayer. Although this source has been studied in a laboratory setting, organic acid emissions from the sea surface microlayer have not previously been observed in ambient marine environments. Correlations between measurements of OVOCs, including high levels of formic acid, in the atmosphere (measured by an online high-resolution time-of-flight mass spectrometer) and dissolved organic matter in the ocean point to a marine source for the measured OVOCs...
June 13, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28540940/modelling-charge-transfer-processes-in-c-2-tetrahydrofuran-collision-for-ion-induced-radiation-damage-in-dna-building-blocks
#10
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
#11
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
#12
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
#13
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 30, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28508574/isomer-selective-generation-and-spectroscopic-characterization-of-picolyl-radicals
#14
Engelbert Reusch, Fabian Holzmeier, Philipp Constantinidis, Patrick Hemberger, Ingo Fischer
Nitrogen-containing resonance-stabilized radicals such as the picolyl radical are important in combustion chemistry and astrochemistry. They have only been scarcely studied because an isomer-selective generation is often difficult. Herein, we present threshold photoelectron spectra of the three picolyl radical isomers, C6 H6 N, that were obtained with synchrotron radiation. The radicals were selectively generated by flash pyrolysis from aminomethylpyridine precursors through deamination. Ionization energies of 7...
June 26, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28508051/genuine-binding-energy-of-the-hydrated-electron
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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