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1.
Phys Chem Chem Phys ; 26(19): 14440-14447, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38713097

RESUMO

128 organic halide perovskites are systematically investigated using high-throughput first principles calculations where Ge and Sn-based materials are searched. The results revealed that all calculated materials exhibited exothermic reactions. Notably, a correlation between the heat of formation and X-site ions is identified. Six specific compounds, namely FA-Ge-I-I-I, FA-Sn-F-I-I, FA-Sn-Cl-I-I, FA-Sn-Br-Br-I, FA-Sn-Br-I-I, and FA-Sn-I-I-I, where FA stands for formamidinium, are found to have a bandgap ranging from 1.0 to 2.0 eV, characterized by a direct bandgap in their band structure. Electronic structure analysis indicated that the CBM (conduction band minimum) is influenced by the B-site p-orbital, while the VBM (valence band maximum) is influenced by the X-site p-orbitals. This study underscores the capability of high-throughput calculations to unveil hidden trends in perovskite materials, offering an effective approach for the exploration of promising perovskite materials.

2.
Chemphyschem ; 24(13): e202300115, 2023 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-37083307

RESUMO

2 dimensional (2D) dodecagonal boron nitride (D_BN) and graphenylene are being investigated to understand their potential applications in water purification. First principle calculations are performed to evaluate the water purification properties of D_BN and graphenylene. It is found that Na+ exothermically adsorbs on pores in D_BN, where the transition state energy via pores is calculated to be 0.03 eV. This indicates that Na+ can pass through D_BN pores more selectively than water molecules and other ions. In contrast, in the case of graphenylene, Na+ is repelled, and H2 O exothermically adsorbs on pores, where the transition state energy via pores is calculated to be 1.00 eV. Therefore, this demonstrates that D_BN exhibits an excellent potential for ion-sieving membranes, while graphenylene exhibits an excellent potential for reverse osmosis membranes. Consequently, this study provides valuable insights into the potential use of D_BN and graphenylene in water purification applications.

3.
Sensors (Basel) ; 23(4)2023 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-36850923

RESUMO

The rapid proliferation of the emerging yet promising notion of the Internet-of-Vehicles (IoV) has led to the development of a variety of conventional trust assessment schemes to tackle insider attackers. The primary reliance of these frameworks is on the accumulation of individual trust attributes. While aggregating these influential parameters, weights are often associated with each individual attribute to reflect its impact on the final trust score. It is of paramount importance that such weights be precise to lead to an accurate trust assessment. Moreover, the value of the minimum acceptable trust threshold employed for the identification of dishonest vehicles needs to be carefully defined to avoid delayed or erroneous detection. This paper employs an IoT data set from CRAWDAD by suitably transforming it into an IoV format. This data set encompasses information regarding 18,226 interactions among 76 nodes, both honest and dishonest. First, the influencing parameters (i.e., packet delivery ratio, familiarity, timeliness and interaction frequency) were computed, and two feature matrices were formed. The first matrix (FM1) takes into account all the pairwise individual parameters as individual features, whereas the second matrix (FM2) considers the average of all pairwise computations performed for each individual parameter as one feature. Subsequently, unsupervised learning is employed to achieve the ground truth prior to applying supervised machine learning algorithms for classification purposes. It is worth noting that Subspace KNN yielded a perfect precision, recall, and the F1-score equal to 1 for individual parametric scores, whereas Subspace Discriminant returned an ideal precision, recall, and the F1-score equal to 1 for mean parametric scores. It is also evident from extensive simulations that FM2 yielded more accurate classification results compared to FM1. Furthermore, decision boundaries among honest and dishonest vehicles have also been computed for respective feature matrices.

