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91.
Two optically active steroid CD ring synthons 4 and 19 were synthesized from 11 obtained by the microbial asymmetric reduction of a pro-chiral trione 10 which could be efficiently prepared by the reaction of a new annelating reagent 9 with 2-ethyl-cyclopentane-1, 3-dione. 相似文献
92.
In the presence of a Lewis acid the phenol-Passerini three-component reaction (phenol-P-3CR) system is found to deliver a product of the phenol-Ugi four-component reaction (phenol-U-4CR). It is the first demonstration of an isocyanide as an amine equivalent in isocyanide-based multicomponent reactions (IMCRs). In general, by using Ti(O-i-Pr)4 in MeOH both phenol-U-4CR and U-4CR products are synthesized from an aromatic aldehyde, a phenolic or carboxylic acid, and an isocyanide. Moreover, by using MeCN as the solvent, the phenol-P-3CR products can be obtained in good yields without contamination of the phenol-U-4CR products. 相似文献
93.
94.
The electrical transport and magnetic properties of BaVS3, made up of individual VS3 octahedral chains, were examined on the basis of first principles and tight-binding electronic structure calculations. The electrical conductivity of BaVS3 is nearly isotropic despite its one-dimensional structural feature, because of the orbital interactions associated with the short S···S contacts within each VS3 chain and between adjacent VS3 chains. The probable cause for the metal-insulator transition at ∼70 K was examined in terms of first principles electronic structure calculations, which indicate that the metallic and magnetic insulating states of BaVS3 are nearly the same in energy. This is consistent with the observation that the metal-insulator transition at ∼70 K is caused by electron localization. The observed magnetic properties of BaVS3 below ∼70 K are readily explained under the assumption that the symmetry-broken t2g-orbitals act as the magnetic orbitals in the magnetic insulating state of BaVS3. The probable cause for the latter was discussed. 相似文献
95.
Dai QH Tommos C Fuentes EJ Blomberg MR Dutton PL Wand AJ 《Journal of the American Chemical Society》2002,124(37):10952-10953
The use of side chains as catalytic cofactors for protein mediated redox chemistry raises significant mechanistic issues as to how these amino acids are activated toward radical chemistry in a controlled manner. De novo protein design has been used to examine the structural basis for the creation and maintenance of a tryptophanyl radical in a three-helix bundle protein maquette. Here we report the detailed structural analysis of the protein by multidimensional NMR methods. An interesting feature of the structure is an apparent pi-cation interaction involving the sole tryptophan and a lysine side chain. Hybrid density functional calculations support the notion that this interaction raises the reduction potential of the W degrees /WH redox pair and helps explain the redox characteristics of the protein. This model protein system therefore provides a powerful model for exploring the structural basis for controlled radical chemistry in protein. 相似文献
96.
Cardiolipin is an important phospholipid present in the mitochondrial inner membrane. It plays a key function in mitochondrial respiration by interacting with many enzymes or cofactors related to oxidative phosphorylation complexes. We have determined the concentration of cardiolipin using on-line 10-N-nonyl acridine orange (NAO) dye interaction capillary electrophoresis (CE) and spectrophotometric detection with a sample throughput of 3 min. In addition to the presence of 0.1 mM NAO, the background electrolyte (BGE) composition has been set at 80% methanol-10% acetonitrile-10% H(2)O (all v/v) to provide both good solubility and the maximum absorbance enhancement at 497 nm for the NAO-cardiolipin complex as compared to NAO alone. Sample consumption for each injection is about 57 nL. A calibration curve is established from 0.5 microM to 0.1 mM with R (2) = 0.9912 with a detection limit of 0.05 microM for cardiolipin. In a blind study, actual mitochondrial cell membrane samples in the microL range before or after UV light exposure were analyzed using the CE method. Cardiolipin concentration decreased in the different parts of the membrane sample upon UV photolysis of the cells. Support for the theory that UV light can induce cardiolipin translocation from the inner membrane (IM) to the outer membrane (OM) was indicated by a significant percentage increase of cardiolipin (as measured by the cardiolipin in the OM as compared to the sum total in the OM and IM) from 30.7 +/- 2.4% before UV light photolysis to 38.3 +/- 2.2% after UV irradiation. 相似文献
97.
98.
The adsorption of (R)- and (S)-2-phenylpropionamide (PPA, C(9)H(11)ON) molecules on a Cu(111) surface has been investigated using the density functional method with supercell models. The adsorption orientations of both (R)- and (S)-PPA molecules on the surface are the same: the phenyl rings are approximately parallel to the Cu(111) surface and positioned in the hollow sites, the amino and methyl groups occupy two-bridge sites, and the carbonyl occupies the top site. After the adsorption, the bond lengths in the two enantiomers are almost unchanged, but the changes for two dihedral angles show differences, especially for (R)-PPA molecule. The first angles between the (N,C9,C7) plane and the (C9,C7,C6) plane are 19.4 and 0.7 degrees for (R)- and (S)-PPA molecules, respectively, and the second angles between the (C8,C7,C6) plane and the (C7,C6,C5) plane are 74.8 and 0.4 degrees for (R)- and (S)-PPA molecules, respectively. The adsorption energies of (R)- and (S)-PPA molecules are calculated to be -34 and -26 kJ mol(-1), respectively. The simulated scanning tunneling microscopy (STM) images of (R)- and (S)-PPA molecules on the Cu(111) surface display different features and are coincident with the experimental ones. The interaction between the adsorption molecule and the metal surface is found to be responsible for the discrimination of (R)- and (S)-PPA molecules on the surface. 相似文献
99.
The coordination compound [Co(C10H7COO)2(H2O)3]2n
· 4nH2O was prepared by the reaction of 1-naphthoic acid and cobalt(II) acetate tetrahydrate in basic solution, and was fully characterized
by X-ray diffraction, element analysis, FTIR, TG-DTA and luminescent spectra. In the crystal the six-coordinated Co(II) centers
are linked into one-dimensional zigzag chains by water molecules, which are further assembled into a two-dimensional network through weak inter-chain C–H···π interactions.
The solid complex exhibits favorable fluorescent properties similar to those of free ligand at room temperature, which can
be assigned to the intraligand electronic transfer. 相似文献
100.
Shu-guang Yang Yong-jun Zhang Xin-hua Dai Wen-hong Tang Chun-yan Liu Wei-xiao Cao Yu-liang Li Jian Xu State Key Laboratory of Polymer Physics Chemistry Institute of Chemistry Chinese Academy of Sciences Beijing China Technology Institute of Physics Chemistry Chinese Academy of Sciences Beijing China College of Chemistry Molecular Engineering Peking University Beijing China 《高分子科学》2002,(6):591-593
Electrostatic layer-by-layer self-assembly multilayer films were successfully fabricated from C_(60)-ethylenediamineadduct (C_(60)-EDA) and DNA. Under visible light irradiation, DNA is ready to be cleaved and the films are destroyed. 相似文献