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51.
52.
Turbiez M Frère P Allain M Videlot C Ackermann J Roncali J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3742-3752
Hybrid oligothiophenes based on a various combinations of thiophene and 3,4-ethylenedioxythiophene (EDOT) groups have been synthesized. UV/Vis absorption spectra show that the number and relative positions of the EDOT groups considerably affect the width of the HOMO-LUMO gap and the rigidity of the conjugated system. Analysis of the crystallographic structure of two hybrid quaterthiophenes confirms that insertion of two adjacent EDOT units in the middle of the molecule leads to a self-rigidification of the conjugated systems by intramolecular SO interactions. Cyclic voltammetry data shows that the first oxidation potential of the oligomers decreases with increasing chain length and increasing number of EDOT groups for a given chain length. Electrochemical studies and theoretical calculations show that the positions of the EDOT units in the conjugated chain control the potential difference (DeltaE(p)) between the first and second oxidation steps. Moving the EDOT groups from the outer to the inner positions of the conjugated system increases DeltaE(p). Theoretical calculations confirm that this phenomenon reflects an increase of the intramolecular coulombic repulsion between positive charges in the dication. A thin-film field-effect transistor was fabricated by vacuum sublimation of a pentamer with alternating thiophene-EDOT structure, and the hole mobility was determined. 相似文献
53.
Drahl C Cravatt BF Sorensen EJ 《Angewandte Chemie (International ed. in English)》2005,44(36):5788-5809
Researchers in the post-genome era are confronted with the daunting task of assigning structure and function to tens of thousands of encoded proteins. To realize this goal, new technologies are emerging for the analysis of protein function on a global scale, such as activity-based protein profiling (ABPP), which aims to develop active site-directed chemical probes for enzyme analysis in whole proteomes. For the pursuit of such chemical proteomic technologies, it is helpful to derive inspiration from protein-reactive natural products. Natural products use a remarkably diverse set of mechanisms to covalently modify enzymes from distinct mechanistic classes, thus providing a wellspring of chemical concepts that can be exploited for the design of active-site-directed proteomic probes. Herein, we highlight several examples of protein-reactive natural products and illustrate how their mechanisms of action have influenced and continue to shape the progression of chemical proteomic technologies like ABPP. 相似文献
54.
毒蕈碱受体激动剂的三维定量构效关系研究 总被引:1,自引:0,他引:1
采用比较分子场分析法(CoMFA)研究了55个四氢吡啶类毒蕈碱受体激动剂的三维定量构效关系(3D-QSAR), 建立了具有较强预测能力的3D-QSAR模型. 所得模型的交叉验证相关系数(q2)为0.507, 常规相关系数(R2)为0.982 , 标准方差为0.218, 说明系列化合物分子周围立体场和静电场的分布与生物活性间存在良好的相关性. 模型不仅很好地预测了训练集和测试集化合物的活性, 而且为设计活性更高的受体激动剂提供了理论依据. 相似文献
55.
56.
The three-dimensional structure of human cytochrome P450 3A4 was modeled based on crystallographic coordinates of four bacterial P450s: P450 BM-3, P450cam, P450terp, and P450eryF. The P450 3A4 sequence was aligned to those of the known proteins using a structure-based alignment of P450 BM-3, P450cam, P450terp, and P450eryF. The coordinates of the model were then calculated using a consensus strategy, and the final structure was optimized in the presence of water. The P450 3A4 model resembles P450 BM-3 the most, but the B helix is similar to that of P450eryF, which leads to an enlarged active site when compared with P450 BM-3, P450cam, and P450terp. The 3A4 residues equivalent to known substrate contact residues of the bacterial proteins and key residues of rat P450 2B1 are located in the active site or the substrate access channel. Docking of progesterone into the P450 3A4 model demonstrated that the substrate bound in a 6-orientation can interact with a number of active site residues, such as 114, 119, 301, 304, 305, 309, 370, 373, and 479, through hydrophobic interactions. The active site of the enzyme can also accommodate erythromycin, which, in addition to the residues listed for progesterone, also contacts residues 101, 104, 105, 214, 215, 217, 218, 374, and 478. The majority of 3A4 residues which interact with progesterone and/or erythromycin possess their equivalents in key residues of P450 2B enzymes, except for residues 297, 480 and 482, which do not contact either substrate in P450 3A4. The results from docking of progesterone and erythromycin into the enzyme model make it possible to pinpoint residues which may be important for 3A4 function and to target them for site-directed mutagenesis. 相似文献
57.
Summary A new equation is derived relating the retention index to the molecular polarizabilities, ionization potentials and permanent dipole moments of the stationary phase and the solute.Various implications of this equation to quantitative structure-retention relationships are discussed. 相似文献
58.
R.V. Denys V.A. Yartys Masashi Sato R.G. Delaplane 《Journal of solid state chemistry》2007,180(9):2566-2576
A new intermetallic deuteride Ce2Ni7D4.7 with an anomalous volume expansion has been studied. Its structure was solved on the basis of in situ neutron diffraction data. Expansion proceeds along the c-axis and within the CeNi2 slabs only. All D atoms are located inside these slabs and on the border between CeNi2 and CeNi5. Ordering of D atoms in the bulk of CeNi2 is accompanied by substantial deformation of these slabs thus lowering the hexagonal symmetry to orthorhombic [space group Pmcn (No. 62); a=4.9251(3) Å, b=8.4933(4) Å, c=29.773(1) Å]. Inside the CeNi2 layer the hydrogen sublattice is completely ordered; all D-D distances exceed 2.0 Å. Local coordination of Ni by D inside the CeNi2 blocks is of “open”, saddle-like type. Hydrogen ordering is mainly determined by Ce-H and H-H interactions. The pressure-composition-temperature measurements yielded the following thermodynamic parameters of the formation of the hydride: ΔH=−22.4 kJ/molH, ΔS=−59.9 J/(K molH). 相似文献
59.
60.
Vijay M. Krishnamurthy Dr. Brooks R. Bohall Chu‐Young Kim Dr. Demetri T. Moustakas Dr. David W. Christianson Prof. Dr. George M. Whitesides Prof. Dr. 《化学:亚洲杂志》2007,2(1):94-105
This paper describes a calorimetric study of the association of a series of seven fluorinated benzenesulfonamide ligands (C6HnF5?nSO2NH2) with bovine carbonic anhydrase II (BCA). Quantitative structure–activity relationships between the free energy, enthalpy, and entropy of binding and pKa and log P of the ligands allowed the evaluation of the thermodynamic parameters in terms of the two independent effects of fluorination on the ligand: its electrostatic potential and its hydrophobicity. The parameters were partitioned to the three different structural interactions between the ligand and BCA: the ZnII cofactor–sulfonamide bond (≈65 % of the free energy of binding), the hydrogen bonds between the ligand and BCA (≈10 %), and the contacts between the phenyl ring of the ligand and BCA (≈25 %). Calorimetry revealed that all of the ligands studied bind in a 1:1 stoichiometry with BCA; this result was confirmed by 19F NMR spectroscopy and X‐ray crystallography (for complexes with human carbonic anhydrase II). 相似文献