4.
Sensors (Basel) ; 23(5)2023 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-36904951

RESUMO

Quantum machine learning (QML) has attracted significant research attention over the last decade. Multiple models have been developed to demonstrate the practical applications of the quantum properties. In this study, we first demonstrate that the previously proposed quanvolutional neural network (QuanvNN) using a randomly generated quantum circuit improves the image classification accuracy of a fully connected neural network against the Modified National Institute of Standards and Technology (MNIST) dataset and the Canadian Institute for Advanced Research 10 class (CIFAR-10) dataset from 92.0% to 93.0% and from 30.5% to 34.9%, respectively. We then propose a new model referred to as a Neural Network with Quantum Entanglement (NNQE) using a strongly entangled quantum circuit combined with Hadamard gates. The new model further improves the image classification accuracy of MNIST and CIFAR-10 to 93.8% and 36.0%, respectively. Unlike other QML methods, the proposed method does not require optimization of the parameters inside the quantum circuits; hence, it requires only limited use of the quantum circuit. Given the small number of qubits and relatively shallow depth of the proposed quantum circuit, the proposed method is well suited for implementation in noisy intermediate-scale quantum computers. While promising results were obtained by the proposed method when applied to the MNIST and CIFAR-10 datasets, a test against a more complicated German Traffic Sign Recognition Benchmark (GTSRB) dataset degraded the image classification accuracy from 82.2% to 73.4%. The exact causes of the performance improvement and degradation are currently an open question, prompting further research on the understanding and design of suitable quantum circuits for image classification neural networks for colored and complex data.

5.
Ecotoxicol Environ Saf ; 243: 113971, 2022 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-35981482

RESUMO

Anticoagulant rodenticides have been widely used to eliminate wild rodents, which as invasive species on remote islands can disturb ecosystems. Since rodenticides can cause wildlife poisoning, it is necessary to evaluate the sensitivity of local mammals and birds to the poisons to ensure the rodenticides are used effectively. The Bonin Islands are an archipelago located 1000 km southeast of the Japanese mainland and are famous for the unique ecosystems. Here the first-generation anticoagulant rodenticide diphacinone has been used against introduced black rats (Rattus rattus). The only land mammal native to the archipelago is the Bonin fruit bat (Pteropus pselaphon), but little is known regarding its sensitivity to rodenticides. In this study, the Egyptian fruit bats (Rousettus aegyptiacus) was used as a model animal for in vivo pharmacokinetics and pharmacodynamics analysis and in vitro enzyme kinetics using their hepatic microsomal fractions. The structure of vitamin K epoxide reductase (VKORC1), the target protein of the rodenticide in the Bonin fruit bat, was predicted from its genome and its binding affinity to rodenticides was evaluated. The Egyptian fruit bats excreted diphacinone slowly and showed similar sensitivity to rats. In contrast, they excreted warfarin, another first-generation rodenticide, faster than rats and recovered from the toxic effect faster. An in silico binding study also indicated that the VKORC1 of fruit bats is relatively tolerant to warfarin, but binds strongly to diphacinone. These results suggest that even chemicals with the same mode of action display different sensitivities in different species: fruit bat species are relatively resistant to warfarin, but vulnerable to diphacinone.


Assuntos
Quirópteros , Rodenticidas , Animais , Anticoagulantes/toxicidade , Quirópteros/metabolismo , Ecossistema , Mamíferos/metabolismo , Fenindiona/análogos & derivados , Ratos , Rodenticidas/toxicidade , Toxicocinética , Vitamina K Epóxido Redutases/genética , Vitamina K Epóxido Redutases/metabolismo , Varfarina/toxicidade
6.
BMC Med Educ ; 22(1): 202, 2022 Mar 25.
Artigo em Inglês | MEDLINE | ID: mdl-35337317

