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251.
The effects of four factors (different side chains, side-chain disorder, conformational change, and ions and water) on the energy band structures of proteins have been investigated with the aid of the CNDO/2 crystal orbital method. The results indicate that these factors are very important. The consequences of these effects on the semiconductive properties of proteins are discussed. 相似文献
252.
Lizeng PengHuawei Liu Tao ZhangFengzhi Zhang Tiansheng MeiYi Li Yulin Li 《Tetrahedron letters》2003,44(27):5107-5108
A stereoselective synthesis of brassinolide, which involves construction of the side chain by a highly stereoselective aldol reaction between 20S-6β-methoxy-3α,5-cyclo-5α-pregnane-20-carboxaldehyde 2 and ketone 3 or 4 catalyzed by l-proline, is described. 相似文献
253.
Studies of the electrochemical behavior of epinephrine at a homocysteine self-assembled electrode 总被引:6,自引:0,他引:6
The self-assembled electrode with the homocysteine monolayer (Hcy/Au) has been characterized by infrared spectroscopy and ac impedance spectroscopy in electrolyte. The Hcy/Au electrode is demonstrated to promote the electrochemical response of epinephrine (E) by cyclic voltammetry. A pair of well-defined redox waves was obtained and the calculated standard rate constant (ks) is 2.1×10−2 cm s−1 at the self-assembled electrode. The reduction peak of E can be used to determine the concentration of E in presence of ascorbic acid (AA) owing to the Hcy/Au also promoting the electrochemical oxidation of AA. 相似文献
254.
Rong Chen Yu-Hui Cheng Lei Liu Xiao-Song Li Qing-Xiang Guo 《Research on Chemical Intermediates》2002,28(1):41-48
MP2/6-31+G* calculations were performed on the cation- complexes of ethylene, cyclobutadiene and benzene with a number of atomic cations. It was found that except B+ all the atomic cations form -type cation- complexes with ethylene. On the other hand, with cyclobutadiene Li+, N+, Na+, P+ and K+ form -type complexes, whereas H+, F+, and Cl+ form covalent -type complexes. With benzene Li+, B+, Na+, Al+, and K+ form -type complexes whereas H+, F+, and Cl+ form -type complexes. It was concluded that the driving force to form the -type complex is chemical bonding, and that for metal cations to form -type complexes is non-covalent interaction. 相似文献
255.
Zhang X 《Journal of colloid and interface science》1999,212(1):107-122
This paper presents a numerical study of the dynamics of a viscous liquid drop that is being formed directly at the tip of a vertical tube into ambient air. A model is developed to predict the evolution of the drop shape and its breakup based on RIPPLE, which is a solution algorithm for computing transient, two-dimensional, incompressible fluid flow with surface tension on free surfaces of general topology (D. B. Kothe and R. C. Mjolsness, AIAA J. 30, 2694 (1992)). The full Navier-Stokes system is solved by using finite-difference formulation on a Eulerian mesh. The mesh is fixed in space, with the flow and surface moving through it to ensure accurate calculations of complex free surface flows and topology, including surface breakup and coalescence. The novel feature of the numerical algorithm is the use of a Eulerian volume-tracking approach which allows the calculations to pass the breaking point during formation of a drop continuously without interruption or numerical modification and, therefore, to explore the features of generation of satellite droplets. The effects of physical and geometric parameters on the nonlinear dynamics of drop growth and breakup are investigated. The focus here is on drop breakup and subsequent formation of satellite droplets. The effects of finite inertial, capillary, viscous, and gravitational forces are all accounted for to classify different formation dynamics and to elucidate features of satellite droplet generation. The numerical predictions are compared with experimental measurements for water drops, and the results show good agreement. Copyright 1999 Academic Press. 相似文献
256.
257.
Qian-Feng Zhang Yu-Jie Liu Richard D. Adams Alexander Rothenberger Dieter Fenske Wa-Hung Leung 《Journal of Cluster Science》2006,17(3):445-455
Treatment of tetracopper(I)-phosphonitocavitand [1·Cu4(μ-Cl)4(μ4-Cl)] (2) (1 = tetraphosphonitocavitand [rccc-2,8,14,20-tetrakis-(iso-butyl)-phosphonitocavitand (C44H48O8P4Ph4)]) with PhSeSiMe3 in THF at low temperature afforded a novel polyanionic cluster [pyH]6[(CuCl)9(μ3-SePh)5(μ4-SePh)] (4) as a major product along with a new tetracopper(I)-phosphonitocavitand (3) with a centered μ3-Cl. Molecular structure of anionic cluster in 4 consists of six PhSe− bridging ligands containing five μ3-SePh and one exceptional μ4-SePh bridging nine copper atoms, of which eight copper atoms have trigonal coordination geometry and the other has distorted
tetrahedral geometry.
