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Reversible folding/unfolding of small α-helix in explicit solvent investigated by ABEEMσπ/MM

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Science china chemistry 2009年第11期52卷 1917-1924页

作者： LIU Cui & YANG ZhongZhi chemistry and chemical engineering Faculty,Liaoning Normal University,dalian 116029,china chemistry and chemical engineering Faculty Liaoning Normal University Dalian China

We have performed molecular dynamics simulations on the reversible folding/unfolding of small α-helix(short Ala based peptide Ala5) in explicit water solvent in terms of ABEEMσπ/MM.A dynamics analysis shows that the α-helical turn can be preserved up to a period of about 2 ns at 300 K,which supports the conclusions of Margulis et *** time trajectory of the root mean square deviation between the heavy atoms of the backbone and the helical reference structure indicate that "helix melting and formation occurs rapidly on a time scale of 0.1 ns at 300 K" is not a felicitous *** first quantificationally concluded that the helix nucleation can maintain 2 ns,1―1.5 ns and 0.8 ns for Ala5 at 300 K,400 K and 500 K,***,increasing temperature dose not alter the pathway of folding/unfolding,but change the *** analysis of structures in a "transition-state ensemble" shows that helix-to-coil transitions occurs predominantly through breaking of hydrogen bonds at the helix ends(92%),particularly at the C-terminus(50%).Hydrogen bonds' breaking and formation occurs on a time scale of 0.1 ns.

关键词： reversible folding/unfolding of protein Ala5 temperature hydrogen bond

Application of the ABEEM/MM model in studying the properties of the water clusters(H_2O)_n(n=7-10)

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Science china chemistry 2007年第2期50卷 190-204页

作者： QIAN Ping & YANG ZhongZhi Faculty of chemistry and chemical engineering,Liaoning Normal University,dalian 116029,china Faculty of chemistry and chemical engineering Liaoning Normal University Dalian China

ABEEM/MM model has been applied to compute the various properties characterizing water clusters(H2O) n(n = 7-10) ,such as optimized geometries,the hydrogen bonds number,cluster interaction en-ergies,stabilities,ABEEM charge distributions,dipole moments,structural parameters,and so on,and to describe the transition reflected by the hexamer region from two-dimensional(from dimer to pen-tamer) to three-dimensional structures(for clusters larger than the hexamer) .

关键词： ABEEM/MM model the atom-bond electronegativity equalization method molecular mechanics water clusters

Size effect of fullerene cages and encaged clusters in M3N@C2n

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Science china chemistry 2009年第5期52卷 584-589页

作者： GAN LiHua school of chemistry and chemical engineering, Southwest University, Chongqing 400715, china school of chemistry and chemical engineering Southwest University Chongqing China

Based on the calculated findings that the sizes of encaged clusters determine the structures and the stability of C80-based trimetallic nitride fullerenes (TNFs), more extensive density functional theory calculations were performed on M3N@C68, M3N@C78 and M3N@C80 (M=Sc, Y and La). The calculated results demonstrated that the structures and stability undergo a transition with the increasing of the sizes of the cages and clusters. Sc3N is planar inside the three considered cages, Y3N is slightly pyramidal inside C68-6140 and C78-5 and planar inside I h C80-7, however, La3N is pyramidal inside all the three cages. Those cages with pyramidal clusters inside deformed considerably, compared with their parent cages. In these cases, the bonding of metallic atoms toward the cages does not play an impor-tant role, and the encaged cluster tends to be located inside the cages with the largest M-M and M-C distances so that the strain energy can be released mostly. These calculations revealed the size effect of fullerene cages and encaged clusters, and can explain the position priority of M3N inside fullerene cages and the differences in yield of M3N@C2n.

