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191.
Dr. Pravat Mondal Dr. Ephrath Solel Dr. Natalia Fridman Prof. Ehud Keinan Prof. Ofer Reany 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(58):13336-13343
Bambusurils (BUs) are known to be rigid cavitands that feature an extended, jigger-like conformation, and the BU[6]s strongly bind anions within their hydrophobic cavity. These features are not necessarily shared by the family of perthio-BUs. This study reveals that perthio-BUs assume a compact conformation and perthio-BU[6]s are poor anion binders, crystallizing as anion-free species from solutions containing halide salts. Computational studies show that the equatorial sulfur atoms compete against guest anions for binding with the glycoluril methine groups via strong van der Waals (vdW) attractive interactions. These competitive contacts not only account for the diminished anion-binding of perthio-BUs, but also explain their compact conformation. The semithio- and perthio-BU[4]s form linear coordination polymers with HgII in the solid-state regardless of their intrinsic molecular conformation. The strong involvement of sulfur atoms in intramolecular interactions differentiates the equatorial from the axial (peripheral) heteroatoms, thus offering chemoselective and regioselective transformations. 相似文献
192.
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194.
We briefly review the concepts of almost causality and the conditions under which space-time is reflecting and distinguishing. We propose some relations between these conditions and also prove the propositions using a constructive approach. 相似文献
195.
Reversible Photoswitching of RNA Hybridization at Room Temperature with an Azobenzene C‐Nucleoside
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Thomas Goldau Keiji Murayama Dr. Clara Brieke Sabrina Steinwand Dr. Padmabati Mondal Dr. Mithun Biswas Prof. Dr. Irene Burghardt Prof. Dr. Josef Wachtveitl Prof. Dr. Hiroyuki Asanuma Prof. Dr. Alexander Heckel 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2845-2854
Photoregulation of RNA remains a challenging task as the introduction of a photoswitch entails changes in the shape and the stability of the duplex that strongly depend on the chosen linker strategy. Herein, the influence of a novel nucleosidic linker moiety on the photoregulation efficiency of azobenzene is investigated. To this purpose, two azobenzene C‐nucleosides were stereoselectively synthesized, characterized, and incorporated into RNA oligonucleotides. Spectroscopic characterization revealed a reversible and fast switching process, even at 20 °C, and a high thermal stability of the respective cis isomers. The photoregulation efficiency of RNA duplexes upon trans‐to‐cis isomerization was investigated by using melting point studies and compared with the known D ‐threoninol‐based azobenzene system, revealing a photoswitching amplitude of the new residues exceeding 90 % even at room temperature. Structural changes in the duplexes upon photoisomerization were investigated by using MM/MD calculations. The excellent photoswitching performance at room temperature and the high thermal stability make these new azobenzene residues promising candidates for in‐vivo and nanoarchitecture photoregulation applications of RNA. 相似文献
196.
Antibacterial properties have wide application in water disinfection, textile industry, medicine, and food packaging. The present work focuses on the efficacy of Cu2ZnSnS4 (CZTS) nanoparticles as a possible promising antibacterial agent along those directions. CZTS nanomaterials were synthesized following the solvo-thermal method using Teflon-lined stainless-steel autoclave. Nanoparticles were characterized using XRD, Raman spectroscopy, UV–visible spectroscopy, and SEM techniques. SEM shows that the size of synthesized nanoparticle was 50-100 ?nm. Antibacterial activity of CZTS nanoparticles was performed against ten pathogenic bacterial strains, which include 5 Gram-positive strains (viz. Staphylococcus epidermidis, Bacillus megaterium, Mycobacterium smegmatis, Lactobacillus and Staphylococcus aureus) and 5 Gram-negative strains (viz. Serratia marcescense, Salmonella typhi, Escherichia coli, Proteus vulgaris and Pseudomonas aeruginosa), using the well diffusion method. CZTS nanoparticles shows significant antibacterial activity against both the Gram-positive and Gram-negative bacterial strains. Notable increase in the antibacterial activity of CZTS nanoparticles has been observed with the increase in the concentration of nanoparticles in terms of zone of inhibition (ZOI), which helps us to study the cell toxicity. Minimum inhibitory concentration (MIC) has been observed with the lowest concentration of nanoparticles that show visible growth of bacteria, which certainly may contribute significantly toward possible medicinal applications of CZTS nanoparticles. 相似文献
197.
