Search

In the ecological environment, oxytetracycline hydrochloride accumulates seriously and the main source is the discharge of mariculture wastewater. Bismuth oxide was found to do well in removing oxy...

Two-dimensional (2D) Van der Waals ferromagnets carry the promise of ultimately miniature spintronics and information storage devices. Among the newly discovered 2D ferromagnets all inherit the magnetic ordering from their bulk ancestors. Here we report a new 2D ferromagnetic semiconductor at room temperature, 2H phase vanadium diselenide (VSe2) which show ferromagnetic at 2D form only. This unique 2D ferromagnetic semiconductor manifests an enhanced magnetic ordering owing to structural anisotropy at 2D limit.

New method was developed to analyze Pu and Am sequentially for soil and sediment by inductively coupled plasma mass spectrometry (ICPMS). The developed method uses conc. HNO3 to leach Pu and Am, Fe(OH)3 coprecipitation to remove alkali and alkaline metals, extraction chromatographic separation using UTEVA, DGA and TEVA resins to remove interfering elements (IEs) and separate Pu and Am from each other, and sector field-ICPMS to measure Pu and Am. The analysis of four standard reference materials showed that both Pu isotopes and 241Am were accurately determined by this method, as a result of its excellent decontamination ability of IEs. Especially the high decontamination factor of Pu [DF(Pu), 4.2 × 102] in Am fraction and high DF(Am) (7.0 × 103) in Pu fraction sufficiently eliminated the cross interference between 241Pu and 241Am in ICPMS measurement. In addition, stable and high chemical recoveries were achieved for Pu (71–91%) and Am (70–88%). The low LODs of Pu isotopes, short analytical time (14 h) and high DFs of IEs allows this method to sequentially analyze Pu and Am, for both global fallout and nuclear accident sourced samples.

CuO/Bi2O3 photocatalysts were successfully prepared by coprecipitation. The morphology of CuO was like seedlings, growing on the surface of Bi2O3 and forming nanoparticles with enhanced surface pro...

Vanadium diselenide (VSe2), a member of the transition metal dichalcogenides (TMDs) family, is emerging as a promising two-dimensional (2D) candidate for the electronic and spintronic device with e...

Dietary and environmental exposure to titanium dioxide nanoparticles (TiO2 NPs) can cause low-dose and long-term oral exposure in the population, posing a potential adverse health risk. Oxidative stress is considered to be the primary effect of TiO2 NPs through biological interaction. In the present study, we conducted an animal experiment to investigate the element distribution and oxidative stress in Sprague-Dawley rats after oral exposure to TiO2 NPs at daily doses of 0, 2, 10, and 50 mg kg-1 for 90 days. Through the detection of Ti element content in various tissues, limited absorption and distribution of TiO2 NPs in rats was found. However, orally ingested TiO2 NPs still induced tissue-specific oxidative stress and imbalance of elements. Liver tissue was the most sensitive tissue to TiO2 NP-induced oxidative stress, showing decreased reduced glutathione (GSH), increased oxidized glutathione (GSSG) and decreased ratio of GSH/GSSG as well as accumulation of lipid peroxidation (malondialdehyde, MDA) in liver tissues of rats after TiO2 NP exposure (10 and 50 mg kg-1). Meanwhile, oral exposure to TiO2 NPs caused a significant reduction in metal elements such as Mg, Ca and Co in various tissues. Through bioinformatics analysis, the tissue specificity and correlation between the imbalance of elements and oxidative stress were statistically confirmed, but it was difficult to understand the causal relationship. Disorder of element distribution and oxidative stress may lead to a series of subsequent adverse health effects and the tissue specificity would partly explain the target effects of TiO2 NPs.

