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ABSTRACT: Like human immunodeficiency virus (HIV), equine infectious anaemia virus (EIAV) belongs to the lentivirus genus. The first successful lentiviral vaccine was developed for EIAV. Thus, EIAV may serve as a valuable model for HIV vaccine research. EIAV glycoprotein 45 (gp45) plays a similar role to gp41 in HIV by mediating virus-host membrane fusion. The gp45 ectodomain was constructed according to the structure of HIV gp41, with removal of the disulfide-bond loop region. The protein was expressed in Escherichia coli and crystallized following purification. However, most of the crystals grew as aggregates and could not be used for data collection. By extensively screening hundreds of crystals, a 2.7 Å resolution data set was collected from a single crystal. The crystal belonged to space group P6(3), with unit-cell parameters a = b = 46.84, c = 101.61 Å, α = β = 90, γ = 120°. Molecular replacement was performed using the coordinates of various lengths of HIV gp41 as search models. A long bent helix was identified and a well defined electron-density map around the long helix was obtained. This primary model provided the starting point for further refinement.
Acta Crystallographica Section F Structural Biology and Crystallization Communications 04/2011; 67(Pt 4):482-5. · 0.51 Impact Factor
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ABSTRACT: Constructing eukaryotic expressing vector of pMT/Bip/V5-His A-HIV gp120 and transfecting S2 cells to establish stable gp120-expressing S2 cell line. The gp120 gene of HIV CRF07-BC epidemic in China was amplified by polymerase chain reaction from the recombinant vector PRSV-gp120 and confirmed by DNA sequence analysis. The DNA fragment of HIV gp120 was digested with the restriction endonucleases NcoI and XhoI, then inserted into eukaryotic expressing vector pMT/BiP/V5-His A. A selection vector containing the streptomyces griseochromogenes bsd gene conferring blasticidin resistance was cotransfected into drosophila S2 cells by Cellfectin II reagent. The stable cell line was established following repeated screening by blasticidin. HIV gp120 was purified by a Ni-NTA affinity column followed by molecular sieve chromatography. Recombinant protein was characterized by SDS-PAGE, Western blot and ELISA. The eukaryotic expressing vector pMT/BiP/V5-His A-HIV gp120 was constructed, stable expressing cell line was established, and protein was expressed and purified successfully. This result will contribute to functional study of gp120 and vaccine design against AIDS.
Bing du xue bao = Chinese journal of virology / [bian ji, Bing du xue bao bian ji wei yuan hui] 11/2010; 26(6):460-4.
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ABSTRACT: In our previous work (J. Phys. Chem. A 2008, 112, 8877.), we found theoretical evidence indicating UF5OH is an intermediate produced in the first step of UF6 hydrolysis. In this work, we explored the probable reaction channels starting from UF5OH + UF6 and UF5OH + UF5OH systems using relativistic density functional theory calculations. Initially, the two uranium containing species associate to form complex UF6.UF5OH or dimer (UF5OH)2 through hydrogen bonding. The energy released is 12-16 kcal/mol, which may promote further reactions. After H2O or HF are eliminated from the complex or dimer, compounds containing U-O-U bond are produced. These compounds are potentially feasible to associate into larger clusters or solidify. Relative to the isolated initial species, the energies of the final products are -6 to -13 kcal/mol lower, indicating that the reactions may spontaneously proceed. The calculated IR spectra features can be used to indicate the formation and interaction type of the intermediates and products.
The Journal of Physical Chemistry A 09/2009; 113(32):9243-8. · 2.95 Impact Factor
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ABSTRACT: The mechanism of the gas-phase reaction UF 6 + H 2O --> UOF 4 + 2HF is explored using relativistic density functional theory calculations. Initially, H 2O coordinates with UF 6 to form a 1:1 complex UF 6.H 2O. Over an activation energy barrier of about 19 kcal/mol, H 2O transfers a H atom to a nearby ligand F, resulting in UF 5OH + HF. The eliminated HF or another H 2O molecule may form a hydrogen bond with UF 5OH. Starting from UF 5OH, the second HF elimination results in UOF 4. If UF 5OH is in the isolated form, UF 5OH --> UOF 4 + HF takes place over a barrier of 24 kcal/mol. If UF 5OH is hydrogen-bonded with H 2O or HF, the conversion barrier is less than 10 kcal/mol. Once formed, the unstable UOF 4 tends to associate with additional ligands and hydrogen-bonding donors. The calculated binding energies indicate the significance of such interactions, which may have profound impact on further HF eliminating reactions. The IR spectra features can be used to indicate the formation and interaction type of the intermediates and products.
