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931.
Peng Lian Wei‐Peng Lai Hua‐Qiang Cai Shaojun Qiu Bo‐Zhou Wang Jian Lv Yong‐Qiang Xue 《International journal of quantum chemistry》2011,111(14):3571-3577
Nitrosyl cation (NO+) generating reaction HONO + H+ → NO+ + H2O has been theoretically investigated by B3LYP and high‐electron‐correlation QCISD methods with 6‐31G (d,p) basis set. The solvent effects on the geometries, reaction path properties, energies, thermodynamic, and kinetic characters in four solvents (benzene, tetrahydrofuran, acetonitrile, and water) have been calculated using self‐consistent reaction field (SCRF) approach with the polarizable continuum model (PCM). The results show that the activation energy barriers and the relative energies of the products are decreased with increase of the polarities of the solvents, and the reaction is favored in polar solvents thermodynamically and kinetically. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
932.
The structural evolution of surface gratings on a glassy material is investigated by means of molecular simulations. The gratings provide a means to probe surface diffusion in the vicinity of the glass transition temperature. A theory by Mullins [J. Appl. Phys. 30, 77 (1959)] is used to extract qu-antitative measures of surface diffusivity that rely on calculation of grating amplitude as a function of time. The simulations are implemented in the context of a model binary glass mixture [S. S. Ashwin and S. Sastry, J. Phys.: Condens. Matter 15, S1253 (2003)]. We find that surface diffusion is faster than bulk diffusion by several orders of magnitude, consistent with recent experimental data for an organic glass former. The diffusivities extracted by the grating-decay approach are consistent with those estimated on the basis of mean-squared particle displacements. The grating-decay approach, however, is more efficient than traditional techniques based on Einstein's diffusion equation. Grating decay is also more versatile and is shown to be applicable in a variety of sample geometries. 相似文献
933.
934.
Recent researches shows that amino acids (AA) are not only cell signaling molecules but are also regulators of gene expression and the protein phosphorylation cascade. More precise analysis of AA composition is reckoned to be one of the most important applications in the biomedical and pharmaceutical fields. In this paper, we develop a sample, sensitive and mild method using 2-[2-(7H-dibenzo[a,g]carbazol-7-yl)-ethoxy]ethyl chloroformate (DBCEC) as A labeling reagent for AA determination by high-performance liquid chromatography (HPLC) with fluorescence detection (FLD) and identification with mass spectroscopy. The maximum excitation and emission wavelengths for DBCEC-AA derivatives were 300 and 395 nm, respectively. This method, in conjunction with a gradient elution, offered a baseline resolution of 20 AA on a reversed-phase Hypersil BDS C(18) column. LC separation for the derivatized AA showed good reproducibility, and all AA were found to give excellent linear responses with correlation coefficients > 0.9993. The calculated detection limits with a 25.0 fmol injection of each AA (at a signal-to-noise ratio of 3:1) ranged from 2.62 to 22.6 fmol. This method was applied to determine the AA composition in Saussurea involucrate and Artemisia capillaris Thunb. Meanwhile, this method exhibits a powerful potential for trace analysis of AA from biomedicine, foodstuff and other complex samples. 相似文献
935.
Xiuhui Lu Zhenxia Lian Pingping Xiang Yongqing Li 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(1):76-83
The mechanism of the cycloaddition reaction between singlet dichlorosilylene carbene (Cl2Si=C:) and formaldehyde has been investigated with MP2/6-31G* method, including geometry optimization and vibrational analysis
for the involved stationary points on the potential energy surface. The energies of the different conformations are calculated
by Zero-point energy and CCSD (T)//MP2/6-31G* method. From the potential energy profile, it can be predicted that the reaction
has two competitive dominant reaction pathways. The first dominant reaction pathway consists of two steps: (1) the two reactants
(R1, R2) firstly form a four-membered ring intermediate (INT4) through a barrier-free exothermic reaction of 387.9 kJ/mol;
(2) intermediate (INT4) then isomerizes to H-transfer product (P4.2) via a transition state (TS4.2) with energy barrier of
4.7 kJ/mol. The second dominant reaction pathway as follows: on the basis of intermediate (INT4) created between R1 and R2,
intermediate (INT4) further reacts with formaldehyde (R2) to form the intermediate (INT5) through a barrier-free exothermic
reaction of 158.3 kJ/mol. Then, intermediate (INT5) isomerizes to a silicic bis-heterocyclic product (P5) via a transition
state (TS5), for which the barrier is 40.1 kJ/mol. 相似文献
936.
