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Although reactive oxygen species (ROS)‐mediated tumor treatments are predominant in clinical applications, ROS‐induced protective autophagy promotes cell survival, especially in hypoxic tumors. Herein, X‐ray triggered nitrite (NO2−) is used for hypoxic prostate cancer therapy by inhibiting autophagy and inducing nitrosative stress based on an electrophilic zeolitic imidazole framework (ZIF‐82‐PVP). After internalization of pH‐responsive ZIF‐82‐PVP nanoparticles, electrophilic ligands and Zn2+ are delivered into cancer cells. Electrophilic ligands can not only consume GSH under hypoxia but also capture low‐energy electrons derived from X‐rays to generate NO2−, which inhibits autophagy and further elevates lethal nitrosative stress levels. In addition, dissociated Zn2+ specifically limits the migration and invasion of prostate cancer cells through ion interference. In vitro and in vivo results indicate that ZIF‐82‐PVP nanoparticles under X‐ray irradiation can effectively promote the apoptosis of hypoxic prostate cancer cells. Overall, this nitrosative stress‐mediated tumor therapy strategy provides a novel approach targeting hypoxic tumors. [ABSTRACT FROM AUTHOR]

At geosynchronous Earth orbit, the radiation belt/ring current electron fluxes with energies up to several hundred kiloelectron volts can vary widely in magnetic local time (MLT). This study aims to develop Nonlinear AutoRegressive eXogenous models using system science techniques, which account for the spatial variation in MLT. This is difficult for system science techniques, since there is sparse data availability of the electron fluxes at different MLT. To solve this problem, the data are binned from Geostationary Operational Environmental Satellites (GOES) 13, 14, and 15 by MLT, and a separate Nonlinear AutoRegressive eXogenous model is deduced for each bin using solar wind variables as the inputs to the model. These models are then conjugated into one spatiotemporal forecast. The model performance statistics for each model varies in MLT with a prediction efficiency between 47% and 75% and a correlation coefficient between 51.3% and 78.9% for the period from 1 March 2013 to 31 December 2017. Key Points: This study develops Nonlinear AutoRegressive eXogenous models that account for the spatial variation in MLT of GEO 30‐ to 500‐keV electron fluxesThe model performance varies with MLT having a prediction efficiency between 47% and 75% and a correlation coefficient between 51% and 79%The resulting models show that the IMF has the largest control over the variations in the GEO 30‐ to 50‐keV electron fluxes [ABSTRACT FROM AUTHOR]

The measurement of clustered damages in Pt‐chemotherapeutic‐drugs‐DNA complexes induced by low‐energy (0‐30 eV) electrons (LEEs) may provide further understanding of the synergy mechanism in cancer treatment with concomitant chemoradiation therapy (CRT). Five‐monolayer films of Pt‐DNA complexes, containing cisplatin, carboplatin and oxaliplatin with ratio 5:1 were irradiated with mono‐energetic electrons of 10 eV, the most prominent energy for bond dissociation by LEE impact. Damages to plasmid DNA including crosslinks, SSBs, DSBs and the loss of the supercoiled configuration were analyzed by the electrophoresis. Base damages (BDs) occurring within two turns of DNA helix were detected by the treatment of E. coli base excision repair endonuclease (Nth and Fpg). The total DNA damages to Pt‐DNA complexes was found to be 350 ± 42, 296 ± 45 and 434 ± 46 ×10−15 electron−1molecule−1, respectively, while the percentages of BDs in this total were 56%, 54% and 60%, respectively. Compared to unmodified DNA, binding of Pt‐drugs to DNA increased BDs by factors of 1.9, 1.6 and 2.6, respectively, which partly resulted in significant enhancements of potentially lethal lesions (i. e. crosslinks, double strand breaks (DSBs) and non‐DSB cluster damages). These results reveal the significant role that LEEs play in the formation of clustered DNA damages related to BDs, which are expected to contribute to the higher efficacy of cancer treatment by CRT with the Pt‐drugs investigated. Binding of Pt‐drugs to DNA with electron irradiation at 10 eV significantly lead to enhancements of potentially lethal lesions, including crosslinks, double strand breaks (DSBs) and non‐DSB cluster damages. Base damages contributes the important perspective in the LEEs‐induced clustered DNA damages mechanism, which are expected to benefit the higher efficacy of cancer treatment by CRT with the Pt‐drugs. [ABSTRACT FROM AUTHOR]

