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12/2013;
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ABSTRACT: Calculations were performed to study the interactions of metal ions (M) with (multiple) amino acids (AA) and fill the gap between single AA and proteins. A complete conformational search results in nine and eleven ZnGly isomers at B3P86 and MP2 levels, respectively, and four populated conformers of glycine are responsible for production of these isomers. For all M, the isomers via the OO and NO binding modes are the main constituents, and the OO mode is favored by stronger electrostatic interactions. Binding with more glycines causes larger structural distortions, improves relative stabilities of monodentate binding isomers and generates new binding modes (e.g. ZnB(III) via only the hydroxyl group). The scaling factor of Zn(Gly)(n) structures, the ratio of its binding affinity versus the sum of comprising ZnGly isomers, is linear with glycine number (n), and the linear relationship may not be altered by mutations of glycines and M. It thus allows to estimate M(AA)(n) binding affinities (n ≥ 2) from the comprising MAA structures and analyze their structures with kinetic methods. The DFT and MP2 results become comparable by increasing metal coordination, e.g. the ZnB(III) versus ZnA(I) (zwitterionic) relative energy differs by 41.9 kcal mol(-1) at B3P86 and MP2 levels and is close by addition of three water molecules (4.1 kcal mol(-1) ). The presence of water solvent improves the relative stabilities of monodentate binding isomers and results in a broader conformational distribution. Copyright © 2012 John Wiley & Sons, Ltd.
Biological Mass Spectrometry 10/2012; 47(10):1372-83. · 3.41 Impact Factor
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Theoretical Chemistry Accounts 05/2012; 131(5):1299. · 2.16 Impact Factor
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ABSTRACT: The ferroelectric phase behaviors of modified BaTiO3 in X7R multilayer ceramic capacitors (MLCCs) were investigated by dielectric measurements and in situ Raman scattering. The
in situ thermo-Raman scattering shows that because of a residual stress existing in the MLCCs, the tetragonal to cubic phase
transition for modified BaTiO3 in MLCCs takes place over a wide temperature range of 373K to 473K, suggesting a diffuse-like characteristic which can
be well explained by a modified phenomenological thermodynamic model, while the dielectric measurement indicates that the
tetragonal to cubic transition occurs at 393K. A disagreement exists between the two experimental results. Furthermore, a
dc field-induced paraelectric to ferroelectric transition was identified by the two measurement techniques, but their phase-transition
mechanisms are different. The dielectric measurement reveals the polar-micro-region to macro-domain transformation in the
shell part of the core–shell structure while the in situ Raman scattering shows the cubic to tetragonal transition under a
dc bias field.
Applied Physics A 05/2012; 91(1):119-125. · 1.63 Impact Factor
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ShengFa Liu,
XueFa Shi,
YanGuang Liu,
ShuQing Qiao, Gang Yang,
XiSheng Fang,
YongHua Wu,
ChaoXin Li,
XiaoYan Li,
AiMei Zhu,
JingJing Gao
[show abstract]
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ABSTRACT: AMS14C dating and analysis of grain size, major elements and clay minerals were applied to Core MZ01 from the mud area on the inner
shelf of the East China Sea. Based on the environmentally sensitive grain size, clay mineral and major element assemblages,
the history of the East Asia winter monsoon since the mid-Holocene could be reconstructed. These three proxies, mean grain
size (>9.71 μm), chemical index of alteration (CIA) and ratio of smectite to kaolinite in particular, show similar fluctuation
patterns. Furthermore, 10 extreme values corresponding to the contemporary cooling events could be recognized since the mid-Holocene;
these extreme values are likely to have been caused by the strengthening of the East Asia winter monsoon. The cooling events
correlated well with the results of the δ18O curves of the Dunde ice core and GISP2, which therefore revealed a regional response to global climate change. Four stages
of the East Asia winter monsoon were identified, i.e. 8300–6300 a BP, strong and unstable; 6300–3800 a BP, strong but stable;
3800–1400 a BP, weak and unstable; after 1400 a BP, weak but stable.