Tan C Wu S Lai S Wang M Chen Y Zhou L Zhu Y Lian W Peng W Ji L Xu A 《Dalton transactions (Cambridge, England : 2003)》2011,40(34):8611-8621
Three novel Ru(II) complexes of the general formula [Ru(N-N)(2)(Norharman)(2)](SO(3)CF(3))(2), where N-N = 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), 4,7-diphenyl-1,10-phenanthroline (DIP, 3) and Norharman (9H-pyrido[3,4-b]indole) is a naturally occurring β-carboline alkaloid, have been synthesized and characterized. The molecular structures of 1 and 2 have been determined by X-ray diffraction analysis. The cellular uptake efficiencies, in vitro cytotoxicities and apoptosis-inducing properties of these complexes have been extensively explored. Notably, 1-3 exhibit potent antiproliferative activities against a panel of human cancer cell lines with IC(50) values lower than those of cisplatin. Further studies show that 1-3 can cause cell cycle arrest in the G0/G1 phase and induce apoptosis through mitochondrial dysfunction and reactive oxygen species (ROS) generation. In vitro DNA binding studies have also been conducted to provide information about the possible mechanism of action. 相似文献
937.
A general and facile approach for tailoring the multicolor output and shapes of lanthanide-ion doped fluoride upconversion nanoparticles (UCNPs) within a given composition is presented. By adjusting the temperature and time in the thermolysis procedure, the color output and shapes of NaYF(4):20%Yb, 2%Er UCNPs can be readily manipulated. The nanoparticles were characterized through the use of transmission electron microscopy (TEM), powder X-ray diffraction (XRD) and upconversion luminescence spectroscopy. It is shown that the relative intensities of green emissions gradually increased with the rise of temperature and prolongation of growth time under excitation of 980 nm, which resulted in multicolor output of NaYF(4):20%Yb, 2%Er UCNPs. Simultaneously, the shapes for UCNPs can also be controlled. TEM images, estimated micro-stress by Williamson-Hall methodology and a series of control experiments and analyses reveal that crystallinity is mainly responsible for the multicolor output of UCNPs. Based on the above method, the tailoring of color output is also successfully realized in Ho(3+) and Tm(3+) ions. It is expected that this method may be used to tune the physical properties of other nanoparticles, and these multicolored UCNPs are promising for applications in multiplexed bioimaging, biodetection, display, other optical technologies, etc. 相似文献
938.
Lian P Wei H Zheng C Nie Y Bian J Bian Z Huang C 《Dalton transactions (Cambridge, England : 2003)》2011,40(20):5476-5482
Two novel iridium(III) complexes, [Ir(dfppy)(2)(pmc)] and [Ir(ppy)(2)(pmc)] (dfppy = 2-(4',6'-difluoro-phenyl)pyridine, ppy = 1-phenyl-pyridine), were designed and synthesized using 2-carboxyl-pyrimidine (Hpmc) as an ancillary ligand. Single crystals were obtained and characterized by single crystal X-ray diffraction. The tetrametallic complexes {[(C^N)(2)Ir(μ-pmc)](3)EuCl(3)} (C^N = dfppy, ppy) were synthesized using the iridium(III) complexes as "ligands". Photophysical and theoretical studies indicate that [Ir(dfppy)(2)(pmc)] is more suitable for sensitizing the emission of Eu(III) ions than [Ir(ppy)(2)(pmc)]. 相似文献
939.
Ravidomycin V and related compounds, e.g., FE35A-B, exhibit potent anticancer activities against various cancer cell lines in the presence of visible light. The amino sugar moieties (D-ravidosamine and its analogues, respectively) in these molecules contribute to the higher potencies of ravidomycin and analogues when compared to closely related compounds with neutral or branched sugars. Within the ravidomycin V biosynthetic gene cluster, five putative genes encoding NDP-D-ravidosamine biosynthetic enzymes were identified. Through the activities of the isolated enzymes in vitro, it is demonstrated that ravD, ravE, ravIM, ravAMT and ravNMT encode TDP-D-glucose synthase, TDP-4-keto-6-deoxy-D-glucose-4,6-dehydratase, TDP-4-keto-6-deoxy-D-glucose-3,4-ketoisomerase, TDP-3-keto-6-deoxy-D-galactose-3-aminotransferase, and TDP-3-amino-3,6-dideoxy-D-galactose-N,N-dimethyl-transferase, respectively. A protocol for a one-pot enzymatic synthesis of TDP-D-ravidosamine has been developed. The results presented here now set the stage to produce TDP-D-ravidosamine routinely for glycosylation studies. 相似文献
940.
The formation of 3,6-di-O-acetyl-1,2,4-O-orthoacetyl-α-D-glucopyranose was observed in the gold(I)-catalyzed glycosidation of peracetyl glucopyranosyl ortho-hexynylbenzoate; experiments with substrates bearing deuterium labeled 2-O-acetyl or 4-O-acetyl groups indicated that the orthoacetate was derived from the 4-O-acetyl group, which provided a direct evidence for the remote participation of the 4-O-acyl group in glycosylation. 相似文献