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排序方式: 共有366条查询结果,搜索用时 8 毫秒
81.
Aimée Tomlinson Brian Frezza Matthew Kofke Miaomiao Wang Bruce A. Armitage David Yaron 《Chemical physics》2006
3,3-Diethylthiadicarbocyanine (DiSC2(5)) is a monocationic dye which forms cofacial dimers that insert into the minor groove of DNA [J. Seifert, R. Conner, S. Kushon, M. Wang, B. Armitage, J. Am. Chem. Soc. 121 (1999) 2987]. These dyes self-assemble into long helical aggregates in AT-rich regions with the dimers aligned in an end-to-end fashion. A model is presented that allows for the construction of large helical aggregates with continuously variable structural parameters. The spectra or excited states are computed using a direct intermediate neglect of differential overlap (INDO) single configuration interaction (SCI) method. Results are reported for both H- and J-type aggregates ranging in size from 2 to 6 dimers. A more approximate model based on transition charge densities enables calculations of larger aggregates. These models are used to derive structural parameters of both H- and J-type aggregates from the available spectral data, resulting in a new structural model for J-type aggregation in these systems. 相似文献
82.
In this note a method is presented for quick implementation of configuration interaction (CI) calculations in molecules. A
spin-free Hamiltonian for anN electron system in a spin stateS, expressed in terms of the generators for the unitary group algebra, is diagonalized over orbital configurations forming
a basis for the irreducible representation [21/2N-S
12S
] of the permutation group S
N
. It has been found that the basic algebraic expressions necessary for the CI calculation involve a limited category of permutations.
These have been displayed explicitly.
On leave from the Indian Institute of Technology, Bombay, India. 相似文献
83.
Alexei N. Pankratov Inna M. Uchaeva 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):791-802
By the PM3 method, standard values of entropy, heats and Gibbs energies of formation and dipole moments of the molecules have been computed for a series of inorganic and organic antimony compounds. Linear dependences P exper = bP theor (where P is any of the mentioned properties) have been stated, allowing a priori evaluation of thermodynamic characteristics and molecular dipole moments of Sb-containing substances. It has been concluded that triphenylstibinedichloride in benzene solution, as well as triphenylstibinehydroxychloride in dioxane medium, exist in the form of trigonal bipyramid with two axial chlorine and oxygen atoms. 相似文献
84.
The first lanthanide (III) mediated α′-alkylation of MVK with aldehydes is described. This methodology allows the efficient preparation of a number of synthetically important hydroxyenones. 相似文献
85.
Chiral bis(oxazoline) complexes of Cu(II), Zn(II) and Mg(II) have been immobilized on silica support via hydrogen-bonding interactions. Up to 93% ee is obtained in the Diels-Alder reaction between 3-((E)-2-butenoyl)-1,3-oxazolin-2-one and cyclopentadiene at room temperature with the heterogeneous bis(oxazoline) complexes, and the catalysts can be recycled without losing enantioselectivity. Experimental and theoretical studies show that the reversal of the absolute product configuration upon immobilization of the PhBOX-Cu(II) catalyst is triggered by the anion dissociation from Cu(II) onto the surface of the support. 相似文献
86.
采用分子动力学模拟对不同温度下磷酸二氢铵水溶液的构型能和径向分布函数进行了研究.磷酸二氢根被看作七节点模型,铵离子被看作五节点模型,而水分子则被看作简单点电荷模型.在饱和温度附近,体系局域粒子数密度有波动.373-400K的溶液势能增长缓慢表明磷酸二氧铵部分分解.磷酸二氢根中的氧原子与铵离子中氢原子的径向分布函数在三种不同温度下呈现明显不同,表明溶液中平均氢键数目随温度的变化明显改变.温度对磷酸二氢根中的氧原子和氧原子的结合有一定的影响,而在饱和溶液中有更多的生长基无产生. 相似文献
87.
四氢β-咔啉类化合物的13C NMR研究 总被引:1,自引:1,他引:1
测定了四对新合成的四氢β-咔啉化合物的13C NMR谱,通过APT、HETCOR和HETCOLOC谱指认了所有碳的归属.所确定的化学位移规律可以用来确定它们的构型. 相似文献
88.
Na Lin Heng Li Jian-Rong Wang Wei Tang Ming-Yue Zheng Hong Wang Cheng-Shi Jiang Yue-Wei Guo 《中国化学》2022,40(1):28-38
In the present study,nine new cembrane-type diterpenoids,namely ximaonanolobatins A—I(1—9),together with six related known analogs(10—15)and four known tetraprenylated alkaloids malonganenones D,E,H,and K(16—19)were isolated from the soft coral Sinularia nanolobata collected off the Ximao Island in the South China Sea.The structures of 1—9 were robustly established by a combination of detailed spectroscopic analyses,chemical reactions,quantum mechanical(QM)-NMR methods,biogenetic consideration,and the comparison with those literature data.The absolute configuration of 1 was confirmed by X-ray diffraction analysis,and the absolute configuration of 2 was determined by QM-NMR calculations and chemical transformation.In addition,the absolute configuration of 3 was determined using the modified Mosher's method.All these isolates were evaluated for their anti-inflammatory and anti-tumor activities.The results showed that only compound 15 exhibited potential anti-inflammatory effect against LPS-induced TNF-αrelease in RAW264.7 macrophages with an IC50 value of 12.6μmol/L. 相似文献
89.
11-氯代青蒿素的合成及其构型的确定陆德文,李英(中国科学院上海药物研究所,上海,200031)关键词11-氯代青蒿素,合成,构型青蒿素(Artemisinin,QHS)是从中药青蒿中分离到的一种含过氧基团的新型倍半萜内酯,具有强抗疟作用。它的结构测... 相似文献
90.
Noncentral elliptical configuration density 总被引:1,自引:0,他引:1
Francisco J. Caro-Lopera Jos A. Díaz-García Graciela Gonzlez-Farías 《Journal of multivariate analysis》2010,101(1):32-43
The noncentral configuration density, derived under an elliptical model, generalizes and corrects the Gaussian configuration and some Pearson results. Partition theory is then used to obtain explicit configuration densities associated with matrix variate symmetric Kotz type distributions (including the normal distribution), matrix variate Pearson type VII distributions (including t and Cauchy distributions), the matrix variate symmetric Bessel distribution (including the Laplace distribution) and the matrix variate symmetric Jensen-logistic distribution. 相似文献