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https://www.readbyqxmd.com/read/28731691/singlet-oxygen-photophysics-in-liquid-solvents-converging-on-a-unified-picture
#1
Mikkel Bregnhøj, Michael Westberg, Boris F Minaev, Peter R Ogilby
Singlet oxygen, O2(a(1)Δg), the lowest excited electronic state of molecular oxygen, is an omnipresent part of life on earth. It is readily formed through a variety of chemical and photochemical processes, and its unique reactions are important not just as a tool in chemical syntheses but also in processes that range from polymer degradation to signaling in biological cells. For these reasons, O2(a(1)Δg) has been the subject of intense activity in a broad distribution of scientific fields for the past ∼50 years...
July 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28723168/enhanced-room-temperature-oxygen-sensing-properties-of-laocl-sno2-hollow-spheres-by-uv-light-illumination
#2
Ya Xiong, Wenbo Lu, Degong Ding, Lei Zhu, Xiaofang Li, Cuicui Ling, Qingzhong Xue
In this paper, a facile and elegant Green Chemistry method for the synthesis of SnO2 based hollow spheres has been investigated. The influences of doping, crystallite morphology, and operating condition on the O2 sensing performances of SnO2 based hollow-sphere sensors were comprehensively studied. It was indicated that, compared with undoped SnO2, 10 at. % LaOCl-doped SnO2 possessed better O2 sensing characteristics owing to an increase of specific surface area and oxygen vacancy defect caused by LaOCl dopant...
May 26, 2017: ACS Sensors
https://www.readbyqxmd.com/read/28722734/scavenging-and-recombination-kinetics-in-radiation-chemistry
#3
Eyad H Al-Samra, Nicholas J B Green
This work describes stochastic models developed to study the competition between radical scavenging and recombination for simple model systems typical of radiation chemistry, where the reactive particles are tightly clustered and reactions are assumed fully diffusion limited. Three models are developed: a Monte Carlo random flights model with a periodic boundary condition for scavengers, Monte Carlo simulations in which the scavenging rate is calculated from the Smoluchowski theory for diffusion-limited reactions and a modification of the independent reaction times method where the scavengers close to the spur are explicitly included and the scavengers further away are treated as a continuum...
July 19, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28706325/axsis-exploring-the-frontiers-in-attosecond-x-ray-science-imaging-and-spectroscopy
#4
F X Kärtner, F Ahr, A-L Calendron, H Çankaya, S Carbajo, G Chang, G Cirmi, K Dörner, U Dorda, A Fallahi, A Hartin, M Hemmer, R Hobbs, Y Hua, W R Huang, R Letrun, N Matlis, V Mazalova, O D Mücke, E Nanni, W Putnam, K Ravi, F Reichert, I Sarrou, X Wu, A Yahaghi, H Ye, L Zapata, D Zhang, C Zhou, R J D Miller, K K Berggren, H Graafsma, A Meents, R W Assmann, H N Chapman, P Fromme
X-ray crystallography is one of the main methods to determine atomic-resolution 3D images of the whole spectrum of molecules ranging from small inorganic clusters to large protein complexes consisting of hundred-thousands of atoms that constitute the macromolecular machinery of life. Life is not static, and unravelling the structure and dynamics of the most important reactions in chemistry and biology is essential to uncover their mechanism. Many of these reactions, including photosynthesis which drives our biosphere, are light induced and occur on ultrafast timescales...
September 1, 2016: Nuclear Instruments & Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
https://www.readbyqxmd.com/read/28700203/mechanisms-of-atmospherically-relevant-cluster-growth
#5
Bryan R Bzdek, Joseph W DePalma, Murray V Johnston
Atmospheric aerosols impact global climate either directly by scattering solar radiation or indirectly by serving as cloud condensation nuclei, which influence cloud albedo and precipitation patterns. Our scientific understanding of these impacts is poor relative to that of, for instance, greenhouse gases, in part because it is difficult to predict particle number concentrations. One important pathway by which particles are added to the atmosphere is new particle formation, where gas phase precursors form molecular clusters that subsequently grow to the climatically relevant size range (50-100 nm diameter)...