Based on our previous studies, we show that the M gene is critical for the replication and pathogenicity of the chimeric H17 bat influenza virus (Bat09:mH1mN1) by replacing the bat M gene with those from human and swine influenza A viruses. However, the key amino acids of the M1 and/or M2 proteins that are responsible for virus replication and pathogenicity remain unknown. In this study, replacement of the PR8 M gene with the Eurasian avian-like M gene from the A/California/04/2009 pandemic H1N1 virus significantly decreased viral replication in both mammalian and avian cells in the background of the chimeric H17 bat influenza virus. Further studies revealed that M1 was more crucial for viral growth and pathogenicity than M2 and that the amino acid residues M1-41V and M2-27A were responsible for these characteristics in cells and in mice. These key residues of the M1 and M2 proteins identified in this study might be important for influenza virus surveillance and could be used to produce live attenuated vaccines in the future. IMPORTANCE The M1 and M2 proteins influence the morphology, replication, virulence, and transmissibility of influenza viruses. Although a few key residues in the M1 and M2 proteins have been identified, whether other residues of the M1 and M2 proteins are involved in viral replication and pathogenicity remains to be discovered. In the background of the chimeric H17 bat influenza virus, the Eurasian avian-like M gene from the A/California/04/2009 virus significantly decreased viral growth in mammalian and avian cells. Further study showed that M1 was implicated more than M2 in viral growth and pathogenicity in vitro and in vivo and that the key amino acid residues M1-41V and M2-27A were responsible for these characteristics in cells and in mice. These key residues of the M1 and M2 proteins could be used for influenza virus surveillance and live attenuated vaccine applications in the future. These findings provide important contributions to knowledge of the genetic basis of the virulence of influenza viruses.

LD pumped erbium glass passively Q-switched 1.5μm microchip laser is a research hotspot in laser ranging and imaging application. The high repetition rate microchip laser has serious thermal effect problem, so it is difficult to work stably for a long time. This paper reports a passively Q-switched 1535nm laser with erbium-ytterbium co-doped phosphate glass using double-ended adhesive-free bonding technology. The laser combines YAG crystal, Er3+/Yb3+: glass and Co2+[/sup : MgAl2O4 by bonding to improve the thermal effect of the laser. At the same time, by optimizing the size of the pump light spot, the initial transmittance T0 of the saturable absorber and the reflectivity R of the output mirror, the utilization efficiency of the pump light is improved and the influence of thermal effect is further reduced. The results show that the laser output with the repetition rate of 1kHz, the single pulse energy of 40μJ, pulse width of 8ns, peak power of 5kW, beam quality of 1.4, can output stably for a long time.

The extensive use of antibiotics worldwide has led to phytotoxicity and high risks to humans. Although research on the physiological toxicity of antibiotics is extensive, its influence on plant nitrogen uptake and assimilation remains unclear. The effect of enrofloxacin on nitrogen transformation and assimilation in rice (Oryza sativa L.) seedlings was investigated in this study. Enrofloxacin had no significant effect on rice growth, nitrogen assimilation and metabolism at low concentration, while significant changes were observed in high concentration. The growth of rice seedlings was inhibited, nitrate uptake was enhanced and nitrogen content increased significantly in both shoots and roots in enrofloxacin (800 μg L−1) treatment. Furthermore, enrofloxacin promoted the activity of enzymes related to nitrogen assimilation, including nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase. High enzyme activity resulted in an increase in intermediate products and protein content, suggesting that rice seedlings may detoxify enrofloxacin stress through amino acid binding and nitro-oxidative stress might be one of the reasons of phenotype change. Gas chromatography-mass spectrometry results revealed that different types of metabolites in both shoots and roots increased with enrofloxacin stress. Specifically, glycine, serine, and threonine metabolism; aminoacyl-tRNA biosynthesis; alanine, aspartate, and glutamate metabolism; butanoate metabolism; glyoxylate and dicarboxylate metabolism in shoot; and tyrosine metabolism and citrate cycle in root were affected. Moreover, a significant correlation between nitrogen content, nitrogen assimilation enzyme activity, and metabolite content was observed. Collectively, these findings reveal the potential risks of using reclaimed wastewater irrigation and/or antibiotic-containing animal fertilizers on crops.

Previous studies have shown that chimeric bat influenza viruses can be generated by reverse genetic system. However, the roles of the surface or internal genes of chimeric bat influenza viruses in viral replication and virulence in different host species were still not completely understood. In this study, we generated a chimeric H9N2 bat virus with both HA and NA surface genes from the avian A2093/H9N2 virus and compared its replication and virulence with the chimeric H1N1 bat virus with both HA and NA from the PR8/H1N1 virus in vitro and in mice. The chimeric H1N1 virus showed significantly higher replication in mammalian and avian cells and significantly higher virulence in mice than the chimeric H9N2 virus. Moreover, the chimeric H9N2 virus with the bat influenza internal M gene showed a higher replication in mammalian cells than in avian cells. While the chimeric H9N2 virus with the avian-origin viral M gene displayed a higher replication than that with the bat influenza M gene in avian cells, which likely resulted from increased receptor binding ability to α 2,3 sialic acid linked glycans of the former virus. Our study indicates that bat influenza internal genes are permissive in both mammalian and avian cells, and the bat influenza internal M gene shows more compatibility in mammals than in the avian host. Although the surface genes play more critical roles for viral replication in different host substrates, influenza M gene also potentially impacts on replication, virulence and host tropism.