The Journal of Physical Chemistry A 10/2008; 112(37):8877-83. · 2.95 Impact Factor
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ABSTRACT: UV-Vis spectra of the aqueous solutions of 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole (1) at different pH values revealed that compound 1 is a tertiary base, which can combine three protons. Through the non-linear least square method, the logarithm of the three accumulative protonation constants of compound 1, namely, lgbeta1, lgbeta2 and lgbeta3, were determined to be 4.96 +/- 0.03, 5.72 +/- 0.07 and 7.95 +/- 0.10, respectively. UV-Vis and the steady-state fluorescence spectra indicated that a special interaction occurs between compound 1 and calf thymus DNA at the pH value of 3.40, of which thebinding constant, Kb, is (2.30 +/- 0.10) x 10(4) mol(-1) x L. Compound 1 in the concentration range of 10(-8) to 1.2 x 10(-6) mol x L(-1) has a potential application to the quantitative determination of DNA.
Guang pu xue yu guang pu fen xi = Guang pu 11/2005; 25(10):1618-21. · 0.84 Impact Factor
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ABSTRACT: Gas-phase decomposition of formic acid results in final products CO + H2O and CO2 + H2. Experimentally, the CO/CO2 ratio tends to be large, in contradiction with mechanism studies, which show almost equal activation energies for dehydration and decarboxylation. In this work, the influence of H2 on the decomposition mechanism of HCOOH was explored using ab initio calculations at the CCSD(T)/6-311++G**//MP2/6-311++G** level. It was found that, in the presence of H2, the reaction channels leading to CO + H2O are more than those leading to CO2 + H2. With competitive energy, H2 addition to HCOOH can reduce the latter into HCHO, which then dissociates into CO + H2 catalyzed by H2O. Compared to trans-HCOOH, cis-HCOOH and cis-C(OH)2, conformers required for decarboxylation, are less populated due to interactions with H2.
The Journal of Physical Chemistry A 11/2005; 109(40):9129-40. · 2.95 Impact Factor
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Journal of Physical Organic Chemistry 02/2005; 18(7):625 - 631. · 1.96 Impact Factor
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ABSTRACT: A new potential pharmaceutical compound, 2-(4-dimethylaminophenyl)-5-fluoro-6-(morpholin-4-yl)-1H-benzimidazole (4) was synthesized. The effect of the pH value of aqueous solution on the absorption spectrum of compound 4 and its interaction with beta-cyclodextrin (beta-CD) were investigated by UV-Vis spectrum, steady-state fluorescence and time-resolved spectroscopic measurements. The results indicate that compound 4 mainly exists in neutral molecular state when pH value of the aqueous phase is above 7.0. In the pH range from 7.0 to 3.8 the neutral molecular state and protonated univalent cationic form coexist. As the pH value decreases, the content of univalent cationic form increases. When 2.76 < pH < 3.8, the protonated univalent cationic form is the predominant species. With further decrease of the pH value, the univalent cation is protonated by another H+ to form a bivalent cation, and both univalent and bivalent cations coexist in the solution. The steady-state fluorescence and time-resolved spectroscopic measurements revealed that compound 4 is a sensitive molecular probe. The interaction of compound 4 and beta-CD is very strong. The guest:host ratio of inclusion complex between compound 4 and beta-CD formed in the aqueous solution (pH = 9.50) is 1:1, and the association constant was determined to be (1.02 +/- 0.04) x 10(3) mol x L(-1).
Guang pu xue yu guang pu fen xi = Guang pu 06/2004; 24(5):588-91. · 0.84 Impact Factor
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ABSTRACT: Gas-phase reactions between silane (SiH4) and water (H2O) were investigated using ab initio calculations at the CCSD(T)/6-311++G**//MP2/6-31+G* level. Within the energy range of 160 kcal/mol, we located 40 equilibrium and 27 transition states on the potential energy surfaces of the Si−O−H systems. Over an energy barrier of 46.61 kcal/mol, the weakly bonded molecular complex SiH4−H2O can eliminate first H2 molecule and produce silanol (SiH3OH). The transition state is a dihydrogen-bonded structure with retention of the silane configuration. The total energy of the direct products SiH3OH + H2 is −10.83 kcal/mol relative to the reactants. Over an energy barrier of 58.09 kcal/mol, SiH4−H2O can eliminate first H2 and produce a transient dative bonded complex SiH2−H2O. Providing more energy to the system, SiH4−H2O can dissociate atomically and the initial products can further eliminate H2 or H, producing smaller species including molecules SiH−OH, SiH2−O, Si−H2O, and SiO and radicals SiH2−OH, SiH−H2O, HSiO, and HOSi.
