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Duangtip Sudhan, Thamrongjet Puttamuk, Supachai Vuttipongchaikij, Pitak Chuawong
Citrus Huanglongbing (HLB) or citrus greening is one of the most destructive diseases affecting citrus industry worldwide. The causal agent in Asia is a phloem-limited, Gram-negative bacterium, 'Candidatus Liberibacter asiaticus' (CLas). Within the genome of CLas lies prophage regions, classified as Type-A, B, C, and D. In particular, Type-D has been indicated to correlate with the blotchy-mottle symptoms of citrus trees. Here we reported the cloning, overexpression, and purification of the ORF1, an open reading frame from the partial Type-D region of CLas obtained from an infected lime tree (Citrus aurantifolia Swingle)...
May 21, 2018: Protein Expression and Purification
Yihong Xu, Shaoming Pan, Jianhua Gao, Xiaolin Hou, Yongfu Ma, Yongpei Hao
Plutonium (Pu) isotopes were first determined in surface and core sediment samples collected from the northern North Yellow Sea (NYS) to elucidate their source terms and deposition process as well as the response to catchment environmental changes of inflow rivers. 240 Pu/239 Pu atom ratios in all sediments showed the typical global fallout value of ∼0.18 without any influences from the nuclear weapons tests conducted recently in the North Korea or early in the Pacific Proving Ground. The large variation of 239+240 Pu activities (0...
May 18, 2018: Chemosphere
Yuji Shimabukuro, Hidenori Takahashi, Shinichi Iwamoto, Koichi Tanaka, Motoi Wada
A thermal cracking cell that served as the atomic hydrogen source for hydrogen attachment/abstraction dissociation (HAD) analysis has an intrinsic problem to produce a beam of atoms reactive against heated tungsten capillary. A plasma excited by 2.45 GHz microwave power can deliver reactive species to a quadrupole ion trap confining analyte ions without excessive heating of the radical source components. The radical (H•) production performance of the developed source was evaluated by optical emission spectroscopy and H• attachment reaction to fullerene ions...
May 24, 2018: Analytical Chemistry
Thiago Sousa, Thales Fernando Damasceno Fernandes, Matheus J S Matos, Eduardo Nery Duarte Araujo, Mario S C Mazzoni, Bernardo R A Neves, Flávio Plentz
The association of organic molecules with 2D materials, creating hybrid systems with mutual influences, constitutes an important testbed for both basic science self-assembly studies and perspective applications. Following this concept, in this work, we show a rich phenomenology that is involved in the interaction of thionine with graphene, leading to a hybrid material formed by well-organized self-assembled structures atop graphene. This composite system is investigated by atomic force microscopy, electric transport measurements, and first principles calculations, which show: 1) an interesting time evolution of thionine self-assembled structures atop graphene; 2) the final molecular assembly is highly oriented (in accordance with the underlying graphene surface symmetry); and 3) thionine introduces a strong n-type doping effect in graphene...
May 24, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Jun Shang, Ben Hu, Junmei Wang, Feng Zhu, Yu Kang, Dan Li, Huiyong Sun, De-Xin Kong, Tingjun Hou
This is a new golden age for the drug discovery based on natural products derived from both marine and terrestrial sources. Herein, a straightforward but important question is what are the major structural differences between marine natural products (MNPs) and terrestrial natural products (TNPs). To answer this question, we analyzed the important physicochemical properties, structural features and drug-likeness of the two types of natural products and discussed their differences from the perceptive of evolution...
May 24, 2018: Journal of Chemical Information and Modeling
Hidenori Takahashi, Yuji Shimabukuro, Daiki Asakawa, Shosei Yamauchi, Sadanori Sekiya, Shinichi Iwamoto, Motoi Wada, Koichi Tanaka
Gas-phase hydrogen radicals were introduced into a quadrupole ion trap containing singly charged phospholipids to obtain structural fragmentation patterns in tandem mass spectrometry (MS/MS). Saturated and unsaturated phosphatidylcholines were used as a model phospholipid, whose chain-length ranges between 16 and 24. The MS/MS spectrum yielded a continuous series of fragment ions with a mass differencesdifference of 14 Da, representing the saturated fatty acyl chains. The fragment ions corresponding to the double-bond position within a single fatty acyl chain showed thea characteristic mass difference of 12 Da...
May 24, 2018: Analytical Chemistry
Elizabeth Peterson, Christine Joseph, Hannah Peterson, Rachael Bouwman, Shengzhuang Tang, Jayme Cannon, Kumar Sinniah, Seok Ki Choi
Multivalent ligand-receptor interaction provides the fundamental basis for the hypothetical notion that high binding avidity relates to the strong force of adhesion. Despite its increasing importance in the design of targeted nanoconjugates, an understanding of the physical forces underlying the multivalent interaction remains a subject of urgent investigation. In this study, we designed three vancomycin (Van)-conjugated dendrimers G5(Van)n (n = mean valency = 0, 1, 4) for bacterial targeting with generation 5 (G5) poly(amidoamine) dendrimer as a multivalent scaffold, and evaluated both their binding avidity and physical force of adhesion to a bacterial model surface by employing surface plasmon resonance (SPR) spectroscopy and atomic force microscopy (AFM)...