Neuraminidase (NA) has multiple functions in the life cycle of influenza virus, especially in the late stage of virus replication. Both of hemagglutinin (HA) and NA are highly glycosylated proteins. N-linked glycosylation (NLG) of HA has been reported to contribute to immune escape and virulence of influenza viruses. However, the function of NLG of NA remains largely unclear. In this study, we found that NLG is critical for budding ability of NA. Tunicamycin treatment or NLG knockout significantly inhibited the budding of NA. Further studies showed that the NLG knockout caused attenuation of virus in vitro and in vivo. Notably, the NLG at 219 position plays an important role in the budding, replication, and virulence of H1N1 influenza virus. To explore the underlying mechanism, the unfolded protein response (UPR) was determined in NLG knockout NA overexpressed cells, which showed that the mutant NA was mainly located in the endoplasmic reticulum (ER), the UPR markers BIP and p-eIF2α were upregulated, and XBP1 was downregulated. All the results indicated that NLG knockout NA was stacked in the ER and triggered UPR, which might shut down the budding process of NA. Overall, the study shed light on the function of NLG of NA in virus replication and budding. IMPORTANCE NA is a highly glycosylated protein. Nevertheless, how the NLG affects the function of NA protein remains largely unclear. In this study, we found that NLG plays important roles in budding and Neuraminidase activity of NA protein. Loss of NLG attenuated viral budding and replication. In particular, the 219 NLG site mutation significantly attenuated the replication and virulence of H1N1 influenza virus in vitro and in vivo, which suggested that NLG of NA protein is a novel virulence marker for influenza viruses.

H9N2 avian influenza virus (AIV) has an extended host range, but the molecular basis underlying H9N2 AIV transmission to mammals remains unclear. We isolated more than 900 H9N2 AIVs in our 3-year surveillance in live bird markets in China from 2009 to 2012. Thirty-seven representative isolates were selected for further detailed characterization. These isolates were categorized into 8 genotypes (B64 to B71) and formed a distinct antigenic subgroup. Three isolates belonging to genotype B69, which is a predominant genotype circulating in China, replicated efficiently in mice, while the viruses tested in parallel in other genotypes replicated poorly, although they, like the three B69 isolates, have a leucine at position 226 in the hemagglutinin (HA) receptor binding site, which is critical for binding human type sialic acid receptors. Further molecular and single mutation analysis revealed that a valine (V) residue at position 190 in HA is responsible for efficient replication of these H9N2 viruses in mice. The 190V in HA does not affect virus receptor binding specificity but enhances binding affinity to human cells and lung tissues from mouse and humans. All these data indicate that the 190V in HA is one of the important determinants for H9N2 AIVs to cross the species barrier to infect mammals despite multiple genes conferring adaptation and replication of H9N2 viruses in mammals. Our findings provide novel insights on understanding host range expansion of H9N2 AIVs. IMPORTANCE Influenza virus hemagglutinin (HA) is responsible for binding to host cell receptors and therefore influences the viral host range and pathogenicity in different species. We showed that the H9N2 avian influenza viruses harboring 190V in the HA exhibit enhanced virus replication in mice. Further studies demonstrate that 190V in the HA does not change virus receptor binding specificity but enhances virus binding affinity of the H9N2 virus to human cells and attachment to lung tissues from humans and mouse. Our findings suggest that more attention should be given to the H9N2 AIVs with HA-190V during surveillance due to their potential threat to mammals, including humans.

Employing water splitting as a practicable technique for alternative clean energy requires the development of efficient oxygen evolution electrocatalysts based on inexpensive and earth-abundant materials. Transition metal phosphides have been regarded as promising candidates due to their high electrochemical activity, high conductivity and widespread abundance. However, currently, the oxygen evolution capability of the transition metal phosphides is still limited. It can be noted that the surface state of the electrocatalysts also plays a crucial role in determining the electrocatalytic reaction. In this study, we demonstrate a surface modification strategy using oxygen incorporation in the metallic Ni2P nanosheets catalyst for the first time, leading to dramatically enhanced oxygen evolution activity. The oxygen-incorporated Ni2P nanosheets were achieved through a simple low-temperature phosphidation from the Ni(OH)2 nanosheets precursor. We found that the oxygen incorporation in the Ni2P nanosheets could actively promote the electrochemical performance and presented stable current density of 10 mA cm−2 at a small overpotential of 347 mV with a Tafel slope as low as 63 mV dec−1. Furthermore, the large electrocatalytic current is about 25 times enhanced compared with the pure Ni2P counterpart. Moreover, the high OER performance is superior to most of the reported pure metal phosphide electrocatalysts. These findings point to new opportunities for surface modification to manipulate and improve the reaction of electrocatalysts for designing high performance electrocatalysts and for the investigation of the underlying mechanism of the electrochemical reaction.

