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151.
Banerjee A Basu K Sengupta PK 《Journal of photochemistry and photobiology. B, Biology》2007,89(2-3):88-97
We have studied the confinement of robinetin, a therapeutically active plant flavonol, in cyclodextrin (CDx) nanocavities, using steady state and time resolved fluorescence spectroscopy. Enhanced tautomer emission (arising from excited state intramolecular proton transfer (ESIPT)) as well as dramatically blue shifted (approximately 10 nm in beta-CDx and approximately 33 nm in SHP beta-CDx) normal fluorescence observed upon addition of the beta-CDxs indicate that robinetin readily enters the doughnut-shaped hydrophobic cavity of beta-CDx where the chromone moiety is well shielded from external hydrogen bonding perturbations. Detailed analyses of the fluorescence data (emission profile, anisotropy, decay times) indicate that robinetin forms 1:1 inclusion complexes with both natural and chemically modified beta-cyclodextrins (beta-CDx and SHP beta-CDx) with affinity constant values K=195+/-17 M(-1) and 1055+/-48 M(-1) respectively, indicating the prospective utility of SHP beta-CDx in particular as an effective drug carrier. Unlike beta-CDxs, alpha-CDxs do not form inclusion complexes with robinetin. To further characterize the robinetin/beta-CDxs complexes, circular dichroism (CD) spectroscopic studies have been performed, which reveal that incorporation of robinetin molecules in the chiral environment of the beta-CDxs strongly affects the electronic transitions of robinetin leading to the occurrence of positive induced circular dichroism (ICD) bands in the near ultra-violet (UV) region. Molecular mechanics calculations show that the inclusion complex with the chromone ring inserted into the beta-CDx cavity is most favorable, in agreement with our spectroscopic data. 相似文献
152.
Han X Critchley K Zhang L Pradeep SN Bushby RJ Evans SD 《Langmuir : the ACS journal of surfaces and colloids》2007,23(3):1354-1358
We introduce a new method for forming tethered bilayer lipid membranes on surfaces patterned using a photocleavable self-assembled monolayer (SAM). A SAM terminated with a hydrophobic fluorocarbon residue was bound to a gold surface through a link containing a photocleavable ortho-nitrobenzyl moiety. Hydrophilic regions were produced by irradiation with soft UV (365 nm) through a photomask. The patterned surface was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Tethered bilayer lipid membranes with well-defined bilayer and monolayer regions were then formed by exposure to egg PC vesicles. The membranes had resistance and capacitance values of 0.52 MOmega.cm2 and 0.83 microF.cm-2, respectively. 相似文献
153.
AnupaK. Patnaik N. SubbaRao Pradeep Kumar AshwaniK. Sharma BhagwanS. Garg KailashC. Gupta 《Helvetica chimica acta》2000,83(2):322-327
A simple protocol for the preparation of high‐loading supports, suitable for large‐scale synthesis of oligonucleotides, has been developed. The method involves the use of inexpensive reagents and is amenable to large‐scale preparation of supports. The derivatized supports were successfully employed in an automated DNA synthesizer without any difficulty. The quality of the synthesized oligonucleotides was found to be comparable to that of the corresponding oligomers prepared with commercially available standard supports. 相似文献
154.
Sainyam Galhotra Karthikeyan Shanmugam Prasanna Sattigeri Kush R. Varshney 《Entropy (Basel, Switzerland)》2021,23(12)
The deployment of machine learning (ML) systems in applications with societal impact has motivated the study of fairness for marginalized groups. Often, the protected attribute is absent from the training dataset for legal reasons. However, datasets still contain proxy attributes that capture protected information and can inject unfairness in the ML model. Some deployed systems allow auditors, decision makers, or affected users to report issues or seek recourse by flagging individual samples. In this work, we examine such systems and consider a feedback-based framework where the protected attribute is unavailable and the flagged samples are indirect knowledge. The reported samples are used as guidance to identify the proxy attributes that are causally dependent on the (unknown) protected attribute. We work under the causal interventional fairness paradigm. Without requiring the underlying structural causal model a priori, we propose an approach that performs conditional independence tests on observed data to identify such proxy attributes. We theoretically prove the optimality of our algorithm, bound its complexity, and complement it with an empirical evaluation demonstrating its efficacy on various real-world and synthetic datasets. 相似文献
155.
Chinmay Das Muhiddin Elguweri Peijun Jiang Shuhui Kang Mauritz Kelchtermans Tom C. B. McLeish Matthew Parkinson Daniel J. Read Michael P. Redlich Pradeep P. Shirodkar Johannes M. Soulages 《大分子反应工程》2019,13(3)
The flow response of branched entangled resins is dominated by the branching topology of the constituent molecules, a property that is not directly accessible using experimental analytical tools for industrially relevant complex resins. In this paper, the controlled terpolymerization of ethylene, 1,9‐decadiene, and either hexene or octene in a continuous stirred tank reactor with a metallocene catalyst, is reported. The synthesized samples are characterized extensively with various analytical tools and their rheological properties are measured with small amplitude oscillatory shear and start‐up uniaxial extension experiments. A model is developed for the polymerization process with the mass balance during synthesis providing strong constraints on the rate constants. In silico ensembles of molecules, generated via Monte Carlo sampling, are used to reproduce the experimental results. The computer model allows us to infer the detailed branching structure of the molecules and to predict the optimum range of reactor conditions for this synthesis. 相似文献
156.