关键词： trimetallic nitride fullerenes (TNFs) density functional theory (DFT) size effect stability

Theoretical study of bifurcated bent blue-shifted hydrogen bonds CH_2…Y

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Science china chemistry 2008年第7期51卷 623-631页

作者： LI AnYong school of chemistry and chemical engineering, Southwest University, Chongqing 400715, china school of chemistry and chemical engineering Southwest University Chongqing China

Ab initio quantum chemistry methods were applied to study the bifurcated bent hydrogen bonds Y… H2CZ (Z = O, S, Se) and Y…H2CZ2 (Z = F, Cl, Br) (Y = Cl-, Br-) at the MP2/6-311++G(d,p) and MP2/6-311++G(2df,2p) levels. The results show that in each complex there are two equivalent blue-shifted H-bonds Y…H—C, and that the interaction energies and blue shifts are large, the energy of each Y…H—C H-bond is 15-27 kJ/mol, and Δr(CH) = -0.1 - -0.5 pm and Δv(CH) = 30 - 80 cm-1. The natural bond orbital analysis shows that these blue-shifted H-bonds are caused by three factors: large rehybridization; small direct intermolecular hyperconjugation and larger indirect intermolecular hy- perconjugation; large decrease of intramolecular hyperconjugation. The topological analysis of elec- tron density shows that in each complex there are three intermolecular critical points: there is one bond critical point between the acceptor atom Y and each hydrogen, and there is a ring critical point inside the tetragon YHCH, so these interactions are exactly H-bonding.

关键词： bifurcated bent H-bonds blue-shifted H-bonds topological property of electron density intramolecular hyperconjugation

Boron rings containing planar octa- and enneacoordinate cobalt, iron and nickel metal elements

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Science china chemistry 2008年第7期51卷 607-613页

作者： LUO Qiong school of chemistry and chemical engineering, Central South University, Changsha 410083, china school of chemistry and chemical engineering Central South University Changsha China

For a series of boron rings with planar hyper-coordinate 8th group transition metal atoms, singlet 1FeB8-2, multiplet kFeB9n (n = -1, k = 1; n = 0, k = 2), singlet 1CoB8n(n = -1, +1, +3), multiplet kCoB9n (n = +1, k = 2; n = 0, k = 1) and singlet 1NiB9+, the geometry structures have been optimized to be local minima on corresponding potential hyper-surfaces. The electron structures are discussed by orbital analysis and the aromaticity is predicted by nucleus-independent chemical shifts calculation at both the B3LYP/6-311+G* and BP86/6-311+G* levels of theory, respectively. The results suggest that all these structures with high symmetry planar geometries are stable and have aromatic properties with six π valence electrons.

关键词： planar hyper-coordinate transition metal DFT

Catalytic oxidation of soot particulates over MnO_x-CeO_2 oxides prepared by complexation-combustion method

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Journal of Natural Gas chemistry 2010年第1期19卷 86-90页

作者： Wenjuan Shan, Na Ma, Jiali Yang, Xiaowei Dong, Chang Liu, Lingling Wei Institute of chemistry for Functionalized Materials, College of chemistry and chemical engineering, Liaoning Normal University, dalian 116029, Liaoning, china Institute of chemistry for Functionalized Materials College of Chemistry and Chemical Engineering Liaoning Normal University Dalian 116029 Liaoning China

MnOx-CeO2 oxides prepared by complexation-combustion method were used for soot oxidation. The highest conversion rate of soot was obtained on a MnOx-CeO2 oxide prepared under mild acid condition of pH = 4, where the oxidation temperature corresponding to maximum activity was decreased more than 150 ℃ compared with that of un-catalytic soot oxidation. The structure and property of the catalysts were investigated by X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）. The results indicated that there were at least two kinds of Mn species present in MnOx-CeO2 catalysts, i.e. Mn ions within CeO2 lattice and high dispersion MnOx on the surface of CeO2. The presence of Mn ions in the CeO2 lattice improved the oxygen vacancy due to the charge difference, and the CeO2 considerably decreased the reduction temperature of MnOx. The capability to activate oxygen through the oxygen exchange between O2 in gas phase and lattice oxygen species in MnOx-CeO2 oxide contributed to the high catalytic activity for the reaction.