KeywordsHolocene-inner shelf of the East China Sea-mud areas-grain size-clay mineral-elemental analysis-East Asia winter monsoon
Chinese Science Bulletin 04/2012; 55(21):2306-2314. · 1.32 Impact Factor
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ABSTRACT: Gas hydrate research has significant importance for securing world energy resources, and has the potential to produce considerable
economic benefits. Previous studies have shown that the South China Sea is an area that harbors gas hydrates. However, there
is a lack of systematic investigations and understanding on the distribution of gas hydrate throughout the region. In this
paper, we applied mineral resource quantitative assessment techniques to forecast and estimate the potential distribution
of gas hydrate resources in the northern South China Sea. However, current hydrate samples from the South China Sea are too
few to produce models of occurrences. Thus, according to similarity and contrast principles of mineral outputs, we can use
a similar hydrate-mining environment with sufficient gas hydrate data as a testing ground for modeling northern South China
Sea gas hydrate conditions. We selected the Gulf of Mexico, which has extensively studied gas hydrates, to develop predictive
models of gas hydrate distributions, and to test errors in the model. Then, we compared the existing northern South China
Sea hydrate-mining data with the Gulf of Mexico characteristics, and collated the relevant data into the model. Subsequently,
we applied the model to the northern South China Sea to obtain the potential gas hydrate distribution of the area, and to
identify significant exploration targets. Finally, we evaluated the reliability of the predicted results. The south seabed
area of Taiwan Bank is recommended as a priority exploration target. The Zhujiang Mouth, Southeast Hainan, and Southwest Taiwan
Basins, including the South Bijia Basin, also are recommended as exploration target areas. In addition, the method in this
paper can provide a useful predictive approach for gas hydrate resource assessment, which gives a scientific basis for construction
and implementation of long-term planning for gas hydrate exploration and general exploitation of the seabed of China.
Keywordgas hydrate-resource assessment-northern South China Sea-Gulf of Mexico
Chinese Journal of Oceanology and Limnology 04/2012; 28(3):693-699. · 0.50 Impact Factor
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ABSTRACT: A new amino-containing phthalonitrile derivative 4-(4-(3, 5-diaminobenzoyl) phenoxy) phthalonitrile (DAPN) was successfully
synthesized. Its structure was identified by FT-IR and 1H-NMR. DAPN can be thermally polymerized by duration at 230°C for various times under a nitrogen atmosphere, even in the
absence of curing additives. The thermal properties of the cured products were characterized by TGA and DSC. The 5 and 10%
weight loss temperatures ranged from 442 to 446 and 504 to 505°C, respectively. Char yields (800°C) were in the range of
72.7–72.9%. DSC data showed that the melting peak of the cured products disappeared due to their thermal polymerization. The
insolubility in concentrated sulfuric acid and FT-IR of the cured products indicated the formation of cross-linked networks.
Polymer Bulletin 04/2012; 62(5):581-591. · 1.53 Impact Factor
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ABSTRACT: In this paper, we study the problem of a variety of nonlinear time series model X
n+1 = T
Z
n+1(X(n), …, X(n − Z
n+1), e
n+1(Z
n+1)) in which {Z
n
} is a Markov chain with finite state space, and for every state i of the Markov chain, {e
n
(i)} is a sequence of independent and identically distributed random variables. Also, the limit behavior of the sequence {X
n
} defined by the above model is investigated. Some new novel results on the underlying models are presented.
