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991.
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
992.
Hui Yang Xing Chen Guoxiang Hu Wan-Ting Chen Siobhan J. Bradley Weijie Zhang Gaurav Verma Thomas Nann De-en Jiang Paul E. Kruger Xiangke Wang He Tian Geoffrey I. N. Waterhouse Shane G. Telfer Shengqian Ma 《Chemical science》2020,11(13):3523
Optimizing interfacial contacts and thus electron transfer phenomena in heterogeneous electrocatalysts is an effective approach for enhancing electrocatalytic performance. Herein, we successfully synthesized ultrafine β-Mo2C nanoparticles confined within hollow capsules of nitrogen-doped porous carbon (β-Mo2C@NPCC) and found that the surface layer of molybdenum atoms was further oxidized to a single Mo–O surface layer, thus producing intimate O–Mo–C interfaces. An arsenal of complementary technologies, including XPS, atomic-resolution HAADF-STEM, and XAS analysis clearly reveals the existence of O–Mo–C interfaces for these surface-engineered ultrafine nanostructures. The β-Mo2C@NPCC electrocatalyst exhibited excellent electrocatalytic activity for the hydrogen evolution reaction (HER) in water. Theoretical studies indicate that the highly accessible ultrathin O–Mo–C interfaces serving as the active sites are crucial to the HER performance and underpinned the outstanding electrocatalytic performance of β-Mo2C@NPCC. This proof-of-concept study opens a new avenue for the fabrication of highly efficient catalysts for HER and other applications, whilst further demonstrating the importance of exposed interfaces and interfacial contacts in efficient electrocatalysis.Ultrafine β-Mo2C nanostructures encapsulated in N-doped carbon capsules featuring O–Mo–C interfaces as the active sites for HER have been unveiled. 相似文献
993.
Electrocatalytic oxidation of thiosulfate on a modified nickel hexacyanoferrate film electrode 总被引:1,自引:0,他引:1
Xingyao Zhou Shengfu Wang Zhengpin Wang Mian Jiang 《Fresenius' Journal of Analytical Chemistry》1993,345(6):424-427
Summary A modified nickel hexacyanoferrate film glassy carbon electrode is prepared by the electrochemical deposition technique. The film is very stable upon voltammetric scanning in the potential range of 1.0 to –0.5 V (vs. SCE) and an oxidation peak occurs at 0.35 V (vs. SCE) (1 mol/l NaNO3). The effects of electrolyte, solvent, coexisting ions and other variables on the voltammetric behaviour of the modified film have been studied. The thickness of the resulting film can be controlled by changing the number of voltammetric cycles and the concentrations of nickel(II) and hexacyanoferrate(III) ions. The film shows catalytic activity towards electrooxidation of thiosulfate with a peak potential +0.5 V (K–-containing media). This oxidation potential of thiosulfate on the modified electrode is shifted negatively by about 550 mV as compared to the naked glassy carbon electrode. For practical application, the modified electrode can be used for the determination of thiosulfate in concentrations from 5.0×10–5 to 1.0×10–1 mol/l. This method has been successfully applied to the determination of thiosulfate in photographic waste effluents. 相似文献
994.
Two novel copper(I) complexes with Cu‐O bonds, [Cu2L2(PPh3)2](BF4)2 ( 1 ) and [Cu(L)(dppeo)](BF4) ( 2 ) ( L = 6‐(4‐diethylmethylphosphonatephenyl)‐2,2′‐bipyridine, dppeo = bis(diphenylphosphino)ethane monoxide), have been prepared and their structures characterized. In the binuclear complex 1 , the ligand L serves as tridentate donor with the N, N′ and O as coordination atoms, and the two CuI atoms are bridged through both P = O donor atoms in different ligand L with a triphenylphosphine molecule as auxiliary ligand. While in mononuclear complex 2 , both ligands L and dppeo behave as bidentate with N∧N from L and P∧O from dppeo chelating to CuI atom. 相似文献
995.
Jürgen Pebler Klaus Schmidt Kurt Dehnicke Prof. Dr. Johann Weidlein 《无机化学与普通化学杂志》1978,440(1):269-277
121Sb Mössbauer Spectra of Antimony (V) Compounds. II The Mössbauer resonance effect of 121Sb has been studied at 4.2 K in a series of 11 antimony(V) compounds which are in most cases bridged. Isomer shift and quadrupole splitting variations are considered in the light of results of X-ray and vibrational spectroscopy. Preparation and the vibrational spectra of [NMe4][SbCl4(n3)2] are described. Within the limitations of available structural data related tin compounds are compared with those of corresponding 119Sn Mössbauer spectra. 相似文献
996.