关键词： soot oxidation MnOx-CeO2 oxides active oxygen

Influence of steric and intramolecular inductive effects on the variable trends in R-X (R=Alkyl) bond dissociation energy

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Science china chemistry 2009年第7期52卷 943-951页

作者： CAO ChenZhong school of chemistry and chemical engineering, Hunan University of Science and Technology, Xiangtan 411201, china school of chemistry and chemical engineering Hunan University of Science and Technology Xiangtan China

The question "why are the variation trends of R-X bond dissociation energy different?" is answered. The R-X bond dissociation energy (BDE) may be influenced by three main factors: the C-X intrinsic bond energy, the 1,3 geminal repulsion, and the intramolecular charge-induced dipole. In the presence of atom X, the variation trend of BDE in R-X (R= Me, Et, i-Pr, t-Bu) is dominated by two factors, the 1,3 geminal repulsion and the intramolecular charge-induced dipole. The former decreases the R-X BDE, and the latter either increases or decreases the R-X BDE. For the series of R-X with the R-C bond (such as R-Me, R-CH == CH2, R-C≡CH, and R-CN), the 1,3 geminal repulsion decreases the R-X BDE, and the variation trends of R-C BDE decrease from Me to t-Bu. As regards the series of R-X (such as R-H, R-BH2, and R-SiH2) in which the electronegativity of atom X is smaller than that of the carbon atom, the above two factors decrease the R-X BDE, and the variation trends of the R-X BDE decrease from Me to t-Bu. As to the series of R-X (such as R-F, R-OH, R-Cl, R-Br, R-I, and R-NH2) in which the electronegativity of atom X is larger than that of the carbon atom, the 1,3 geminal repulsion decreases the R-X BDE, while the intramolecular charge-induced dipole increases the R-X BDE. In this case, the variation trends of R-X BDE depend on the competition of the two factors. As a result, some of them (e. g., R-F, R-OH) increase from Me to t-Bu, some (e. g., R-I) decrease from Me to t-Bu, and some (e. g., R-Br) change very little.

关键词： bond dissociation energy charge-induced dipole geminal repulsion ionic configuration

Electrochemical behaviour of commercially pure titanium and Co-Cr alloy in Ringer's solution

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Rare Metals 2002年第4期21卷 266-270页

作者： LIANG Chenghao and MOU Thanqischool of chemical engineering, dalian University of Technology, dalian 116012, china school of chemical engineering Dalian University of Technology Dalian 116012

The electrochemical behaviors of commercially pure titanium (CP Ti) and Co-Cralloy in Ringer's solution have been investigated. The results indicate that the electric potentialof passive region for CP Ti is up to 3000 mV, and its passive current density is 3.078 μA/cm^*** excellent corrosion resistance of CP Ti can be attributed to the formation of TiO_2 oxide *** passive region of Co-Cr alloy is 770 mV, which is narrower than that of CP Ti. However, nohysteresis loops are found in the reverse scanning curves of Cu-Cr alloy. A complex oxide film ofCo_3O_4, Co_2O_3, and Cr_2O_3 formed on the surface provides Co-Cr alloy with a stableelectrochemistry property. The corrosion rates of the crevice samples increase with the pH value ofmedium decreasing. The electron probe microanalyzer (EPMA) analysis indicates that Ti in CP Ti andCo, Cr in Co-Cr alloy dissolve in crevice area due to the Sealed-Cell effect.

关键词： ringer's solution biomedical material electrochemical behaviors

Meet Our New Editorial Board Members of Rising Stars

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Chinese Journal of chemistry 2024年第16期42卷 1797-1805页

作者： Editorial Office of Chinese Journal of chemistry 不详

Editorial Board Memberof Rising Stars:Xiulin Fan,Professor,school of Materials Science and engineering Zhejiang University,Hangzhou,***:2003-2007,*** University,china.2007-2012,*** University,china(Supervisor:*** Chen).

关键词： china. Editorial Hangzhou