RESUMO

BACKGROUND: The purpose of this study was to develop an objective, content-valid, and reliable assessment method for Kampo medicine using an objective structured clinical examination (OSCE) for the assessment of clinical competence in Kampo medicine. METHODS: We developed a blueprint followed by a list of 47 assessment items and three task scenarios related to clinical competence in Kampo medicine. An eight-member test committee checked the relevance of the assessment items on a Likert scale. We calculated a content validity index and content validity ratio, and used the Angoff method to set the passing threshold. We trained a total of nine simulated patients with three assigned to each scenario. We conducted an OSCE for 11 candidates with varying medical abilities, and conducted three stations per person, which were evaluated by one evaluator in one room by direct observation. We used video recordings to test the inter-rater reliability of the three raters. We used the test results to verify the reliability of the assessment chart. RESULTS: The inter-rater reliability (intraclass correlation coefficient [2,1]) was 0.973. The reliability of the assessment chart for each scenario (Cronbach's α) was 0.86, 0.89, and 0.85 for Scenarios 1, 2, and 3, respectively. The reliability of the assessment chart for the whole OSCE (Cronbach's α) was 0.90. CONCLUSIONS: We developed a content-valid new OSCE assessment method for Kampo medicine and obtained high inter-rater and test reliabilities. Our findings suggest that this is one of the most reliable evaluation methods for assessing clinical competence in Kampo medicine.


Assuntos
Avaliação Educacional , Medicina Kampo , Competência Clínica , Avaliação Educacional/métodos , Humanos , Exame Físico , Reprodutibilidade dos Testes
7.
Chem Soc Rev ; 50(24): 13692-13729, 2021 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-34842873

RESUMO

Solar energy is attractive because it is free, renewable, abundant and sustainable. Photocatalysis is one of the feasible routes to utilize solar energy for the degradation of pollutants and the production of fuel. Perovskites and their derivatives have received substantial attention in both photocatalytic wastewater treatment and energy production because of their highly tailorable structural and physicochemical properties. This review illustrates the basic principles of photocatalytic reactions and the application of these principles to the design of robust and sustainable perovskite photocatalysts. It details the structures of the perovskites and the physics and chemistry behind photocatalytic reactions and describes the advantages and limitations of popular strategies for the design of photoactive perovskites. This is followed by examples of how these strategies are applied to enhance the photocatalytic efficiency of oxide, halide and oxyhalide perovskites, with a focus on materials with potential for practical application, that is, not containing scarce or toxic elements. It is expected that this overview of the development of photocatalysts and deeper understanding of photocatalytic principles will accelerate the exploitation of efficient perovskite photocatalysts and bring about effective solutions to the energy and environmental crisis.


Assuntos
Compostos de Cálcio , Óxidos , Catálise , Titânio
8.
J Am Chem Soc ; 143(22): 8446-8453, 2021 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-33998815

RESUMO

The development of semiconductors with narrow band gap and high stability is crucial for achieving solar to chemical energy conversion. Compounds with iodine, which has a high polarizability, have attracted attention because of their narrow band gap and long carrier lifetime, as typified by halide perovskite solar cells; however, they have been regarded as unsuitable for harsh photocatalytic water splitting because iodine is prone to self-oxidation. Here, we demonstrate that Ba2Bi3Nb2O11I, a layered Sillén-Aurivillius oxyiodide, not only has access to a wider range of visible light than its chloride and bromide counterparts, but also functions as a stable photocatalyst, efficiently oxidizing water. Density functional theory calculations reveal that the oxygen 2p orbitals in the perovskite block, rather than the fluorite Bi2O2 block as previously pointed out, anomalously push up the valence band maximum, which can be explained by a modified Madelung potential analysis that takes into account the high polarizability of iodine. In addition, the highly polarizable iodide contributes to longer carrier lifetime of Ba2Bi3Nb2O11I, allowing for a significantly higher quantum efficiency than its chloride and bromide counterparts. Visible-light-driven Z-scheme water splitting was achieved for the first time in an iodine-based system using Ba2Bi3Nb2O11I as an oxygen-evolution photocatalyst. The present study provides a novel approach for incorporating polarizable "soft" anions into building blocks of layered materials to manipulate the band structure and improve the carrier dynamics for visible-light responsive functions.