Dedicated to Professor Han-Qin Liu on the occasion of his 70th birthday. 相似文献
258.
Yechen Hu Zhongcheng Wang Liang Liu Jianhua Zhu Dongxue Zhang Mengying Xu Yuanyuan Zhang Feifei Xu Yun Chen 《Chemical science》2021,12(23):7993
Precision medicine has been strongly promoted in recent years. It is used in clinical management for classifying diseases at the molecular level and for selecting the most appropriate drugs or treatments to maximize efficacy and minimize adverse effects. In precision medicine, an in-depth molecular understanding of diseases is of great importance. Therefore, in the last few years, much attention has been given to translating data generated at the molecular level into clinically relevant information. However, current developments in this field lack orderly implementation. For example, high-quality chemical research is not well integrated into clinical practice, especially in the early phase, leading to a lack of understanding in the clinic of the chemistry underlying diseases. In recent years, mass spectrometry (MS) has enabled significant innovations and advances in chemical research. As reported, this technique has shown promise in chemical mapping and profiling for answering “what”, “where”, “how many” and “whose” chemicals underlie the clinical phenotypes, which are assessed by biochemical profiling, MS imaging, molecular targeting and probing, biomarker grading disease classification, etc. These features can potentially enhance the precision of disease diagnosis, monitoring and treatment and thus further transform medicine. For instance, comprehensive MS-based biochemical profiling of ovarian tumors was performed, and the results revealed a number of molecular insights into the pathways and processes that drive ovarian cancer biology and the ways that these pathways are altered in correspondence with clinical phenotypes. Another study demonstrated that quantitative biomarker mapping can be predictive of responses to immunotherapy and of survival in the supposedly homogeneous group of breast cancer patients, allowing for stratification of patients. In this context, our article attempts to provide an overview of MS-based chemical mapping and profiling, and a perspective on their clinical utility to improve the molecular understanding of diseases for advancing precision medicine.An overview of MS-based chemical mapping and profiling, indicating its contributions to the molecular understanding of diseases in precision medicine by answering "what", "where", "how many" and "whose” chemicals underlying clinical phenotypes. 相似文献
259.
Highly ordered mesoporous silica can be regenerated from a mesoporous carbon CMK-3 that is a negative replica of mesoporous silica SBA-15, indicating reversible replication between carbon and inorganic materials. 相似文献
260.
The direct reactions of (C5H5)2LnCl with LiN=C(NMe2)2 proceeded at room temperature in THF under pure nitrogen to yield the lanthanocene guanidinate complexes [(C5H5)2Ln(mu-eta1:eta2-N=C(NMe2)2)]2 (Ln = Gd (1), Er (2)). Treatment of phenyl isocyanate with complexes 1 and 2 results in monoinsertion of phenyl isocyanate into the Ln-N(mu-Gua) bond to yield the corresponding insertion products [(C5H5)2Ln(mu-eta1:eta2-OC(N=C(NMe2)2)NPh)]2 (Ln = Gd (3), Er (4)), presenting the first example of unsaturated organic small molecule insertion into the metal-guanidinate ligand bond. Further investigations indicate that N,N'-diisopropylcarbodiimide does not react with complexes 1 and 2 under the same conditions; however, it readily inserts into the lithium-guanidinate ligand bond of LiN=C(NMe2)2. As a synthon of the insertion product Li[(iPrN)2C(N=C(NMe2)2)], its reaction with (C5H5)2LnCl gives the novel organolanthanide complexes containing the guanidinoacetamidinate ligand, (C5H5)2Ln[(iPrN)2C(N=C(NMe2)2)] (Ln = Yb (5), Er (6), Dy (7)). All complexes were characterized by elemental analysis and spectroscopic properties. The structures of complexes 1, 3, 5 and 7 were determined through X-ray single-crystal diffraction analysis. 相似文献