A. P. Gnana Prakash Vinayakprasanna N. Hegde T. M. Pradeep N. Pushpa P. K. Bajpai S. P. Patel 《辐射效应与固体损伤》2017,172(11-12):922-930
The total dose effects of 5?MeV proton and Co-60 gamma irradiation in the dose range from 1 to 100?Mrad on advanced 200?GHz Silicon–Germanium heterojunction bipolar transistors (SiGe HBTs) are investigated. The SRIM simulation study was conducted to understand the energy loss of 5?MeV proton ions in SiGe HBT structure. Pre- and post-radiation DC figure of merits such as forward- and inverse-mode Gummel characteristics, excess base current, DC current gain and output characteristics were used to quantify the radiation tolerance of the devices. The results show that the proton creates a significant amount of damages in the surface and bulk of the transistor when compared with gamma irradiation. The SiGe HBTs shows robust ionizing radiation tolerance even up to a total dose of 100?Mrad for both radiations. 相似文献
157.
A wide variety of [1,2,3]triazolo[5,1-c][1,4]benzoxazines were synthesized through palladium-copper catalyzed reactions of 1-azido-2-(prop-2-ynyloxy)benzene with aryl/vinyl iodides. A plausible reaction mechanism has also been proposed. 相似文献
158.
Madathumpady Abubaker Habeeb Muhammed Pramod Kumar Verma Samir Kumar Pal Dr. R. C. Arun Kumar Soumya Paul Ramakrishnapillai Vyomakesannair Omkumar Dr. Thalappil Pradeep Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(39):10110-10120
A novel interfacial route has been developed for the synthesis of a bright‐red‐emitting new subnanocluster, Au23, by the core etching of a widely explored and more stable cluster, Au25SG18 (in which SG is glutathione thiolate). A slight modification of this procedure results in the formation of two other known subnanoclusters, Au22 and Au33. Whereas Au22 and Au23 are water soluble and brightly fluorescent with quantum yields of 2.5 and 1.3 %, respectively, Au33 is organic soluble and less fluorescent, with a quantum yield of 0.1 %. Au23 exhibits quenching of fluorescence selectively in the presence of Cu2+ ions and it can therefore be used as a metal‐ion sensor. Aqueous‐ to organic‐phase transfer of Au23 has been carried out with fluorescence enhancement. Solvent dependency on the fluorescence of Au23 before and after phase transfer has been studied extensively and the quantum yield of the cluster varies with the solvent used. The temperature response of Au23 emission has been demonstrated. The inherent fluorescence of Au23 was used for imaging human hepatoma cells by employing the avidin–biotin interaction. 相似文献
159.
Aqueous to organic phase transfer of water soluble sub-nanocluster, Au25SG18 (-SG, glutathione thiolate) is demonstrated using the phase transfer reagent, tetraoctylammonium bromide. The phase transfer
occurred by the electrostatic attraction between the hydrophilic carboxylate anion of the glutathione ligand on the cluster
surface in the aqueous phase and the hydrophobic tetraoctylammonium cation in the toluene phase. Detailed spectroscopic characterization
of the phase transferred cluster using optical absorption, photoluminescence and X-ray photoelectron spectroscopy showed that
the cluster retains its integrity during the phase transfer. The interaction of the cluster with the phase transfer reagent
can be studied with infrared spectroscopy. The phase transferred cluster can be dried and redissolved in an organic medium,
just as the original cluster. This is the first report of the phase transfer of a sub-nanocluster, keeping the cluster core
intact. The effect of dilution and pH on phase transfer of this cluster is studied in detail. This method promises several
possibilities to explore the properties, reactivity and applications of sub-nanoclusters both in the aqueous and organic phases.
Dedicated to Prof. C.N.R. Rao on his 75th birthday, whose work on phase transfer of nanoparticles has inspired this work. 相似文献
160.
The PdFe nanorods (PdFe-NRs) with tunable length were synthesized by an organic phase reaction of [Pd(acac)2] and thermal decomposition of [Fe(CO)5] in a mixture of oleyamine and octadecene at 160 °C. They show a better proton exchange membrane fuel cell (PEMFC) performance than commercial Pt/C in working voltage region of 0.80–0.65 V, due to their high intrinsic activity to oxygen reduction reaction (ORR), reduced cell inner resistance, and improved mass transport. 相似文献