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991.
992.
993.
Carroll AR Hyde E Smith J Quinn RJ Guymer G Forster PI 《The Journal of organic chemistry》2005,70(3):1096-1099
Bioassay-guided fractionation of the aqueous extract of the leaves of Alstonia actinophylla with use of a coupled enzyme assay, CPU/hippuricase, to detect carboxypeptidase U inhibitors led to the isolation of a novel indole alkaloid, actinophyllic acid (1). The structure of 1 was determined from detailed 2D NMR studies. Actinophyllic acid was found to be a potent inhibitor of the coupled enzyme assay with an IC(50) of 0.84 microM. Actinophyllic acid possesses a unique 2,3,6,7,9,13c-hexahydro-1H-1,7,8-(methanetriyloxymethano)pyrrolo[1',2':1,2]azocino[4,3-b]indole-8(5H)-carboxylic acid skeleton. 相似文献
994.
West Douglas X. Salberg Michelle M. Bain Gordon A. Liberta Anthony E. 《Transition Metal Chemistry》1997,22(2):180-184
Binuclear nickel(II) and copper(II) complexes with four 5-methoxysalicylaldehyde N(3)-substituted thiosemicarbazones and nickel(II) complexes of four 5-nitro-salicylaldehyde N(3)-substituted thiosemicarbazones have been prepared and characterized. I.r., electronic, and e.s.r. spectra of the complexes, as well as i.r., electronic, and 1H- and 13C-n.m.r spectra of the thiosemicarbazones, have been obtained. None of these compounds show significant growth inhibitory activity against the fungi Aspergillus niger and Paecilomyces variotii. 相似文献
995.
Bekkerman A Kaplan A Gordon E Tsipinyuk B Kolodney E 《The Journal of chemical physics》2004,120(23):11026-11030
C(60) (-) ions were scattered from a gold surface at impact energies of 80-900 eV. The C(n) (-) fragments abundance distribution (odd and even) and the sharp fragmentation threshold observed, point at a prompt shattering event. The measured angle and energy distributions of the C(n) (-) fragments (n=2-12) provide clear evidence for a multifragmentation process where the superheated fullerenes leave the surface "intact" and disintegrate away from the surface. 相似文献
996.
Olson RM Varganov S Gordon MS Metiu H Chretien S Piecuch P Kowalski K Kucharski SA Musial M 《Journal of the American Chemical Society》2005,127(3):1049-1052
Several levels of theory, including both Gaussian-based and plane wave density functional theory (DFT), second-order perturbation theory (MP2), and coupled cluster methods (CCSD(T)), are employed to study Au6 and Au8 clusters. All methods predict that the lowest energy isomer of Au6 is planar. For Au8, both DFT methods predict that the two lowest isomers are planar. In contrast, both MP2 and CCSD(T) predict the lowest Au8 isomers to be nonplanar. 相似文献
997.
A systematic study of the deviation from size consistency of the multireference second-order Moller-Plesset perturbation theory (MRMP2) method is presented. The size-consistency error is shown to depend on the number of monomers in a supermolecule calculation, size of basis set, number of correlated valence electrons, and size of active space. HF, F(2), and N(2) are used as test cases, with stretched bonds, to include simple, well-defined multireference character. This is essential in ensuring that MRMP2 is being tested as a multireference method. It is concluded that the MRMP2 and other multireference perturbation theory methods can exhibit significant size-consistency errors, and that the size of the error depends on the manner in which the perturbation theory is implemented. 相似文献
998.
Optically active polymer carbon nanotube composite 总被引:1,自引:0,他引:1
in het Panhuis M Sainz R Innis PC Kane-Maguire LA Benito AM Martínez MT Moulton SE Wallace GG Maser WK 《The journal of physical chemistry. B》2005,109(48):22725-22729
A completely soluble optically active polyaniline-multiwalled carbon nanotube composite was investigated by spectroscopic and microscopic techniques. It was found that the polymer's optical activity was retained in the presence of carbon nanotubes. Solutions were found to be easily processable into thin films, which exhibited dendritic structures only in the presence of nanotubes. 相似文献
999.
Results of infrared laser induced fluorescence studies on cyclopropane are presented. Molecules were excited from the ground state to the v10 level of cyclopropane using a Q-switched CO2 laser operating on either the P(14) or P(20) transition of the 9.6 μ branch. Fluorescence was observed from the v6, v8, v10 + v11 and v5 + v10 levels of cyclopropane. The self-deactivation of vibrationally excited cyclopropane through V → T/R processes was found to have a rate of 8.0 ± 1.5 ms?1 torr?1. Deactivation by rare gas collisions was also studied with comparison to simple V → T and V → R theories. V → V equilibration processes are discussed involving the v6, v8, v10, v11, and v10 + v11 levels. 相似文献
1000.
INACTIVATION OF CELL SURFACE RECEPTORS BY PHEOPHORBIDE a, A GREEN PIGMENT ISOLATED FROM Psychotria acuminata 总被引:1,自引:0,他引:1
Jan A. Glinski Eva David Thomas C. Warren Gordon Hansen Scott F. Leonard Phillip Pitner Susan Pav Rosita Arvigo M. J. Balick Eligio Panti Peter M. Grob 《Photochemistry and photobiology》1995,62(1):144-150
Abstract— The inhibition of cytokine and monoclonal antibody binding to cell surfaces caused by an extract of Psychotria acuminata, a medicinal plant used in the traditional medicine of the people of Belize (Central America), was attributed to the presence of pheophorbide a and pyropheophorbide a Since the binding of tumor necrosis factor-alpha, interleukin-8, complement factor 5a as well as epidermal growth factor to target cells was dramatically reduced, the inhibition was not receptor or cytokine specific. In addition, the respective binding of radiolabeled monoclonal antibodies CL203 and R15.7 to the cell surface antigens intracellular cell adhesion molecule-1 and lymphocyte function-associated antigen-1 ß-chain was decreased by pretreatment of cells with pheophorbide a as well. In all cases, the inhibition by pheophorbides was dependent on the simultaneous presence of light, indicating causative involvement of a photodynamic process. These observations are not unique to pheophorbides and can be extended to porphyrins as well as to other photodynamic agents. Cytotoxicity resulting from photodynamic therapy (PDT) has been documented by many studies. Our investigations suggest that the inactivation of cell surface receptors contributes not only to the antitumor effect of PDT but also to the systemic immunosuppression, a serious side effect of PDT. 相似文献