02/2004;
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ABSTRACT: Experimentally, gas-phase reactions between diborane (B2H6) and carbon monoxide (CO) produce borane carbonyl (BH3CO) and a less volatile material. To elucidate the unknown part of the products, we investigated the reactions of the B2H6:CO = 1:1 system using ab initio calculations at the MP2/6-311++g** level. Within the energy range of 120 kcal/mol, we located 41 minimum and 35 transition states on the potential energy surface. Among the intermediates and products, BH2OBHCH3 is thermodynamically most stable. Its formation releases energy of 64.59 kcal/mol and requires an activation energy of 36.20 kcal/mol at the rate-limiting step. On the contrary, the initially formed BH3CO + BH3 absorbs 14.75 kcal/mol of energy and requires 19.53 kcal/mol of activation energy. The results indicate that B2H6 can act as a reducing agent to hydrogenate CO at thermal equilibrium, whereas the formation of dative complex BH3CO is kinetically favored. Theoretically, several products containing boron, hydrogen, carbon, and oxygen can be isolated.
10/2003;
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ABSTRACT: Gas-phase reactions between silane (SiH4) and ammonia (NH3) were investigated using ab initio calculations at the CCSD(T)/6-311++g**//MP2/6-31+G* level. Within the energy range of 180 kcal/mol, we located 34 equilibrium and 23 transition states on the potential energy surfaces of the Si−N−H systems. The initially weakly bonded molecular complex H3N−SiH4 eliminates the first hydrogen molecule (H2) to form the Si−N bond three ways. The first route is through a dihydrogen-bonded transition state, over a barrier of 49.31 kcal/mol, leading directly to the most stable product silylamine (H2N−SiH3). The second route is through SiH4 dissociating into SiH2 and H2, over a barrier of 57.47 kcal/mol, leading to the dative-bonded silylammonia complex H3N−SiH2. The third route is through a stepwise atomic dissociation and radical formation process, over a barrier of 131.21 kcal/mol, also leading to H3N−SiH2. With more energy, both H2N−SiH3 and H3N−SiH2 are liable to further H2 or H elimination, leading to smaller species including molecules H2N−SiH, HN−SiH2, H3N−Si, HNSi, and HSiN and radicals H2N−SiH2, H3N−SiH, H2N−Si, and NSi. Dihydrogen-bonded structures are also responsible for lowering barriers in these processes.
10/2003;
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ABSTRACT: Initial gas-phase reactions for a system containing silane (SiH4) and hydrogen (H2) were investigated using ab initio calculations at the MP2/6-311++g** level. Twenty-four minimum and 19 transition states were located on the potential energy surface of the neutral species containing one or two silicon atoms. The bonding nature of each species was elucidated by topological analyses of electron density using Bader's AIM theory. The reaction pathways were classified into three parts: Part (I) shows elimination of the first H2 and formation of disilane (Si2H6). Part (II) shows elimination of the second H2 and formation of five disilene (Si2H4) isomers. Part (III) shows elimination of the third H2 and formation of four disilyne (Si2H2) isomers. More energy is required to obtain species with less hydrogen content, and such species are more likely to be stabilized by a hydrogen bridged bond (Si−H−Si). Calculated IR spectra, dipole moments, and rotational constants were provided for comparison with the experiments.
03/2003;
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IEEE Transactions on Signal Processing 02/1993; · 2.63 Impact Factor
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ABSTRACT: The formation of charge-transfer (CT) complexes between N-methyl-6,7-methylenedioxy-tetrahydro-4-isoquinolone (MMDTIQ, the model molecule of alkaloids) and iodine monochloride has been studied with the density functional B3LYP method. The competition for ICl between n-donor(s) and π-donor in the same molecule has been compared for the first time. The results indicate that the electron-donating ability of various donor sites decreases in the following order: amino nitrogen>carbonyl oxygen>etheric oxygen≈aromatic ring. Complexes with a stoichiometry of 1:1 to 1:5 (MMDTIQ–ICl) might form. Among complexes with a given stoichiometry, the one in which the phenyl ring is involved in the binding is always the least stable. According to these results, in order to ensure an alkaloid iodinated, the amount of ICl should be far beyond that of alkaloids and a low polar solvent should be used, which is quite in agreement with our recent experimental results.
Journal of Molecular Structure THEOCHEM 686:25-30. · 1.44 Impact Factor