This paper demonstrates the use of copper electrode for the treatment of sugar processing industry wastewater (SPIW) in terms of chemical oxygen demand (COD) by applying electrocoagulation (EC) method. EC process was carried out in batch mode with electrode effective area of 0.0112 m2, supplied current intensity (CI) of 44.64 A/m2 - 223.21 A/m2, electrode gap (EG) of 0.5–2.5 cm, electrolyte (NaCl) dose (ED) of 0.5–2.5 g/L to treat SPIW with initial chemical oxygen demand (COD) of 6000 mg/L. The maximum COD removal 73% of SPIW is achieved at optimized condition of SPIW pH: 7, CI: 89.28 A/m2, EG: 1.5 cm & ED: 1.5 g/L. Sludge and scum generated during EC process were characterized by FTIR, TGA/DTA/DTG, proximate & ultimate analysis to find its applicability and their disposal. Additionally, economic study of EC treatment process at optimum condition suggest treatment cost was 11.2 US$/m3 and it indicate economic results as comparison to other available treatment processes. 相似文献
198.
We consider a system of Brownian particles confined in a two-dimensional bilobal enclosure. Varying cross-section of the confinement results in an effective entropic potential in reduced dimension. We show that the system may undergo an entropic noise-induced transition when the shape of the stationary probability density changes qualitatively from bimodal to trimodal type under the influence of a multiplicative noise. 相似文献
199.
Parnajyoti Karmakar Subhasis Mallick Biplab K. Bera Arup Mandal Subala Mondal Sudip K. Mukhopadhyay Alak K. Ghosh 《Transition Metal Chemistry》2010,35(8):911-916
The kinetics of the interaction of glycine-l-leucine (Glyleu) with cis-[Pt(cis-dach)(OH2)2]2+ (dach = 1,2-diaminocyclohexane) has been studied spectrophotometrically as a function of [cis-[Pt(cis-dach)(OH2)2]2+], [Glyleu] and temperature at pH 4.0, where the complex exists predominantly as the diaqua species and Glyleu as a zwitterion.
The substitution reaction shows two consecutive steps: the first is the ligand-assisted anation and the second is the chelation
step. The activation parameters for both the steps were evaluated using Eyring’s equation. The low ∆H1≠ (51.9 ± 2.8 kJmol−1) and large negative value of ∆S1≠ (−152 ± 8 JK−1mol−1) as well as ∆H2≠ (54.4 ± 1.7 kJmol−1) and ∆S2≠ (−162 ± 5 JK−1mol−1) indicate an associative mode of activation for both the aqua ligand substitution processes. 相似文献
200.
Tandra?Das Biplab?K.?Bera Subhasis?Mallick Parnajyoti?Karmakar Arup?Mandal Subala?Mondal Gauri?S.?De Alak?K.?Ghosh 《Transition Metal Chemistry》2010,35(7):885-890
The interaction of thiosemicarbazide with the title complex has been studied spectrophotometrically in aqueous medium as a
function of [complex], [thiosemicarbazide], pH and temperature at constant ionic strength. At pH 7.4, the reaction shows two
distinct paths; both of which are [thiosemicarbazide] dependent. A parallel reaction scheme fits well with the experimental
findings. An associative interchange mechanism is proposed for both the paths; the activation parameters calculated from Eyring
plots are ΔH1≠ = 14.2 ± 0.8 kJ mol−1, ΔS1≠ = −241 ± 2 JK−1 mol−1, ΔH2≠ = 30.8 ± 1.4 kJ mol−1 and ΔS2≠ = −236 ± 4 JK−1 mol−1. From the temperature dependence of the outer sphere association complex equilibrium constants, the thermodynamic parameters
calculated are ΔH1° = 34.25 ± 1.9 kJ mol−1, ΔS1° = 146 ± 6 J K−1 mol−1 and ΔH2° = 9.4 ± 1.1 kJ mol−1, ΔS2° = 71 ± 3 JK−1 mol−1, which gives a negative ΔG° at all temperatures studied, supporting the spontaneous formation of an outer sphere association
complex. 相似文献