We synthesized three kinds of naphthalene tetracarboxylic diimides (NDIs) containing halogenated phenyl groups by one-step reaction, and they were used as organic semiconductor layers in top-contact Organic field-effect transistors (OFETs). Besides, we adopted SiO2/Si substrates that treated by N-octadecylphosphonic acid (ODPA). In addition, a layer of 4, 4′, 4″-triphenylamine (n-3-methylphenyl-n-phenylamine) triphenylamine (m-MTDATA) was deposited by vacuum between the organic semiconductor layer and the gold electrode as the modification material. It was found through experiments that all the organic materials synthesized by us showed n-type organic semiconductor characteristics. Happily, the device made of NDI-FAN attained the highest electron mobility of 2.2 × 10−1 cm2v−1s−1 at room temperature and in air. The crystallinity and morphology of the films were characterized by x-ray diffraction (XRD) and atomic force microscope (AFM). The results expose that introducing electron withdrawing substituents into naphthalene tetracarboxylic diimides besides inserting ODPA and m-MTDATA are effective ways to achieve high electron mobility.

Superconductivity is mutually exclusive with ferromagnetism, because the ferromagnetic exchange field is often destructive to superconducting pairing correlation. Well-designed chemical and physical methods have been devoted to realize their coexistence only by structural integrity of inherent superconducting and ferromagnetic ingredients. However, such coexistence in freestanding structure with nonsuperconducting and nonferromagnetic components still remains a great challenge up to now. Here, we demonstrate a molecule-confined engineering in two-dimensional organic–inorganic superlattice using a chemical building-block approach, successfully realizing first freestanding coexistence of superconductivity and ferromagnetism originated from electronic interactions of nonsuperconducting and nonferromagnetic building blocks. We unravel totally different electronic behavior of molecules depending on spatial confinement: flatly lying Co(Cp)2 molecules in strongly confined SnSe2 interlayers weaken the coordinatio...

For two-dimensional transition metal dichalcogenides (TMD) materials, achieving large size with high quality to provide a basis for the next generation of electronic device geometries has been a long-term need. Here, we demonstrate that, by only manual shaking within several seconds, very large-sized TMD monolayers that cover a wide range of group IVB-VIB transition metal sulfides and selenides can be efficiently harvested from intercalated single-crystal counterparts. Taking TaS2 as examples, monolayers up to unprecedented size (>100 μm) are obtained while maintaining high crystalline quality and the phase structure of the starting materials. Furthermore, benefiting from the gentle manual shaking, we unraveled the atomic-level correlation between the intercalated lattice-strain effects and exfoliated nanosheets, and that strong tensile strain usually led to very large sizes. This work helps to deepen the understanding of exfoliation mechanism and provides a powerful tool for producing large-sized and hig...

We report a photochemical synthesis of Pd/CeO2 catalysts with atomically dispersed Pd. Compared to atomically dispersed Pd/CeO2 with a cubic CeO2 support (Pd/CeO2-CP), atomically dispersed Pd/CeO2 with a truncated octahedral CeO2 support (Pd/CeO2-TOP) exhibited higher activity and selectivity, owing to the synergy between Pd atoms and the (111) surface of CeO2. When compared to Pd/CeO2 with Pd clusters and nanoparticles via chemical reduction, Pd/CeO2-TOP showed excellent activity with an enhancement factor of 324 in CO oxidation, as well as an activity enhancement by a factor of 344 in selective oxidation of benzyl alcohol.

