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Tao Yu, Maohua Lin, Bo Wu, Jintian Wang, Chi-Tay Tsai
On the basis of the framework of cubic gauche nitrogen (cg-N), six one-eighth methanetriyl groups (>CH-) substitutes and fifteen one-fourth >CH- substitutes were optimized using the first-principle calculations based on density functional theory (DFT). Both one-eighth and one-fourth substitutes still keep the gauche structures with the simple formula CHN7 and CHN3 , respectively. The most thermodynamic stable gauche CHN7 and CHN3 are P21 qtg-C2 H2 N14 I and P21 qtg-C4 H4 N12 III, respectively. No probability density of C-C single bonds and high probability densities of C-N-C structures were found in the two substitutes...
May 16, 2018: Journal of Molecular Graphics & Modelling
Asad Ayub Rajput, Zeshan, Chettiyappan Visvanathan
Hard lignocellulosic structure of wheat straw is the main hindrance in its anaerobic digestion. Thus, a laboratory scale batch experiment was conducted to study the effect of thermal pretreatment on anaerobic digestion of wheat straw. For this purpose, different thermal pretreatment temperatures of 120, 140, 160 and 180 °C were studied and the results were compared with raw wheat straw. Significant differences in biogas production were observed at temperature higher than 160 °C. Highest biogas yield of 615 Nml/gVS and volatile solids reduction of 69% was observed from wheat straw pretreated at 180 °C...
May 21, 2018: Journal of Environmental Management
T Yadav, V Mukherjee
The present work deals with the conformational and vibrational spectroscopic study of an important bio-molecule named norepinephrine in gas phase. The FTIR and FTRaman spectrum of norepinephrine in amorphous form were recorded in wavenumber range 4000-400 cm-1 and 4000-50 cm-1 respectively. We have investigated twenty-seven stable conformational structures of norepinephrine molecule. All the calculations have been done using Density Functional Theory with exchange functional B3LYP incorporated with the 6-31++G(d, p) basis set...
May 21, 2018: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Yibei Wan, Xiao Liu, Penglei Liu, Lei Zhao, Weihua Zou
Polydopamine microspheres (PDMPs) synthesized by a facile solution oxidation method were adopted as a potential adsorbent for the removal of Norfloxacin (NOR) from aqueous solution. The morphologies and properties of PDMPs were characterized using TEM, SEM, FTIR and pHPZC . Parameters effects such as contact time, initial pH, initial concentration and ionic strength on the adsorption capacity of NOR onto PDMPs were studied. To maximize NOR removal from liquid phase, Box-Behnken experimental design (BBD) combined with response surface modeling (RSM) was employed based on the 17 preliminary experiments at 308 K...
May 21, 2018: Science of the Total Environment
Kai Hung Huang, Tsung-Han Tu, Shi-Cheng Wang, Yi-Tsu Chan, Cheng-Chih Hsu
Supramolecular diblock copolymers using metal-ligand coordination can be synthesized under ambient conditions by delicate design of the end groups of the homopolymer chains. However, mass spectrometric analysis of such metallo-supramolecular copolymers is challenging. One of the reasons is the nonpolarity of the polymer chains, making it hard to disperse the complexes in electrospray ionization (ESI)-friendly environments. The other difficulty is the noncovalent nature of such copolymers, which is easily disrupted during the ionization...
May 24, 2018: Analytical Chemistry
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
Alessandro Palmioli, Barbara La Ferla
A set of poly(lactic- co-glycolic acid) polymers functionalized with different monosaccharides as well as glycodendrimers and surface-decorated nanoparticles (NPs) were synthesized and characterized. The functionalization of the polymer was carried out through amide bond formation with amino-modified sugar monomers and through a biocompatible chemoselective method exploiting the reducing end of a free sugar. The assemblage of the NPs adopting a nanoprecipitation method was straightforward and allowed the preparation of sugars/sugar dendrimer coated NPs...
May 24, 2018: Organic Letters
James S Klimavicz, Konstantin Röder, David J Wales
Single-stranded DNA structures play a significant role in biological systems, in particular during replication, translation and DNA repair. Tracts of simple repetitive DNA (srDNA) are associated with slipped-strand mispairing (SSMs), that can lead to genetic diseases. Recent NMR studies of TTTA and CCTG repeats have shown that these sequences form mini-dumbbells (MDBs), leading to frameshift mutations. Here we explore the energy landscapes of (CCTG)2 and (TTTA)2 , which are currently the smallest known molecules to form MDBs...
May 24, 2018: Journal of Chemical Theory and Computation
Ryan D Dolewski, Patrick J Fricke, Andrew McNally
Many drug fragments and therapeutic compounds contain multiple pyridines and diazines. Developing site-selective reactions where specific C-H bonds can be transformed in polyazine structures would enable rapid access to valuable derivatives. We present a study that addresses this challenge by selectively installing a phosphonium ion as a versatile functional handle. Inherent factors that control site-selectivity are described along with mechanistically driven approaches for site-selective switching, where the C-+PPh3 group can be predictably installed at other positions in the polyazine system...