May 24, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Rex T Skodje, Jonathan R Church
A novel double hydrogen atom exchange process, HX+H'O2H'X+HO2 for the halogen series X=F, Cl, Br, and I, is identified using theoretical methods. These concerted reactions are mediated through a stabilized five-member planar ring transition state structure. The transition state barrier for the double exchange process is found to be significantly lower than that for the abstraction reaction of a single hydrogen atom, . Density functional theory employing the M11 exchange functional is used to compute parameters of the potential energy surface and the rate coefficients are obtained using transition state theory with small curvature tunneling...
May 24, 2018: Journal of Physical Chemistry. A
Federica Battistin, Gabriele Balducci, Barbara Milani, Enzo Alessio
As a continuation of our strategy for preparing new Ru(II) precursors with improved water solubility through the introduction of highly water-soluble 1,3,5-triaza-7-phosphoadamantane (PTA) supporting ligands in the coordination sphere, in this work, we address the largely unexplored preparation of Ru(II)-PTA carbonyls. Two complementary synthetic approaches were used: (1) the treatment of a series of neutral Ru(II)-CO-dmso compounds of general formula RuCl2 (CO) n (dmso)4- n ( n = 1-3, 1-5) with PTA; (2) the reaction of Ru(II)-PTA complexes with CO...
May 24, 2018: Inorganic Chemistry
Priscilla L S Boon, Wuan Geok Saw, Xin Xiang Lim, Palur Venkata Raghuvamsi, Roland G Huber, Jan K Marzinek, Daniel A Holdbrook, Ganesh S Anand, Gerhard Grüber, Peter J Bond
The 11 kDa, positively charged dengue capsid protein (C protein) exists stably as a homodimer and co-localizes with the viral genome within mature viral particles. Its core is composed of four alpha helices encompassing a small hydrophobic patch that may interact with lipids, but approximately 20% of the protein at the N-terminus is intrinsically disordered, making it challenging to elucidate its conformational landscape. Here, we combine small-angle X-ray scattering (SAXS), amide hydrogen-deuterium exchange mass spectrometry (HDXMS), and atomic-resolution molecular dynamics (MD) simulations to probe the dynamics of dengue C proteins...
May 24, 2018: ACS Chemical Biology
Bin Yang, Youai Qiu, Jan-E Bäckvall
Oxidation reactions play a central role in organic synthesis, and it is highly desirable that these reactions are mild and occur under catalytic conditions. In Nature, oxidation reactions occur under mild conditions via cascade processes, and furthermore, they often occur in an enantioselective manner with many of them involving molecular oxygen or hydrogen peroxide as the terminal oxidant. Inspired by the reactions in Nature, we have developed a number of Pd(II)-catalyzed cascade reactions under mild oxidative conditions...
May 24, 2018: Accounts of Chemical Research
James A Dawson, Pieremanuele Canepa, Theodosios Famprikis, Christian Masquelier, M Saiful Islam
No abstract text is available yet for this article.
May 24, 2018: Journal of the American Chemical Society
Qiaofeng Yao, Tiankai Chen, Xun Yuan, Jianping Xie
Total synthesis, where desired organic- and/or biomolecules could be produced from simple precursors at atomic precision and with known step-by-step reactions, has prompted centuries-lasting bloom of organic chemistry since its conceptualization in 1828 (Wöhler synthesis of urea). Such expressive science is also highly desirable in nanoscience, since it represents a decisive step toward atom-by-atom customization of nanomaterials for basic and applied research. Although total synthesis chemistry is less established in nanoscience, recent years have witnessed seminal advances and increasing research efforts devoted into this field...
May 24, 2018: Accounts of Chemical Research
Libin Wang, Le Deng, Jieming Qin, Xiaopeng Jia
It has been discussed for a long time that synthetic pressure can effectively optimize thermoelectric properties. The beneficial effect of synthesis pressures on thermoelectric properties has been discussed for a long time. In this paper, it is theoretically and experimentally demonstrated that appropriate synthesis pressures can increase the figure of merit (ZT) through optimizing thermal transport and electronic transport properties. Indium and barium atoms double-filled CoSb3 samples were prepared use high-pressure and high-temperature technique for half an hour...