Fe/SiO2 particles with core/shell structure were prepared by coating silica on the surface of a commercial spherical carbonyl iron via the hydrolysis process of tetraethyl orthosilicate (TEOS). The electromagnetic performance of commercial carbonyl iron and as-prepared Fe/SiO2 particles was studied theoretically and experimentally. As predicted by the theoretical calculation based on the Bruggeman formula and the Landau–Lifshitz–Gilbert (LLG) theory, the insulating surface layer of silica was effective to reduce the permittivity parameters of pure carbonyl iron. The measured results showed good agreement with the theoretical prediction. Although there was a little decrease in the permeability of the Fe/SiO2 core/shell particles, a better impedance match especially at higher frequency range was obtained when used as a microwave absorber. The reflection loss (RL) curves show that the lowest reflection loss of Fe/Epoxy composite (−20.5 GHz) was obtained corresponding to the frequency of 8.5 GHz when the thickness of the absorber was 3 mm. A different trend was observed in Fe/SiO2/Epoxy composite. The reflection loss value got lower by decreasing the thickness of absorbers. At the thickness of 2.2 mm, a relative low reflection loss (−17 GHz) corresponding to the frequency of 13.6 GHz was obtained. Compared with the Fe/Epoxy composite, the improvement on shifting the reflection loss peak to higher frequency and on reducing the optimal thickness of absorbers was made by Fe/SiO2/Epoxy composite.

Infrared (IR) harvesting and detection in red and near-IR (NIR) part of the solar spectrum have always been a long-term research area of intense interest. However, limited choices of current photoactive materials have significantly hampered the realization of ultrahigh IR sensitivity under room temperature conditions. The trigger for this requires the exploration of new photo­active materials and the ability to fabricate new photoactive structural design. Herein, a new oxide-catalogue photoconductive NIR detector with ultrahigh performance built by core/shell nanobeam heterostructures (CSNHs) with the inner single-domain monoclinic VO2 (M) core and outer V2O5 shell, which is the first example of photoconductive IR detector made from transition metal oxides (TMOs), is presented. Benefited from the well-defined TMO hetero­junction interface, the ultrahigh responsivity (Rλ) of 2873.7 A W-1 and specific detectivity (D*) of 9.23 × 1012 Jones are achieved at room temperature (at 990 nm; 0.2 mW cm-2), recording the best performance compared with those reported IR detectors based on heavy-metal-free materials, and even comparable/superior to those traditional ones made from materials including heavy metals. These findings pave a new way to design oxide heterostructures for intriguing applications in optoelectronic and energy harvesting nanodevices.

A gold nanoparticles/TiO 2 composite modified Indium tin oxide (ITO) electrode has been constructed to study the electrochemical behaviour of catechol (CC) and hydroquinone (HQ) using cyclic voltammetry and differential pulse voltammetry (DPV). Increasing of separation of the oxidative peak potentials and peak current for CC and HQ in pH 6.0 phosphate buffer solution (PBS), make it suitable for selected determination of CC. After the optimization of the conditions, CC was determined by DPV and the linear range is from 1.0 × 10 −7 to 5.0 × 10 −4 mol L −1 with a correlation coefficient of 0.999 and limit of detection as 5.0 × 10 −8 mol L −1 . Interference and stability study showed a satisfactory result. The proposed method has been applied to determine catechol in tea samples, and comparing with the chromatography the results are satisfactory.

Hypoxic tissue exists in most of the solid tumors and hypoxia is a common character of these tumors. The existence of hypoxic tissue in the tumor decreases the efficacy of radiotherapy and chemotherapy. Radiolabeled hypoxia markers have been developed to measure the hypoxic tissue together with non-invasive imaging techniques such as PET, SPECT, and PET/CT. This offers a convenient approach to delineate the tumor providing useful information for diagnosing cancer and guiding the treatment plan. Bioreducible or-ganic compounds have been developed as the hypoxia markers to probe tissue hypoxia noninvasively because they can be reduced and metabolized under hypoxic conditions; form adducts with cell components, and thus be trapped in the hypoxic tissue. These compounds include nitroimidazoles and other redox-sensitive compounds such as BnAO and ATSM. Different radionuclides have been used to label these compounds such as technetium-99m, iodine-123, fluorine-18, copper-64, etc. In addition, to detect hypoxia with endogenous hypoxia markers such as carbonic anhydrase IX (CA IX) and hypoxia-inducible factor-1 (HIF-1), some radiolabeled tracers have also been developed. This article is an overview of the progress in this area in the past decade including the development of radiolabeled compounds for hypoxia detection and problems associated with the hypoxia marker development.

The reaction of low-energy electrons (LEEs; 10 eV) with 5'-TpXpT-3' (TXT), where X is uracil (U), thymine (T), and 5-bromouracil (5BrU), was examined by HPLC-UV analysis. The presence of 5BrU increased total damage by >50%. The radiation products of T5BrUT included TUT (40%), free U, T, 5BrU (23%), and fragments (13%). These products may be explained by initial capture of LEEs by the nucleobase to form a transient anion, followed by transfer of the electron within the molecule and cleavage of susceptible bonds by dissociative electron attachment (C-Br, C-N, or C-O bonds). In addition, these products may arise from the uracilyl-5-yl (U-5-yl) radicals that undergo H-atom abstraction from the sugar moiety. Interestingly, several products contained two sites of cleavage (U, pUT, and TUp). The formation of these products was linear with dose, and thus, they arise from the single-electron reactions. To explain these products, we propose that the reaction of LEEs (10 eV) involves the coupling of two dissociative processes in the same molecule (for example, dissociative excitation and dissociative electron attachment). The latter reactions may contribute to the formation of clustered damage, which is the most deleterious damage induced by ionizing radiation.