9.
J Am Chem Soc ; 143(6): 2491-2499, 2021 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-33417448

RESUMO

The discovery of building blocks offers new opportunities to develop and control properties of extended solids. Compounds with fluorite-type Bi2O2 blocks host various properties including lead-free ferroelectrics and photocatalysts. In this study, we show that triple-layered Bi2MO4 blocks (M = Bi, La, Y) in Bi2MO4Cl allow, unlike double-layered Bi2O2 blocks, to extensively control the conduction band. Depending on M, the Bi2MO4 block is truncated by Bi-O bond breaking, resulting in a series of n-zigzag chain structures (n = 1, 2, ∞ for M = Bi, La, Y, respectively). Thus, formed chain structures are responsible for the variation in the conduction band minimum (-0.36 to -0.94 V vs SHE), which is correlated to the presence or absence of mirror symmetry at Bi. Bi2YO4Cl shows higher photoconductivity than the most efficient Bi2O2-based photocatalyst with promising visible-light photocatalytic activity for water splitting. This study expands the possibilities of thickening (2D to 3D) and cutting (2D to 1D) fluorite-based blocks toward desired photocatalysis and other functions.

10.
J Neuroinflammation ; 18(1): 227, 2021 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-34645458

RESUMO

BACKGROUND: Macrophages in the peripheral nervous system are key players in the repair of nerve tissue and the development of neuropathic pain due to peripheral nerve injury. However, there is a lack of information on the origin and morphological features of macrophages in sensory ganglia after peripheral nerve injury, unlike those in the brain and spinal cord. We analyzed the origin and morphological features of sensory ganglionic macrophages after nerve ligation or transection using wild-type mice and mice with bone-marrow cell transplants. METHODS: After protecting the head of C57BL/6J mice with lead caps, they were irradiated and transplanted with bone-marrow-derived cells from GFP transgenic mice. The infraorbital nerve of a branch of the trigeminal nerve of wild-type mice was ligated or the infraorbital nerve of GFP-positive bone-marrow-cell-transplanted mice was transected. After immunostaining the trigeminal ganglion, the structures of the ganglionic macrophages, neurons, and satellite glial cells were analyzed using two-dimensional or three-dimensional images. RESULTS: The number of damaged neurons in the trigeminal ganglion increased from day 1 after infraorbital nerve ligation. Ganglionic macrophages proliferated from days 3 to 5. Furthermore, the numbers of macrophages increased from days 3 to 15. Bone-marrow-derived macrophages increased on day 7 after the infraorbital nerve was transected in the trigeminal ganglion of GFP-positive bone-marrow-cell-transplanted mice but most of the ganglionic macrophages were composed of tissue-resident cells. On day 7 after infraorbital nerve ligation, ganglionic macrophages increased in volume, extended their processes between the neurons and satellite glial cells, and contacted these neurons. Most of the ganglionic macrophages showed an M2 phenotype when contact was observed, and little neuronal cell death occurred. CONCLUSION: Most of the macrophages that appear after a nerve injury are tissue-resident, and these make direct contact with damaged neurons that act in a tissue-protective manner in the M2 phenotype. These results imply that tissue-resident macrophages signal to neurons directly through physical contact.


Assuntos
Transplante de Medula Óssea/métodos , Crescimento Celular , Gânglios Sensitivos/patologia , Macrófagos/patologia , Traumatismos dos Nervos Periféricos/patologia , Células Receptoras Sensoriais/patologia , Animais , Gânglios Sensitivos/imunologia , Macrófagos/imunologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Traumatismos dos Nervos Periféricos/imunologia , Traumatismos dos Nervos Periféricos/terapia , Células Receptoras Sensoriais/imunologia
11.
Inorg Chem ; 60(20): 15667-15674, 2021 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-34596398

RESUMO

Layered oxyhalides containing double or triple fluorite layers are promising visible-light-responsive water-splitting photocatalysts with unique band structures. Herein, we report on the synthesis, structure, and photocatalytic property of Bi4BaO6Cl2 (I4/mmm) with alternating double (Bi2O2) and triple (Bi2BaO4) fluorite layers, which was extracted from the crystallographic database on the basis of Madelung potential calculations. Rietveld refinements from powder X-ray and neutron diffraction data revealed the presence of cationic disorder between Bi2O2 and Bi2BaO4 layers, leading to electrostatic stabilization. DFT calculations suggested that photogenerated electrons and holes flow through the double and triple layers, respectively, which may suppress electron-hole recombination. We expanded this double-triple system to include Bi4CaO6Cl2 and Bi4SrO6Cl2 with orthorhombic distortions and different degrees of cationic disorder, which allow band gap tuning. All the double-triple compounds Bi4AO6Cl2 showed stable water-splitting photocatalysis in the presence of a sacrificial reagent.

