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排序方式: 共有213条查询结果,搜索用时 15 毫秒
31.
Yu. V. Knyazev A. V. Lukoyanov Yu. I. Kuz’min A. Haldar K. G. Suresh 《Optics and Spectroscopy》2014,117(3):414-418
Optical properties of two intermetallic compounds TbNi4Fe and TbNi4Co have been studied employing ellipsometry in a spectral range 0.22–15 μm to reveal their characteristic features in comparison with the parent compound TbNi5. The electronic structure of TbNi4Fe and TbNi4Co was calculated within the LSDA + U method (local spin density approximation with Hubbard U-correction). Based on the calculated electronic structure results, the theoretical optical conductivity was calculated and used to interpret experimental conductivity in the range of interband optical absorption. 相似文献
32.
Diospyros cordifolia Roxb. (Ebenaceae), commonly known as Indian ebony, is used traditionally for several medicinal purposes. In this study, the methanol extract of D. cordifolia bark (MEDC) was evaluated for its antitumour effect against Ehrlich ascites carcinoma (EAC)-bearing Swiss albino mice. Twenty-four hours after intraperitoneal inoculation of tumour (EAC) cells in mice, MEDC was administered intraperitoneally at 25 and 50?mg kg?1 bodyweight for 9 consecutive days. On the 10th day, half of the mice were sacrificed to determine the tumour volume, viable and non-viable tumour cell counts, and rest were kept alive for the assessment of median survival time and increase in life span. Haematological profiles were also determined. MEDC exhibited a marked decrease in tumour growth parameters and increased the survival rate of EAC-bearing animals. MEDC normalised the haematological parameters as compared with the EAC control mice. Therefore, this study demonstrated that D. cordifolia bark possessed remarkable antitumour efficacy. 相似文献
33.
The single crystal X-ray diffraction study of capped γ-peptide reveal that the peptide adopts helical conformation which self-assemble to form a supramolecular parallel double helical structure using intermolecular hydrogen bonding as well as π-π stacking interactions in the solid state. 相似文献
34.
P Kanoo SK Reddy G Kumari R Haldar C Narayana S Balasubramanian TK Maji 《Chemical communications (Cambridge, England)》2012,48(68):8487-8489
We herein report an unusual CO(2) adsorption behavior in a fluoro-functionalized MOF {[Zn(SiF(6))(pyz)(2)]·2MeOH}(n) (1) with a 1D channel system, which is made up of pyrazine and SiF(6)(2-) moieties. Surprisingly, desolvated 1 (1') adsorbs higher amounts of CO(2) at 298 K than at 195 K, which is in contrast to the usual trend. Combined Raman spectroscopic and theoretical studies reveal that slanted pyrazine rings in 1' with an angle of 17.2° with respect to the (200) Zn(ii)-Si plane at low temperature block the channel windows and thus reduce the uptake amount. 相似文献
35.
Marvin RG Wolford JL Kidd MJ Murphy S Ward J Que EL Mayer ML Penner-Hahn JE Haldar K O'Halloran TV 《Chemistry & biology》2012,19(6):731-741
Dynamic fluxes in the concentration of ions and small molecules are fundamental features of cell signaling, differentiation, and development. Similar roles for fluxes in transition metal concentrations are less well established. Here, we show that massive zinc fluxes are essential in the infection cycle of an intracellular eukaryotic parasite. Using single-cell quantitative imaging, we show that growth of the blood-stage Plasmodium falciparum parasite requires acquisition of 30 million zinc atoms per erythrocyte before host cell rupture, corresponding to a 400% increase in total zinc concentration. Zinc accumulates in a freely available form in parasitophorous compartments outside the food vacuole, including mitochondria. Restriction of zinc availability via small molecule treatment causes a drop in mitochondrial membrane potential and severely inhibits parasite growth. Thus, extraordinary zinc acquisition and trafficking are essential for parasite development. 相似文献
36.
Avijit Banerji Kaustabh Kumar Maiti Sunanda Haldar Chaitali Mukhopadhyay Julie Banerji Thierry Prangé Alain Neuman 《Monatshefte für Chemie / Chemical Monthly》2000,131(8):901-911
Summary. Studies on cycloadditions of C,N-diarylnitrones to cinnamic acid amides were carried out. The diastereoisomeric (I, II) and (in some cases) regioisomeric (III) cycloadducts obtained were characterized by spectroscopic and X-ray data. Conformational studies were carried out by molecular
modelling.