Abstract: High‐energy radiation is used in combination with radiosensitizing therapeutics to treat cancer. The most common radiosensitizers are halogenated nucleosides and cisplatin derivatives, and recently also metal nanoparticles have been suggested as potential radiosensitizing agents. The radiosensitizing action of these compounds can at least partly be ascribed to an enhanced reactivity towards secondary low‐energy electrons generated along the radiation track of the high‐energy primary radiation, or to an additional emission of secondary reactive electrons close to the tumor tissue. This is referred to as physico‐chemical radiosensitization. In this Concept article we present current experimental methods used to study fundamental processes of physico‐chemical radiosensitization and discuss the most relevant classes of radiosensitizers. Open questions in the current discussions are identified and future directions outlined, which can lead to optimized treatment protocols or even novel therapeutic concepts. [ABSTRACT FROM AUTHOR]

Abstract: In a recent study, Liang et al. (2017, https://doi.org/10.1002/2017JA024127) repeatedly identified strong electron temperature (Te) enhancements when Swarm satellites traversed pulsating auroral patches. In this study, we use joint optical and Poker Flat Incoherent Scatter Radar (PFISR) observations to further investigate the F region plasma signatures related to pulsating auroras. On 19 March 2015 night, which contained multiple intervals of pulsating auroral activities, we identify a statistical trend, albeit not a one‐to‐one correspondence, of strong Te enhancements (~500–1000 K) in the upper F region ionosphere during the passages of pulsating auroras over PFISR. On the other hand, there is no discernible and repeatable density enhancement in the upper F region during pulsating auroral intervals. Collocated optical and NOAA satellite observations suggest that the pulsating auroras are composed of energetic electron precipitation with characteristic energy >10 keV, which is inefficient in electron heating in the upper F region. Based upon PFISR observations and simulations from Liang et al. (2017) model, we propose that thermal conduction from the topside ionosphere, which is heated by precipitating low‐energy electrons, offers the most likely explanation for the observed electron heating in the upper F region associated with pulsating auroras. Such a heating mechanism is similar to that underlying the “stable auroral red arcs” in the subauroral ionosphere. Our proposal conforms to the notion on the coexistence of an enhanced cold plasma population and the energetic electron precipitation, in magnetospheric flux tubes threading the pulsating auroral patch. In addition, we find a trend of enhanced ion upflows during pulsating auroral intervals. [ABSTRACT FROM AUTHOR]

Low-energy electrons effectively decompose the isomers 2-nitroimidazole and 4(5)-nitroimidazole by dissociative electron attachment (DEA) into a variety of fragment anions and radicals. The present study shows that a distinct selectivity for the two isomers occurs in the DEA reactions. Several new decay channels are observed for 2-nitroimidazole, including a dominant one leading to the loss of molecular H2O by attachment of a low-energy electron. In contrast, the loss of a single hydrogen atom is a much more efficient reaction in DEA to 4(5)-nitroimidazole. Quantum chemical calculations were carried out to explain the pronounced isomer effect found in the DEA experiment. Although the free energies of the reactions are similar for the different isomers, the very different natures of the dipole-bound states and valence-bound anions lead to preference for or hindrance of a particular dissociation channel. Nitroimidazolic compounds are considered as radiosensitizing compounds in tumor radiation therapy. The enhanced formation of fragments, including the highly reactive hydroxyl radical, in DEA to 2-nitroimidazole suggests that it may be a more efficient radiosensitizing agent than 4(5)-nitroimidazoles. [ABSTRACT FROM AUTHOR]