The novel nickel-based catalysts with a nickel content of 12 wt% were prepared with the zirconia-alumina composite as the supports. The new carriers, ZrO 2 improved alumina, were synthesized by three methods, i.e., impregnation-precipitation, co-precipitation, and impregnation method. The catalytic properties of these catalysts were investigated in the methanation of carbon dioxide, and the samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS), temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) techniques. The new catalysts showed higher catalytic activity and better stability than Ni/γ-Al 2 O 3 . Furthermore, as a support for new nickel catalyst, the ZrO 2 -Al 2 O 3 composite prepared by the impregnation-precipitation method was more efficient than the other supports in the methanation of carbon dioxide. The highly dispersed zirconium oxide on the surface of γ-Al 2 O 3 inhibited the formation of nickel aluminate-like phase, which was responsible for the better dispersion of Ni species and easier reduction of NiO species, leading to the enhanced catalytic performance of corresponding catalyst.

The fabrication of Nano-Au/Porous-TiO2 composite modified glassy carbon electrode (GCE) and its application in the determination of hydrazine were proposed. The morphological characterization was examined by transmission electron microscope and scanning electron microscopy. The Nano-Au/Porous-TiO2/GCE exhibited a wide linear range of hydrazine from 2.5 to 500 μM, with a detection limit of 0.5 μM at a signal-to-noise ratio of 3 and with a fast response time (within 3 s). Furthermore, the reaction mechanism of the hydrazine on the Nano-Au/Porous-TiO2/GCE was explored. The ease of fabrication, high stability, and low cost of the modified electrode are the promising features of the proposed sensor.

DNA damage induced by low-energy electrons (LEEs) has attracted considerable attention in recent years because LEEs represent a large percentage of the total energy deposited by ionizing radiation and because LEEs have been shown to damage DNA components. In this article, we have studied the effect of base sequences in a series of oligonucleotide trimers by the analysis of damage remaining within the nonvolatile condensed phase after LEE irradiation. The model compounds include TXT, where X represents one of the four normal bases of DNA (thymine (T), cytosine (C), adenine (A), and guanine (G)). Using HPLC-UV analysis, several known fragments were quantified from the release of nonmodified nucleobases (T and X) as well as from phosphodiester C-O bond cleavage (pT, pXT, Tp, and TXp). The total damage was estimated by the disappearance of the parent peaks in the chromatogram of nonirradiated and irradiated samples. When trimers were irradiated with LEE (10 eV), the total damage decreased 2-fold in the following order: TTT > TCT > TAT > TGT. The release of nonmodified nuclobases (giving from 17 to 24% of the total products) mainly occurred from the terminal sites of trimers (i.e., T) whereas the release of central nucleobases was minor (C) or not at all detected (A and G). In comparison, the formation of products arising from phosphodiester bond cleavage accounted for 9 to 20% of the total damage and it partitioned to the four possible sites of cleavage present in trimers. This study indicates that the initial LEE capture and subsequent bond breaking within the intermediate anion depend on the sequence and electron affinity of the bases, with the most damage attributed to the most electronegative base, T.

N -[4-(Benzothiazol-2-yl)phenyl]-11-(2-nitroimidazole-1-yl)undecanamide (2NUBTA) was synthesized and radiolabeled with iodine-131. In vitro evaluation of the [ 131 I]2NUBTA using murine sarcoma S180 cells showed increase in radioactivity in hypoxic cells up to 4 h, while it was not in aerobic cells. Its potential as a cerebral ischemia marker was evaluated using gerbil stroke models that had been subjected to right common carotid artery ligation to produce cerebral ischemia. The uptake in the right cerebral hemisphere decreased slowly than that of the left and the right/left hemisphere uptake ratios increased with time going on. It indicated that [ 131 I]2NUBTA might be a possible cerebral ischemia marker.