Received February 8, 2000. Accepted February 18, 2000 相似文献
37.
Deepta Chattapadhyay Sahabaj Mondal Santosh Kumar Dr. Debasish Haldar 《化学:亚洲杂志》2021,16(18):2723-2728
Aggregation-induced emission enhancement (AIEE) is an unusual phenomenon where luminophores show a higher photoluminescence efficiency in the aggregated and solid state. We report the design and synthesis of a series of luminophores 1 – 4 with imine functionality at 6 position of coumarin and studied their AIE propensities on self-assembly. The effect of the topology of the phenolic hydroxyl group on the emission behaviour of the luminophores has been investigated. The imines show significant solvatochromism with high emission in non-polar solvents, whereas the emission gets quenched in the polar solvent. The fluorescence in the toluene-hexane mixture arises due to the aggregation of fluorophores and falls under the category of AIEE. Not only the solution state emission of the isomeric iminocoumarin luminophores is notably varied, but also their solid-state emission found to be significantly different from each other. Moreover, the iminocoumarin 1 selectively recognizes Fe(III) over Fe(II) with a prominent color change. In situ oxidation of Fe(II) with H2O2 exhibits the same effect like Fe(III) and developed a chemical combinational logic gate. 相似文献
38.
The strong intermolecular interactions mediated by short hydrophobic sequences (e.g., 17-20, -l-Leu-l-Val-l-Phe-l-Phe-) in the middle of Aβ are known to play a crucial role in the neuropathology of Alzheimer's disease. FTIR, TEM and Congo red binding studies indicated that a series of l-Ala substituted terminally protected peptides related to the sequence 17-20 of the β-amyloid peptide, adopted β-sheet conformations. However, the Aib-modified analogues disrupt the β-sheet structure and switch over to a 310 helix with increasing number of Aib residues. X-ray crystallography shed some light on the change from sheet to helix at atomic resolution. 相似文献
39.
Ritesh Haldar Mariana Kozlowska Michael Ganschow Samrat Ghosh Marius Jakoby Hongye Chen Farhad Ghalami Weiwei Xie Shahriar Heidrich Yusuke Tsutsui Jan Freudenberg Shu Seki Ian A. Howard Bryce S. Richards Uwe H. F. Bunz Marcus Elstner Wolfgang Wenzel Christof Wll 《Chemical science》2021,12(12):4477
Charge carrier mobility is an important figure of merit to evaluate organic semiconductor (OSC) materials. In aggregated OSCs, this quantity is determined by inter-chromophoric electronic and vibrational coupling. These key parameters sensitively depend on structural properties, including the density of defects. We have employed a new type of crystalline assembly strategy to engineer the arrangement of the OSC pentacene in a structure not realized as crystals to date. Our approach is based on metal–organic frameworks (MOFs), in which suitably substituted pentacenes act as ditopic linkers and assemble into highly ordered π-stacks with long-range order. Layer-by-layer fabrication of the MOF yields arrays of electronically coupled pentacene chains, running parallel to the substrate surface. Detailed photophysical studies reveal strong, anisotropic inter-pentacene electronic coupling, leading to efficient charge delocalization. Despite a high degree of structural order and pronounced dispersion of the 1D-bands for the static arrangement, our experimental results demonstrate hopping-like charge transport with an activation energy of 64 meV dominating the band transport over a wide range of temperatures. A thorough combined quantum mechanical and molecular dynamics investigation identifies frustrated localized rotations of the pentacene cores as the reason for the breakdown of band transport and paves the way for a crystal engineering strategy of molecular OSCs that independently varies the arrangement of the molecular cores and their vibrational degrees of freedom.Pentacene assembled into 1D arrays using a metal–organic framework (MOF) approach. This cofacial packing motif, which is not present in pentacene bulk, shows an interesting interplay of band-like and hopping-type transport. 相似文献
40.
Ruthenium is extracted by benzyl alcohol from 5M LiCl containing ethyl-alpha-isonitrosoacetoacetate at pH 4-6. The extraction is quantitative if the solution is heated to boiling for 15 min. The benzyl alcohol extract shows maximum absorbance at 470 nm and at this wavelength Beer's law is obeyed over the ruthenium concentration range 0.1-1.8 mug ml . The error is 4% for 0.5 mug ml . 相似文献