Acta Mathematicae Applicatae Sinica 04/2012; 26(1):159-168. · 0.29 Impact Factor
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ABSTRACT: Fe/ZSM-5 zeolite has shown great potential in the selective oxidations of hydrocarbons such as methane and benzene. The various
competing active sites of Fe/ZSM-5 zeolite are reviewed, including the mono-iron, oxygen-bridged [Fe, X] (X=Fe, Al) and
peroxide species; in addition, the influences of H2 pretreatment are considered. For the mono-iron species, the H2 molecules are chemisorbed on the Fe(III) sites via the η2-binding mode. Both high- and low-spin Fe(III) ions play an important role during the H2 reduction process whereas the former predominates in the N2O decomposition process. As the calculated energy barriers indicate, the Fe(III) ions are facile to be reduced by H2 pretreatment and therefore the active site of the mono-iron species should be in the FeO(OH) form. Instead, the oxygen-bridged
[Fe, X] and peroxide species remain stable by H2 pretreatment. The suitable oxygen-bridged [Fe, X] structures are screened out by comparisons with the experimental data and
energy considerations from computational aspects. The geometries are in good agreement with the experimental data; meanwhile,
it provides sound explanations to the distribution of the iron valence states, the thermodynamic facilitation of the “alfa-oxygen”
generation by the introduction of extra-lattice Al ions as well as the shift of the Fe–Fe distances from ca. 3.06 to 2.53Å.
The superoxide species exists in Fe/ZSM-5 zeolite but not with the presence of extra-lattice Al ions. As the temperature increases,
it gradually converts into the peroxide species and probably is the precursor of the peroxide species, one of the competing
active sites in Fe/ZSM-5 zeolite. The clarification of active sites lays a solid foundation on the understanding of the catalytic
processes and improvement of the Fe/ZSM-5 catalyst, one of the promising candidates to meet the industry challenges.
KeywordsActive sites-Fe/ZSM-5 zeolite-Theoretical calculations-H2 pretreatment-N2O decomposition
Catalysis Surveys from Asia 04/2012; 14(2):85-94. · 1.90 Impact Factor
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ABSTRACT: Metal ions are ubiquitous in protein systems and play a significant role during their folding processes. Nineteen independent structures were determined for the Na(+)/β-hairpin interacting systems, and their folding pathways are different. (i) For Na(S47), the turn is rapidly shaped with the help of Na(+) and acts as the folding nucleus for the rest regions. Two intermediate states are observed and the resulted structure is the most folded. (ii) For Na(B41), Na(B52), Na(B54), Na(S55) and Na(B56), the inclusive Na(+) ions are anchored by β-strands. The local structures around the Na(+) ions and the turn regions fold simultaneously and serve as two independent folding nuclei. (iii) The other systems have no folding nuclei and correspond to low-folded structures. Long-range electrostatic interactions contribute a lot to the folding, especially from the four negatively charged residues (Glu42, Asp46, Asp47 and Glu56). The initial positions of the Na(+) ions are largely responsible for the different folding behaviors. The interactions with sidechain- rather than backbone-O atoms generally lead to more compact structures. Another factor affecting the folding is whether the O atoms are associated with native H-bonds, and those involved show decreased affinities to metal ions. The addition of water solvent does not induce obvious folding and conformational transitions to the Na(+)/β-hairpin interacting systems.
Computational biology and chemistry 03/2012; 38:1-9. · 1.37 Impact Factor
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Comput. Biol. Chem. 03/2012;
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Mol. Simulat. 02/2012; 38(2):161-171.
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Comput. Theor. Chem. 10/2011; 973(1-3):1-8.