Berberine was iodized by iodine monochloride, followed by an isotopic exchange reaction with Na125I. The radiochemical purity and in vitro and in vivo stability were quite satisfactory. The biodistribution in mice showed that the concentration of 125I-labeled berberine was high in the gallbladder and gastrointestinal system, as compared to other organs. Berberine was metabolized in the liver, partly excreted through the hepatobiliary tract, and underwent a process of hepatoenteral circulation. Its main route of elimination was renal excretion. Blood concentrationtime curve was fitted with an open two-compartment model. The plasma protein binding rate was (48±3.8)%. The results indicated that the radioiodinated berberine has similar in vivo behavior and pharmacokinetics to berberine reported before. The novel radioiodination is a convenient method to study in vivo behavior of such alkaloids.

Ag/13X adsorbents were synthesized, characterized and tested for decontamination of gaseous effluents from 131I2 at high temperatures. X-ray diffraction patterns showed that the Ag/13X samples maintained a stable structure after calcined at 650 °C for 2 h. The decontamination factors achieved with 15 % Ag/13X and 20 % Ag/13X adsorbents for 131I2 were nearly close to 103 at 650 °C. In addition, 15 % Ag/13X had a stable performance for removal of 131I2 at 550 and 650 °C, even after calcined at 550 and 650 °C for over 10 h, which might be suitable for future potential use during nuclear reactor operation or in the case of nuclear accidents.

Low-energy electrons (LEE) induce single- and double-strand breaks in DNA. To investigate the mechanism of LEE-induced DNA damage, nucleotides and short oligonucleotide were irradiated with monoenergetic electrons in the solid state and the modifications were observed by chemical analyses. With 10 eV electrons and TpTpT as the target, approximately one-third of the total damage of TpTpT involves cleavage of the phosphodiester-sugar bond (C-O) and the N-glycosidic bond (C-N). Here we focus on the remaining two-thirds of the damage. The major products were observed to elute between TpT and TpTpT on the HPLC chromatogram. Of these products, three modifications were identified as XpTpT, TpXpT and TpTpX, where X = 5,6-dihydrothymine, on the basis of comparison with standard compounds using HPLC and mass spectrometry. These results suggest that 5,6-dihydrothymine is a major product of the reaction of LEE with DNA.

We have investigated the role of two selected amino acids, glycine and arginine, on damage induced to a short chain of single stranded DNA, the tetramer GCAT, during 1 eV electron exposure. At this energy, DNA has a high cross section for DNA damage via exclusively dissociative electron attachment. Surprisingly, at low ratios of glycine : GCAT, an increase in the total fragmentation yield is observed, whilst at higher ratios, glycine and arginine appear to protect DNA from the direct action of electrons. In addition, binding energies were calculated by molecular modelling of the interactions between these amino acids and either nucleobases or nucleotides. These binding energies appear to be related to the ability of amino acids to protect DNA against low energy electron damage.

Since 2003, H5N1 influenza viruses have caused over 400 known cases of human infection with a mortality rate greater than 60%. Most of these cases resulted from direct contact with virus-contaminated poultry or poultry products. Although only limited human-to-human transmission has been reported to date, it is feared that efficient human-to-human transmission of H5N1 viruses has the potential to cause a pandemic of disastrous proportions. The genetic basis for H5N1 viral transmission among humans is largely unknown. In this study, we used guinea pigs as a mammalian model to study the transmission of six different H5N1 avian influenza viruses. We found that two viruses, A/duck/Guangxi/35/2001 (DKGX/35) and A/bar-headed goose/Qinghai/3/2005(BHGQH/05), were transmitted from inoculated animals to naïve contact animals. Our mutagenesis analysis revealed that the amino acid asparagine (Asn) at position 701 in the PB2 protein was a prerequisite for DKGX/35 transmission in guinea pigs. In addition, an amino acid change in the hemagglutinin (HA) protein (Thr160Ala), resulting in the loss of glycosylation at 158–160, was responsible for HA binding to sialylated glycans and was critical for H5N1 virus transmission in guinea pigs. These amino acids changes in PB2 and HA could serve as important molecular markers for assessing the pandemic potential of H5N1 field isolates., Author Summary H5N1 influenza viruses have caused over 400 human infections in 15 countries and continue to circulate in poultry and wild birds. Most human infections resulted from direct contact with virus-contaminated poultry or poultry products. It would be disastrous if H5N1 viruses acquired the ability to efficiently transmit among humans, because the mortality rate may exceed 60%. However, the genetic basis for transmission of H5N1 influenza viruses is largely unknown. Here, we demonstrate that the amino acid residue at 701 of PB2 is a prerequisite for transmission of H5N1 viruses in a mammalian guinea pig model. Interestingly, we found that the absence of glycosylation at residues 158–160 of the HA gene is pivotal for the H5N1 virus to bind to human-like receptors and to transmit in a mammal host. These findings are important for assessing the pandemic potential of H5N1 field isolates.