May 24, 2018: Journal of the American Chemical Society
Yvonne Lorenz, Albert Gutiérrez, Montserrat Ferrer, Marianne Engeser
A series of selectively self-assembled metallo-supramolecular square-like macrocycles with unsymmetric ditopic linkers and two different types of metal corners, i.e., {Pd(η3 -2-Me-C3 H4 )} and {M(dppp)} with dppp = 1,3-bis(diphenylphosphino)propane and M = Pd2+ or Pt2+ , have been studied in the gas phase using collision-induced dissociation. The aggregates show distinct fragmentation patterns determined by ligand length, i.e, aggregate size, and type of metal corner. Information on relative binding strength can be deduced...
May 24, 2018: Inorganic Chemistry
Gema Cabello, Rogério A Davoglio, Luis G Cuadrado
Herein, we report a detailed study of microwave-matter interaction focused on the role of small nanoparticles and the effects on microwave thermal heating. We have used a model reaction (degradation of methylene blue) to study the influence of temperature, size, and catalytic properties of the nanoparticles in the potential formation of hot spots. Total mineralization was achieved after 3 h microwave heating at 200 °C in the presence of 2 nm TiO2 nanoparticles (92% calculated TOC decay), but the reaction resulted in a mixture of intermediates (52% TOC decay) in the absence of TiO2 ...
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
Daozhong Zhang, Zhijun Tang, Wen Liu
Natural products typically are small molecules produced by living organisms. These products possess a wide variety of biological activities and thus have historically played a critical role in medicinal chemistry and chemical biology either as chemotherapeutic agents or as useful tools. Natural products are not synthesized for use by human beings; rather, living organisms produce them in response to various biochemical processes and environmental concerns, both internal and external. These processes/concerns are often dynamic and thus motivate the diversification, optimization, and selection of small molecules in line with changes in biological function...
May 24, 2018: Accounts of Chemical Research
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
Raffaella Mancuso, Christian S Pomelli, Piera Chiappetta, Katia Francesca Gioia, Asif Maner, Nadia Marino, Lucia Veltri, Cinzia Chiappe, Bartolo Gabriele
The cycloisomerization of readily available 2-alkynylbenzoic acids 1 in ionic liquids (ILs) as recyclable reaction media has been studied under the catalytic action of CuCl2. With substrates bearing an aryl group on the triple bond, a mixture of (Z)-3-alkylideneisobenzofuran-1(3H)-ones (from 5-exo-dig cyclization) and 1H-isochromen-1-ones (from 6-endo-dig cyclization) was observed in 1-ethyl-3-methylimidazolium ethyl sulfate (EmimEtSO4), while the reaction turned out to be selective toward the formation of the isobenzofuranone only using N-ethyl-N-methylmorpholinium dicyanamide [Mor1,2N(CN)2], as the solvent...
May 24, 2018: Journal of Organic Chemistry
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
Conghui Yuan, Tong Wu, Jie Mao, Ting Chen, Yuntong Li, Min Li, Yiting Xu, Birong Zeng, Weiang Luo, Lingke Yu, Gaofeng Zheng, Lizong Dai
Core-shell structures are of particular interest in the development of advanced composite materials as they can efficiently bring different components together at nanoscale. The advantage of this structure greatly relies on the crucial design of both core and shell, thus achieving an inter-component synergistic effect. In this report, we show that decorating semiconductor nanocrystals with a boronate polymer shell can easily achieve programmable core-shell interactions. Taking ZnO and anatase TiO2 nanocrystals as inner core examples, the effective core-shell interactions can narrow the band gap of semiconductor nanocrystals, change the HOMO and LUMO levels of boronate polymer shell and significantly improve the carrier density of core-shell particles...
May 24, 2018: Journal of the American Chemical Society
Kentaro Aoki, Kazuya Otsubo, Garry S Hanan, Kunihisa Sugimoto, Hiroshi Kitagawa
Neutral triangular macrocyclic compounds, [PdX2 (4,7-phen)]3 ·(DMF)3 ·Et2 O (X = Cl, Br; 4,7-phen = 4,7-phenanthroline; DMF = N, N'-dimethylformamide; Et2 O = diethyl ether), were synthesized, and their molecular structures were characterized. Solution-state 1 H NMR results suggested the formation of metal-ligand bonds, and single-crystal X-ray crystallography revealed clear triangular structures. A detailed examination of the structures indicated the formation of two kinds of cavities in the solid state, where a triangular unit works as a halogen-based receptor for polar and apolar solvents through weak hydrogen-bonding and dipole-dipole interaction...
May 24, 2018: Inorganic Chemistry
Lingjun Ma, Aude Annie Watrelot, Bennett Addison, Andrew L Waterhouse
Numerous monomeric and oligomeric flavanol sulfonation products were observed in 10 wines. Levels of 0.85-20.06 mg/L and 0-14.72 mg/L were quantified for two monomeric sulfonated flavan-3-ols, and surprisingly, were generally higher than the well-known native flavan-3-ol monomers. Increasing SO2 levels during wine aging increased the sulfonate modified flavan-3-ol monomers and dimers along with higher concentrations of native monomers. The results indicate that >10% of SO2 is reacting with the C4 carbocation, formed from acid cleavage of the interflavan bond, perhaps by a bimolecular SN2 type reaction, and as a reducing agent...
May 24, 2018: Journal of Agricultural and Food Chemistry
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