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ABSTRACT: Two gravity cores collected off the modern Huanghe (Yellow River) delta in the southern Bohai Sea were analyzed for grain size, the total organic carbon (TOC)/total nitrogen (TN) ratio, color diffraction, magnetic susceptibility, 14C dating and 137Cs and 210Pb isotope contents to clarify changes in the sedimentary environment during the Holocene. In particular, the effect of natural and artificial river-course shifts of the Huanghe on the Bohai Sea sediment was investigated. A peat layer, scouring surface and sharp changes in the grain size, TOC/TN ratio, sediment color (L⁎, a⁎) and magnetic susceptibility were identified and are likely to be due to the early-Holocene sea-level rise resulting in environmental changes from coastal to shelf environments in the Bohai Sea. After the sea level reached its maximum at 6–7 ka BP, the lateral shifts in the river course of the Huanghe formed 10 superlobes, and superlobe 7 (11–1048 AD) and superlobe 10 (1855–present) of the Huanghe delta affected the core sites. The northern site of BH-239 has been more affected by the Huanghe since the middle Holocene. Notably, in the superlobe 10 period, the reshaping of the northern Huanghe delta due to an artificial river-course shift from northward to eastward in 1976 (e.g., a∼10 km shoreline retreat due to coastal erosion) was recorded in the core sediments, particularly in terms of the TOC/TN ratio, sediment color (L⁎ and a⁎) and magnetic susceptibility, owing to the huge sediment supply from coastal erosion of the former river mouth area.Highlights► Changes in the sedimentary environment off the modern Huanghe delta were studied. ► Early-Holocene sea-level rises were well recorded. ► The Huanghe river-course shifts related to superlobes 7 and 10 were recognized. ► The artificial river-course shift in 1976 was well preserved.
Continental Shelf Research 09/2011; 31(13):1336-1342. · 2.09 Impact Factor
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ABSTRACT: The chiral recognitions between various neuraminidases (NA) and 5-[(1R,2S)-1-(acetylamino)-2- methoxy-2-methylpentyl]-4-[(1Z)-1-propenyl)-(4S,5R)]-D-proline (BL) stereoisomers have been theoretically studied. The zwitterions of BL are responsible for the bioactivities, and electrostatic rather than van der Waals (vdW) contributions play a significant role. With the presence of NA proteins, the orders of relative stabilities of the BL stereoisomers are greatly altered; meanwhile, the ranges are significantly enlarged, ensuring the respective recognitions of the BL9z, BL3z, BL2z, and BL1z stereoisomers by the N1, N2, N9 subtype, and B type NA proteins. It is mainly due to geometric complementarities of the NA active sites with the BL carboxyl and propenyl groups. The recognitions of proteins with chiral ligands are rather targeted, even applicable to N2 and N9 with high structural similarities. Thus, the significance of chirality is addressed for the designs of anti-influenza drugs, which aids our understanding of chiral recognitions between proteins and ligands. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011
International Journal of Quantum Chemistry 03/2011; 112(3):909 - 921. · 1.36 Impact Factor
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ABSTRACT: Isolated Ti species in zeolites show unique catalytic activities for a variety of chemical reactions. In this work, density functional calculations were used to explore three current concerns: 1) the distributions of Ti(IV) and Ti(III) ions in the MCM-22 zeolite; 2) the Lewis acidity of the Ti(IV) and Ti(III) sites; and 3) activation of alkane C-H bonds by photocatalysis with Ti-doped zeolites. Neither the Ti(IV) nor Ti(III) ions are randomly distributed in the MCM-22 zeolite. The orders of relative stability are very close for the eight Ti(IV) and Ti(III) sites, and the T3 site is the most probable in both cases. The wavelengths for Ti(IV)-Ti(III) excitations were calculated to lie in the range λ=246.9-290.2 nm. The Ti3(IV) site shows Lewis acidity toward NH(3) in two different modes, and these two modes can coexist with each other. The calculated Ti(IV) coordination numbers, Ti(IV)-O bond elongations, and charge transfers caused by NH(3) adsorption are in good agreement with previous results. Similarly, two different NH(3) adsorption modes exist for the Ti3(III) site; the site that exhibits radical transfer from the lattice O to N atoms is preferred due to the higher adsorption energy. This indicates that the Ti3(III) site does not show Lewis acidity, in contrast to the Ti3(IV) site. At the Ti3(III) site, the energy barrier for activating the methane C-H bond was calculated to be 33.3 kJ mol(-1) and is greatly reduced by replacing the hydrogen atoms with methyl groups. In addition, the reactivity is improved when switching from MCM-22 to TS-1 zeolite. The studies on the various Ti species reveal that lattice O atoms rather than Ti(III) radicals are crucial to the activation of alkane C-H bonds. This work provides new insights into and aids understanding of the catalysis by isolated Ti species in zeolites.