12.
J Am Chem Soc ; 142(21): 9752-9762, 2020 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-32352795

RESUMO

Visible-light-driven hydrogen (H2) production from water is a promising strategy to convert and store solar energy as chemical energy. Covalent organic frameworks (COFs) are front runners among different classes of organic photocatalysts. The photocatalytic activity of COFs depends on numerous factors such as the electronic band gap, crystallinity, surface area, exciton migration, stability of transient species, charge separation and transport, etc. However, it is challenging to fine tune all of these factors simultaneously to enhance the photocatalytic activity. Hence, in this report, an effort has been made to understand the interplay of these factors and identify the key factors for efficient photocatalytic H2 production through a structure-property-activity relationship. Careful molecular engineering allowed us to optimize all of the above plausible factors impacting the overall catalytic activities of a series of isoreticular COFs. The present study determines three prime factors: light absorption, charge carrier generation, and its transport, which influence the photocatalytic H2 production of COFs to a much greater extent than the other factors.

13.
Chem Rev ; 118(10): 5201-5241, 2018 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-29676566

RESUMO

Visible light-driven water splitting using cheap and robust photocatalysts is one of the most exciting ways to produce clean and renewable energy for future generations. Cutting edge research within the field focuses on so-called "Z-scheme" systems, which are inspired by the photosystem II-photosystem I (PSII/PSI) coupling from natural photosynthesis. A Z-scheme system comprises two photocatalysts and generates two sets of charge carriers, splitting water into its constituent parts, hydrogen and oxygen, at separate locations. This is not only more efficient than using a single photocatalyst, but practically it could also be safer. Researchers within the field are constantly aiming to bring systems toward industrial level efficiencies by maximizing light absorption of the materials, engineering more stable redox couples, and also searching for new hydrogen and oxygen evolution cocatalysts. This review provides an in-depth survey of relevant Z-schemes from past to present, with particular focus on mechanistic breakthroughs, and highlights current state of the art systems which are at the forefront of the field.

14.
Parasitology ; 147(14): 1765-1773, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32943118

RESUMO

The duognathous haemadipsid leeches of the genus Chtonobdella show a trans-oceanic distribution throughout the Indo-Pacific region. Although passive long-distance dispersal (LDD) of Chtonobdella leeches by birds has been suggested, little is known about the host-parasite relationships between avian hosts and Chtonobdella leeches. In the current study, we investigated Chtonobdella leech infestations of the eyes and other mucus membranes of migratory procellariiform seabirds, Pterodroma hypoleuca and Oceanodroma tristrami, captured at six locations in the Bonin Islands, Honshu and Okinawa Island, Japan. Analyses of the partial sequences of 18S rRNA, 28S rRNA, and mitochondrial cytochrome c oxidase subunit I (COI) and morphological examination of the specimens demonstrated that the Chtonobdella leeches belonged to Chtonobdella palmyrae, which is indigenous to Palmyra Atoll in the Northern Line Islands. A dominant COI sequence type was observed in samples from all six sites; therefore, C. palmyrae almost surely dispersed approximately 1000 km by infesting the eyes and mucus membranes of procellariiform seabirds. The host-parasite relationships between procellariiform seabirds and C. palmyrae provide explicit evidence of the LDD of duognathous haemadipsid leeches. The taxonomic status of Haemadipsa zeylanica ivosimae from the Volcano Islands is also briefly discussed.