Methylammonium lead iodide perovskite (MAPbI3), a prototype material for potentially high-efficient and low-cost organic-inorganic hybrid perovskite solar cells, has been investigated intensively in recent years. A study of low-energy electron-induced transformations in MAPbI3 is presented, performed by combining controlled electron-impact irradiation with X-ray photoelectron spectroscopy and scanning electron microscopy. Changes were observed in both the elemental composition and the morphology of irradiated MAPbI3 thin films as a function of the electron fluence for incident energies from 4.5 to 60 eV. The results show that low-energy electrons can affect structural and chemical properties of MAPbI3. It is proposed that the transformations are triggered by the interactions with the organic part of the material (methylammonium), resulting in the MAPbI3 decomposition and aggregation of the hydrocarbon layer. [ABSTRACT FROM AUTHOR]

Low-energy electrons (LEEs) at energies of less than 2 eV effectively decompose 4-nitroimidazole (4NI) by dissociative electron attachment (DEA). The reactions include simple bond cleavages but also complex reactions involving multiple bond cleavages and formation of new molecules. Both simple and complex reactions are associated with pronounced sharp features in the anionic yields, which are interpreted as vibrational Feshbach resonances acting as effective doorways for DEA. The remarkably rich chemistry of 4NI is completely blocked in 1-methyl-4-nitroimidazole (Me4NI), that is, upon methylation of 4NI at the N1 site. These remarkable results have also implications for the development of nitroimidazole based radiosensitizers in tumor radiation therapy. [ABSTRACT FROM AUTHOR]

Sugar-base C1′&bond;N1 and phosphate-sugar C5′&bond;O5′ bond breakings of 2′-deoxycytidine-5′-monophosphates (dCMP) and 2′-deoxythymidine-5′- monophosphates (dTMP) and their radical anions have been explored theoretically at the B3LYP/DZP++ level of theory. Calculations show that the low-energy electrons attachment to the pyrimidine nucleotides results in remarkable structural and chemical bonding changes. Predicted Gibbs free energies of reaction ΔG for the C5′&bond;O5′ bond dissociation process of the radical anions are -14.6 and -11.5 kcal mol-1, respectively, and such dissociation processes may be intrinsically spontaneous in the gas phase. Furthermore, the C5′&bond;O5′ bond cleavage processes of the anionic dCMP and dTMP were predicted to have activation energies of 6.9 and 8.0 kcal mol-1 in the gas phase, respectively, much lower than the barriers for the C1′&bond;N1 bond breaking process, showing that the C&bond;O bond dissociation in DNA single strand breaks is a dominant process as observed experimentally. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008 [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted to study the effect of soft electron (low-energy electron) treatment on adzuki bean weevil, Callosobruchus chinensis (L.), a major pest of stored legume seeds. Adzuki bean ( Vigna angularis) seeds containing weevils of different ages (0, 2, 4, 6, 8, 10, 12, 14, 16 and 18 days), were exposed to electrons at an acceleration voltage of 170 kV for 20 min (10 kGy). The radiation sensitivity of the insect decreased with increasing age. The egg stage was highly susceptible to electron radiation whereas the 18-day-old stage (fully developed adults ready for emergence) was the most tolerant, and treatment at a higher energy (200 kV equal to 10 kGy) was necessary to achieve an 80% mortality of this stage. However, the longevity, fecundity and fertility of the surviving adult insects were adversely affected by the electron treatment and they failed to complete their life cycle. The sex ratio of weevils was not significantly affected by the electron treatment, suggesting an equal vulnerability of both sexes. Electron treatment did not affect the germination capacity of adzuki bean seeds, so soft electron irradiation represents a safer method for the disinfestation of adzuki beans. [ABSTRACT FROM AUTHOR]