Prof. Dr. W. Kratz 《Monatshefte für Mathematik》1981,91(4):275-289
Given semi-normsf andg on
n
and a real number >0. Then the successive minima off under the constraintg are defined by
j
: = inf {: there existj linear independent vectors inZ
n
withf andg}. The main theorem of this paper (Lagrange multiplier theorem) states that the successive minima of a certainnorm h on
n
(without constraints) coincide with the
j
's up to bounded factors. Moreover, this norm is constructed explicitly. Using Minkowski's wellknown theorem on successive minima and our result certain inequalities on simultaneous Diophantine approximations are derived. 相似文献
997.
998.
Masaki Shimizu Prof. Dr. Takuya Kurahashi Dr. Katsuhiro Shimono Dr. Kei Tanaka Ikuhiro Nagao Shin‐ichi Kiyomoto Tamejiro Hiyama Prof. Dr. 《化学:亚洲杂志》2007,2(11):1400-1408
Treatment of 1,1‐bis(pinacolatoboryl)ethene with an excess of 1‐bromo‐1‐lithioethene gave 2,3‐bis(pinacolatoboryl)‐1,3‐butadiene in high yield. Palladium‐catalyzed cross‐coupling of the resulting diborylbutadiene with aryl iodides took place smoothly in the presence of a catalytic amount of Pd(OAc)2/PPh3 and aqueous KOH to give 2,3‐diaryl‐1,3‐butadienes in good yields. The coupling reaction with commercially available 4‐acetoxyphenylmethyl chloride under the same conditions followed by hydrolysis of the acetyl groups gave anolignan B in a one‐pot manner. A variety of [3]‐ to [6]dendralenes were synthesized by palladium‐catalyzed coupling of the diene or 1,1‐bis(pinacolato)borylethene with alkenyl or dienyl halides, respectively, in good yields. 相似文献
999.
(Me2NH2)[(Ph3Sn)3(MoO4)2], a Triorganotin Molybdate with Layer Structure The reaction of [(Ph3Sn)2MoO4] with (Me2NH2)Cl in an acetonitrile/water mixture leads to the formation of (Me2NH2)[(Ph3Sn)3(MoO4)2] ( 1 ). ( 1 ) crystallizes in the space group Pca21 with a = 1967.0(4), b = 1353.1(2) and c = 2176.6(5) pm. In the crystal structure of 1 Ph3SnO2 bipyramides and MoO4 tetrahedra are linked by corner sharing to give a layer structure. Additionally the layers are connected by O···H···N hydrogen bridges between MoO4 groups and [Me2NH2]+ ions to give a 3D network structure. 相似文献
1000.
Chao Song Dan Gao Tianying Yuan Yongli Chen Liping Liu Xiaowu Chen Yuyang Jiang 《中国化学快报》2019,30(5):1038-1042
Cell migration and invasion are critical steps in cancer metastasis, which are the major cause of death in cancer patients. Tumor-associated macrophages(TAMs) and interstitial flow(IF) are two important biochemical and biomechanical cues in tumor microenvironment, play essential roles in tumor progression. However, their combined effects on tumor cell migration and invasion as well as molecular mechanism remains largely unknown. In this work, we developed a microfluidic-based 3 D breast cancer model by co-culturing tumor aggregates, macrophages, monocytes and endothelial cells within 3 D extracellular matrix in the presence of IF to study tumor cell migration and invasion. On the established platform, we can precisely control the parameters related to tumor microenvironment and observe cellular responses and interactions in real-time. When co-culture of U937 with human umbilical vein endothelial cells(HUVECs) or MDA-MB-231 cells and tri-culture of U937 with HUVECs and MDA-MB-231 cells, we found that mesenchymal-like MDA-MB-231 aggregates activated the monocytes to TAM-like phenotype macrophages. MDA-MB-231 cells and IF simultaneously enhanced the macrophages activation by the stimulation of colony-stimulating factor 1(CSF-1). The activated macrophages and IF further promoted vascular sprouting via vascular endothelial growth factor(VEGFα) signal and tumor cell invasion. This is the first attempt to study the interaction between macrophages and breast cancer cells under IF condition. Taken together, our results provide a new insight to reveal the important physiological and pathological processes of macrophages-tumor communication. Moreover, our established platform with a more mimetic 3 D breast cancer model has the potential for drug screening with more accurate results. 相似文献