Assuntos
Aves , Helmintíase Animal/parasitologia , Interações Hospedeiro-Parasita , Sanguessugas/fisiologia , Animais , Ilhas , Japão
15.
BMC Bioinformatics ; 19(Suppl 1): 45, 2018 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-29504909

RESUMO

BACKGROUND: The read length of single-molecule DNA sequencers is reaching 1 Mb. Popular alignment software tools widely used for analyzing such long reads often take advantage of single-instruction multiple-data (SIMD) operations to accelerate calculation of dynamic programming (DP) matrices in the Smith-Waterman-Gotoh (SWG) algorithm with a fixed alignment start position at the origin. Nonetheless, 16-bit or 32-bit integers are necessary for storing the values in a DP matrix when sequences to be aligned are long; this situation hampers the use of the full SIMD width of modern processors. RESULTS: We proposed a faster semi-global alignment algorithm, "difference recurrence relations," that runs more rapidly than the state-of-the-art algorithm by a factor of 2.1. Instead of calculating and storing all the values in a DP matrix directly, our algorithm computes and stores mainly the differences between the values of adjacent cells in the matrix. Although the SWG algorithm and our algorithm can output exactly the same result, our algorithm mainly involves 8-bit integer operations, enabling us to exploit the full width of SIMD operations (e.g., 32) on modern processors. We also developed a library, libgaba, so that developers can easily integrate our algorithm into alignment programs. CONCLUSIONS: Our novel algorithm and optimized library implementation will facilitate accelerating nucleotide long-read analysis algorithms that use pairwise alignment stages. The library is implemented in the C programming language and available at https://github.com/ocxtal/libgaba .


Assuntos
Algoritmos , Alinhamento de Sequência/métodos , Análise de Sequência de DNA/métodos , Humanos , Software
16.
Genes Cells ; 22(5): 424-435, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28326644

RESUMO

We developed transgenic (Tg) rats that express human CD4, CCR5, CXCR4, CyclinT1, and CRM1 genes. Tg rat macrophages were efficiently infected with HIV-1 and supported production of infectious progeny virus. By contrast, both rat primary CD4+ T cells and established T cell lines expressing human CD4, CCR5, CyclinT1, and CRM1 genes were infected inefficiently, but this was ameliorated by inhibition of cyclophilin A. The infectivity of rat T cell-derived virus was lower than that of human T cell-derived virus.


Assuntos
Linfócitos T CD4-Positivos/imunologia , Ciclina T/metabolismo , Infecções por HIV/imunologia , Carioferinas/metabolismo , Macrófagos/imunologia , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Linfócitos T CD4-Positivos/virologia , Linhagem Celular , Células Cultivadas , Ciclina T/genética , Suscetibilidade a Doenças , HIV-1/patogenicidade , Humanos , Carioferinas/genética , Macrófagos/virologia , Ratos , Receptores CXCR4/genética , Receptores CXCR4/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Proteína Exportina 1
17.
J Am Chem Soc ; 139(51): 18725-18731, 2017 12 27.
Artigo em Inglês | MEDLINE | ID: mdl-29210576

RESUMO

A layered oxychloride Bi4NbO8Cl is a visible-light responsive catalyst for water splitting, with its remarkable stability ascribed to the highly dispersive O-2p orbitals in the valence band, the origin of which, however, remains unclear. Here, we systematically investigate four series of layered bismuth oxyhalides, BiOX (X = Cl, Br, I), Bi4NbO8X (X = Cl, Br), Bi2GdO4X (X = Cl, Br), and SrBiO2X (X = Cl, Br, I), and found that Madelung site potentials of anions capture essential features of the valence band structures of these materials. The oxide anion in fluorite-like blocks (e.g., [Bi2O2] slab in Bi4NbO8Cl) is responsible for the upward shift of the valence band, and the degree of electrostatic destabilization changes depending on building layers and their stacking sequence. This study suggests that the Madelung analysis enables a prediction and design of the valence band structures of bismuth and other layered oxyhalides and is applicable even to a compound where DFT calculation is difficult to perform.