July 12, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28698372/crystal-structure-of-co-bound-cytochrome-c-oxidase-determined-by-serial-femtosecond-x-ray-crystallography-at-room-temperature
#6
Izumi Ishigami, Nadia A Zatsepin, Masahide Hikita, Chelsie E Conrad, Garrett Nelson, Jesse D Coe, Shibom Basu, Thomas D Grant, Matthew H Seaberg, Raymond G Sierra, Mark S Hunter, Petra Fromme, Raimund Fromme, Syun-Ru Yeh, Denis L Rousseau
Cytochrome c oxidase (CcO), the terminal enzyme in the electron transfer chain, translocates protons across the inner mitochondrial membrane by harnessing the free energy generated by the reduction of oxygen to water. Several redox-coupled proton translocation mechanisms have been proposed, but they lack confirmation, in part from the absence of reliable structural information due to radiation damage artifacts caused by the intense synchrotron radiation. Here we report the room temperature, neutral pH (6.8), damage-free structure of bovine CcO (bCcO) in the carbon monoxide (CO)-bound state at a resolution of 2...
July 11, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28690343/state-to-state-chemistry-and-rotational-excitation-of-ch-in-photon-dominated-regions
#7
A Faure, P Halvick, T Stoecklin, P Honvault, M D Epée Epée, J Zs Mezei, O Motapon, I F Schneider, J Tennyson, O Roncero, N Bulut, A Zanchet
We present a detailed theoretical study of the rotational excitation of CH(+) due to reactive and nonreactive collisions involving C(+)((2)P), H2, CH(+), H and free electrons. Specifically, the formation of CH(+) proceeds through the reaction between C(+)((2)P) and H2(νH2 = 1, 2), while the collisional (de)excitation and destruction of CH(+) is due to collisions with hydrogen atoms and free electrons. State-to-state and initial-state-specific rate coefficients are computed in the kinetic temperature range 10-3000 K for the inelastic, exchange, abstraction and dissociative recombination processes using accurate potential energy surfaces and the best scattering methods...
July 2017: Monthly Notices of the Royal Astronomical Society
https://www.readbyqxmd.com/read/28667308/enhanced-pm2-5-pollution-in-china-due-to-aerosol-cloud-interactions
#8
Bin Zhao, Kuo-Nan Liou, Yu Gu, Qinbin Li, Jonathan H Jiang, Hui Su, Cenlin He, Hsien-Liang R Tseng, Shuxiao Wang, Run Liu, Ling Qi, Wei-Liang Lee, Jiming Hao
Aerosol-cloud interactions (aerosol indirect effects) play an important role in regional meteorological variations, which could further induce feedback on regional air quality. While the impact of aerosol-cloud interactions on meteorology and climate has been extensively studied, their feedback on air quality remains unclear. Using a fully coupled meteorology-chemistry model, we find that increased aerosol loading due to anthropogenic activities in China substantially increases column cloud droplet number concentration and liquid water path (LWP), which further leads to a reduction in the downward shortwave radiation at surface, surface air temperature and planetary boundary layer (PBL) height...
June 30, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28650775/urine-interleukin-18-il-18-as-a-biomarker-of-total-body-irradiation-a-preliminary-study-in-nonhuman-primates
#9
Mang Xiao, David L Bolduc, XiangHong Li, Wanchang Cui, Kevin P Hieber, Rolf Bünger, Natalia I Ossetrova
We have reported that circulating IL-18 can be used as a radiation biomarker in mice, minipigs and nonhuman primates (NHPs, Macaca mulatta). Here, we report the levels of IL-18 in individual NHP's urine before and at 6 h-7 days after 5.0, 6.5 and 8.5 Gy (60)Co total-body irradiation (TBI) using enzyme linked immunosorbent assay (ELISA). Six animals (3.5-5.5 kg, 3-4 years old) per radiation dose were investigated. Correlation values between urine IL-18 and blood cell counts and serum chemistry parameters including lactate dehydrogenase (LDH), lipase, and serum total protein (TP), as well as between urine IL-18 and 60-day survival, were analyzed...
June 26, 2017: Radiation Research
https://www.readbyqxmd.com/read/28631802/aqueous-tantalum-polyoxometalate-reactivity-with-peroxide
#10
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
#11
Linda Feketeová, Bun Chan, George N Khairallah, Vincent Steinmetz, Philippe Maitre, 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 characterize, and examine the reactivity of the Watson-Crick nucleobase pair radical cation in the gas phase...
June 27, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28618830/acoustic-levitation-of-an-object-larger-than-the-acoustic-wavelength
#12
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
#13
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
#14
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
#15
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
#16
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
#17
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
#18
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
#19
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
#20
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
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