The nucleoprotein (NP), which has multiple functions during the virus life cycle, possesses regions that are highly conserved among influenza A, B, and C viruses. To better understand the roles of highly conserved NP amino acids in viral replication, we conducted a comprehensive mutational analysis. Using reverse genetics, we attempted to generate 74 viruses possessing mutations at conserved amino acids of NP. Of these, 48 mutant viruses were successfully rescued; 26 mutants were not viable, suggesting a critical role of the respective NP amino acids in viral replication. To identify the step(s) in the viral life cycle that is impaired by these NP mutations, we examined viral-genome replication/transcription, NP localization, and incorporation of viral-RNA segments into progeny virions. We identified 15 amino acid substitutions in NP that inhibited viral-genome replication and/or transcription, resulting in significant growth defects of viruses possessing these substitutions. We also found several NP mutations that affected the efficient incorporation of multiple viral-RNA (vRNA) segments into progeny virions even though a single vRNA segment was incorporated efficiently. The respective conserved amino acids in NP may thus be critical for the assembly and/or incorporation of sets of eight vRNA segments.

Low energy electrons (LEE) induce DNA damage by dissociative electron attachment, which involves base release (N-glycosidic bond (N-C) cleavage) and the formation of strand breaks (phosphodiester-sugar bond (C-O) cleavage). The effect of terminal phosphate and base moieties was assessed by exposing DNA model compounds to LEE in the condensed phase followed by HPLC-UV analysis of products remaining on the surface. First, we report that the presence of terminal phosphate groups in monomers (pT, Tp, pTp) and dimers (pTpT, TpTp, pTpTp) increases overall damage by 2-3-fold while it decreases N-C and C-O bond cleavage by 2-10-fold. This suggests that the capture of LEE directly by the terminal phosphate does not contribute to N-C and C-O bond cleavage. Second, we report that terminal bases appear to shield the internal base from damage, resulting in a bias of damage toward the termini. In summary, the presence of terminal phosphate base moieties greatly affects the distribution of LEE induced damage in DNA model compounds.

Timely imaging and accurate interpretation of cerebral ischemia are required to identify patients who might benefit from more aggressive therapy, and nuclear medicine offers a noninvasive method for demonstrating cerebral ischemia. Three nitroimidazole-based thioflavin-T derivatives,N-[4-(benzothiazol-2-yl)phenyl]-3-(4-nitroimidazole-1-yl) propanamide (4NPBTA),N-[4-(benzothiazol-2-yl)phenyl]-3-(4-nitroimidazole-1-yl)-N-methylpropanamide (4NPBTA-1), andN-[4-(benzothiazol-2-yl)phenyl]-3-(2-nitroimidazole-1-yl) propanamide (2NPBTA), were radioiodinated and evaluated as possible cerebral ischemia markers. In normal mice, these compounds showed good permeation of the intact blood-brain barrier (BBB), high initial brain uptake, and rapid washout. In gerbil stroke models that had been subjected to right common carotid artery ligation to produce cerebral ischemia, [I131]2NPBTA, uptake in the right cerebral hemisphere decreased more slowly than that of the left, and the right/left hemisphere uptake ratios increased with time. Also, the right/left hemisphere uptake ratios correlated positively with the severity of the stroke. The results showed that [I131]2NPBTA had a specific location in the cerebral ischemic tissue. This represented a first step in finding new drugs and might provide a possible cerebral ischemic marker.

Three novel nitroimidazole-based thioflavin-T derivatives, N-[4-(benzothiazol-2-yl)phenyl]-3-(4-nitroimidazole-1-yl)propanamide, N-[4-(benzothiazol-2-yl) phenyl]-3-(4-nitroimidazole-1-yl)-N-methylpropanamide and N-[4-(benzothiazol-2-yl)phenyl]-3-(2-nitroimidazole-1-yl) propanamide were synthesized and radiolabeled with iodine-131. Three (131)I-labeled compounds continuously accumulated in hypoxic murine sarcoma S180 cells in vitro but not in aerobic cells. Biodistribution results in mice bearing S180 tumor indicated that the tracers could localize in the tumor and eliminate from it slowly. In contrast, the uptake in other organs (stomach excluded) was little and the clearance was quick. The tumor-to-tissue ratios of three compounds all increased with time.