Chemistry 02/2011; 17(5):1614-21. · 5.93 Impact Factor
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ABSTRACT: Docking and molecular dynamics were used to study the nine ligands (see Scheme 1) at the neuraminidase (NA) active sites. Their binding modes are structurally and energetically different, with details given in the text. Compared with 1A (oseltamivir carboxylate), the changes of core template or/and functional groups in the other ligands cause the reductions of interaction energies and numbers of H-bonds with the NA proteins. Nonetheless, all these ligands occupy the proximity space at the NA active sites and share some commonness in their binding modes. The fragment approach was then used to analyze and understand the binding specificities of the nine ligands. The contributions of each core template and functional group were evaluated. It was found that the core templates rather than functional groups play a larger role during the binding processes; in addition, the binding qualities are determined by the synergistic effects of the core templates and functional groups. Among the nine ligands, 1A (oseltamivir carboxylate) has the largest synergistic energy and its functional groups fit perfectly with the NA active site, consistent with the largest interaction energy, numerous H-bonds with the NA active-site residues as well as experimentally lowest IC(50) value. Owing to the poorer metabolizability than oseltamivir, large contribution of the benzene core template and fine synergistic effects of the functional groups, the 4-(N-acetylamino)-5-guanidino-3-(3-pentyloxy)benzoic acid should be an ideal lead compound for optimizing NA drugs.
Journal of Theoretical Biology 12/2010; 267(3):363-74. · 2.21 Impact Factor
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ABSTRACT: In the present study, anti-IBV (infectious bronchitis virus) activity of 1,8-cineole was studied by MTT assay, as well as docking and molecular dynamic (MD) simulations. The CC50 of 1,8-cineole was above 10 mM. And the maximum noncytotoxic concentration (TD0) of 1,8-cineole was determined to be 3.90 ± 0.22 mM, which was much higher than that of ribavirin (0.78 ± 0.15 mM). 1,8-cineole could inhibit IBV with an IC(50) of 0.61 mM. MTT assay showed that the inhibition of IBV by 1, 8-cineole appears to occur moderately before entering the cell but much strongly after penetration of the virus into the cell. In silico simulations indicated that the binding site of 1,8-cineole was located at the N terminus of phosphorylated nucleocapsid (N) protein, with interaction energy equaling -40.33 kcal mol(-1). The residues TyrA92, ProA134, PheA137, AspA138 and TyrA140 had important roles during the binding process and are fully or partially conserved in various IBV strains. Based on spatial and energetic criteria, 1,8-cineole interfered with the binding between RNA and IBV N-protein. Results presented here may suggest that 1,8-cineole possesses anti-IBV properties, and therefore is a potential source of anti-IBV ingredients for the pharmaceutical industry.
Journal of biomolecular structure & dynamics 12/2010; 28(3):323-30. · 4.99 Impact Factor
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ABSTRACT: This article investigated the effects of electron beam (EB) irradiation on poly(D,L-lactic acid)-b-poly(ethylene glycol) copolymer (PLEG) and poly(L-lactic acid) (PLLA). The dominant effect of EB irradiation on both PLEG and PLLA was chain scission. With increasing dose, recombination reactions or partial crosslinking of PLEG can occur in addition to chain scission, but there was no obvious crosslinking for PLLA at doses below 200 kGy. The chain scission degree of irradiated PLEG and PLLA was calculated to be 0.213 and 0.403, respectively. The linear relationships were also established between the decrease in molecular weight with increasing dose. Elongation at break of the irradiated PLEG and PLLA decreased significantly, whereas the tensile strength and glass transition temperature of PLLA decreased much more significantly compared with PLEG. The presence of poly(ethylene glycol) (PEG) chain segment in PLEG was the key factor in its greater stability to EB irradiation compared with PLLA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011
Journal of Applied Polymer Science 10/2010; 120(1):509 - 517. · 1.29 Impact Factor
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Advances in Environmental Research 04/2010; 4(4-75-79):75-79.