May 24, 2018: Inorganic Chemistry
Prasanna Pakkiam, Matthew Gregory House, Dr Matthias Koch, Michelle Y Simmons
We present a donor based quadruple quantum dot device, designed to host two singlet-triplet qubits fabricated by scanning tunnelling microscope lithography, with just two leads per qubit. The design is geometrically compact with each pair of dots independently controlled via one gate and one reservoir. The reservoirs both supply electrons for the dots and measure the singlet-triplet state of each qubit via dispersive sensing. We verify the locations of the four phosphorus donor dots via an electrostatic model of the device...
May 24, 2018: Nano Letters
Alexander S Mikherdov, Mikhail A Kinzhalov, Alexander S Novikov, Vadim P Boyarskiy, Irina A Boyarskaya, Margarita S Avdontceva, Vadim Yu Kukushkin
The reaction of cis-[PdCl2 (CNXyl)2 ] (Xyl = 2,6-Me2 C6 H3 ) with the aminoazoles [1 H-imidazol-2-amine (1), 4 H-1,2,4-triazol-3-amine (2), 1 H-tetrazol-5-amine (3), 1 H-benzimidazol-2-amine (4), 1-alkyl-1 H-benzimidazol-2-amines, where alkyl = Me (5), Et (6)] in a 2:1 ratio in the presence of a base in CHCl3 at RT proceeds regioselectively and leads to the binuclear diaminocarbene complexes [(ClPdCNXyl)2 {μ-C(N-azolyl)N(Xyl)C═NXyl}] (7-12; 73-91%). Compounds 7-12 were characterized by C, H, N elemental analyses, high-resolution ESI+ -MS, Fourier transform infrared spectroscopy, 1D (1 H, 13 C) and 2D (1 H,1 H-COSY, 1 H,1 H-NOESY, 1 H,13 C-HSQC, 1 H,13 C-HMBC) NMR spectroscopies, and X-ray diffraction (XRDn)...
May 24, 2018: Inorganic Chemistry
Pengfei Li, Wei Zhang, Dongdong Li, Changhao Liang, Xiao Cheng Zeng
The most stable structures of two-dimensional (2D) GexPy and GexAsy monolayers with different stoichiometry (e.g., GeP, GeP2, GeP3) are explored systematically through the combination of the particle-swarm optimization (PSO) technique and density functional theory optimization. For GeP3, we show that the newly predicted most stable C2/m structure is 0.16 eV/atom lower in energy than the state-of-the-art P-3m1 structure reported previously (Nano Lett.2017, 17, 1833). The computed electronic band structures suggest that all the stable and metastable monolayers of GexPy are semiconductors with highly tunable bandgaps under the biaxial strain, allowing strain engineering of their bandgaps within nearly the whole visible-light range...
May 24, 2018: ACS Applied Materials & Interfaces
Sabine Wagner, Carlos Zapata, Wei Wan, Kornelia Gawlitza, Marcus Weber, Knut Rurack
Small-molecule oxoanions are often imprinted noncovalently as carboxylates into molecularly imprinted polymers (MIPs), requiring the use of an organic counterion. Popular species are either pentamethylpiperidine (PMP) as a protonatable cation or tetraalkylammonium (TXA) ions as permanent cations. The present work explores the influence of the TXA as a function of their alkyl chain length, from methyl to octyl, using UV/vis absorption, fluorescence titrations and HPLC, as well as MD simulations. Protected phenylalanines (Z-L/D-Phe) served as templates/analytes...
May 23, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Ashish Bhattarai, Andrey Krayev, Alexey Temiryazev, Dmitry Evplov, Kevin Thomas Crampton, Wayne P Hess, Patrick Z El Khoury
Tip-enhanced Raman spectroscopy (TERS) is particularly sensitive to analytes residing at plasmonic tip-sample nanojunctions, where the incident and scattered optical fields may be localized and optimally enhanced. However, the enhanced local electric fields in this so-called gap-mode TERS configuration are nominally orthogonal to the sample plane. As such, any given Raman active vibrational Eigenstate needs to have projections (of its polarizability derivative tensor elements) along the sample normal to be detectable via TERS...
May 23, 2018: Nano Letters
Seyyed Hossein Asadpour, Hamid Reza Hamedi, Mahmoud Jafari
This paper hints at the Goos-Hänchen shift properties of a cavity containing an ensemble of atoms using a four-level atomic system involving a Rydberg state. By means of the stationary phase theory and density matrix formalism in quantum optics, we study theoretically the Goos-Hänchen shifts in both reflected and transmitted light beams. It is realized that as a result of the interaction between Rydberg and excited states in such a four-level atom-light coupling scheme the maximum positive and negative Goos-Hänchen shifts can be obtained in reflected and transmitted light beams owning to the effect of the Rydberg electromagnetically induced transparency (EIT) or Rydberg electromagnetically induced absorption...
May 20, 2018: Applied Optics
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