18.
Appl Microbiol Biotechnol ; 101(2): 659-671, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27766356

RESUMO

We aimed to develop the bioassays for genotixicity and/or oxidative damage using the recombinant yeast. A genotoxicity assay was developed using recombinant Saccharomyces cerevisiae strain BY4741 with a green fluorescent protein (GFP) reporter plasmid, driven by the DNA damage-responsive RNR3 promoter. Enhanced fluorescence induction was observed in DNA repair-deficient strains treated with methyl methanesulfonate, but not with hydrogen peroxide. A GFP reporter yeast strain driven by the oxidative stress-responsive TRX2 promoter was newly developed to assess oxidative damage, but fluorescence was poorly induced by oxidants. In place of GFP, yeast strains with luciferase gene reporter plasmids (luc2 and luc2CP, encoding stable and unstable luciferase, respectively) were prepared. Transient induction of luciferase activity was clearly detected only in a TRX2 promoter-driven luc2CP reporter strain within 90 min of oxidant exposure. However, luciferase was strongly induced by hydroxyurea in the RNR3 promoter-driven luc2 and GFP reporter strains over 8 h after the exposure, suggesting that the RNR3 promoter is continuously upregulated by DNA damage, whereas the TRX2 promoter is transiently activated by oxidative agents. Luciferase activity levels were also increased in a TRX2-promoter-driven luc2CP reporter strain treated with tert-butyl hydroperoxide and menadione and weakly induced with diamide and diethyl maleate. Weakly enhanced luciferase activity induction was detected in the sod1Δ, sod2Δ, and rad27Δ strains treated with hydrogen peroxide compared with that in the wild-type strain. In conclusion, tests using GFP and stable luciferase reporters are useful for genotoxicity, and oxidative damage can be clearly detected by assay with an unstable luciferase reporter.


Assuntos
Genes Reporter , Proteínas de Fluorescência Verde/análise , Luciferases/análise , Mutagênicos/metabolismo , Oxidantes/metabolismo , Estresse Oxidativo , Saccharomyces cerevisiae/efeitos dos fármacos , Proteínas de Fluorescência Verde/genética , Luciferases/genética , Testes de Mutagenicidade/métodos , Regiões Promotoras Genéticas , Saccharomyces cerevisiae/genética , Fatores de Tempo , Ativação Transcricional
19.
J Am Chem Soc ; 138(7): 2082-5, 2016 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-26878489

RESUMO

Mixed anion compounds are expected to be a photocatalyst for visible light-induced water splitting, but the available materials have been almost limited to oxynitrides. Here, we show that an oxychrolide Bi4NbO8Cl, a single layer Sillen-Aurivillius perovskite, is a stable and efficient O2-evolving photocatalyst under visible light, enabling a Z-scheme overall water splitting by coupling with a H2-evolving photocatalyst (Rh-doped SrTiO3). It is found that the valence band maximum of Bi4NbO8Cl is unusually high owing to highly dispersive O-2p orbitals (not Cl-3p orbitals), affording the narrow band gap and possibly the stability against water oxidation. This study suggests that a family of Sillen-Aurivillius perovskite oxyhalides is a promising system to allow a versatile band level tuning for establishing efficient and stable water-splitting under visible light.

20.
J Am Chem Soc ; 137(48): 15315-21, 2015 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-26575595

RESUMO

In synthesizing mixed anion oxides, direct syntheses have often been employed, usually involving high temperature and occasionally high pressure. Compared with these methods, here we show how the use of a titanium perovskite oxyhydride (BaTiO2.5H0.5) as a starting material enables new multistep low temperature topochemical routes to access mixed anion compounds. Similar to labile ligands in inorganic complexes, the lability of H(-) provides the necessary reactivity for syntheses, leading to reactions and products previously difficult to obtain. For example, BaTiO2.5N0.2 can be prepared with the otherwise inert N2 gas at 400-600 °C, in marked contrast with currently available oxynitride synthetic routes. F(-)/H(-) exchange can also be accomplished at 150 °C, yielding the oxyhydride-fluoride BaTi(O, H, F)3. For BaTiO2.4D0.3F0.3, we find evidence that further anionic exchange with OD(-) yields BaTiO2.4(D(-))0.26(OD(-))0.34, which implies stable coexistence of H(+) and H(-) at ambient conditions. Such an arrangement is thermodynamically unstable and would be difficult to realize otherwise. These results show that the labile nature of hydride imparts reactivity to oxide hosts, enabling it to participate in new multistep reactions and form new materials.

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