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排序方式: 共有314条查询结果,搜索用时 15 毫秒
91.
Klein MP Jacobs BW Ong MD Fares SJ Robinson DB Stavila V Wagner GJ Arslan I 《Journal of the American Chemical Society》2011,133(24):9144-9147
A well characterized and predictable aging pattern is necessary for practical energy storage applications of nanoporous particles that facilitate rapid transport of ions or redox species. Here we use STEM tomography with segmentation to show that surface diffusion and grain boundary diffusion are responsible for pore evolution at intermediate and higher temperatures, respectively. This unprecedented three dimensional understanding of pore behavior as a function of temperature suggests routes for optimizing pore stability in future energy storage materials. 相似文献
92.
A series of novel stimuli-responsive AB, ABA, and BAB type block copolymers based on 6-O-methacryloyl-1,2:3,4-di-O-isopropylidene-d-galactopyranose (MAIpGP:A block) and 2-(N,N-dimethylamino)ethyl methacrylate (DMAEMA: B block) were synthesized via ATRP techniques using ethyl 2-bromoisobutyrate (EBiB) as monofunctional ATRP initiator in the case of diblock copolymer and diethyl meso-2,5-dibromoadipate (DEDBA) as bifunctional ATRP initiator in the case of triblock copolymers. The PMAIpGP blocks of the AB, ABA, and BAB type linear block copolymers were converted to water soluble PMAGP blocks via deprotection process under mild acidic conditions. Both proton NMR and DLS studies demonstrated that block copolymers were temperature-sensitive, whereby the lower critical solution temperature (LCST) of polymers varied with the polymerization degrees of comonomers in the block copolymers. LCST was determined to be between ∼35 °C and 55 °C depending on the type and the comonomer compositions of the block copolymers. It was observed that an increase on the percentage of hydrophilic PMAGP block in block copolymer caused an increase on the LCST value as expected. 相似文献
93.
Marya Aziz Saeed Ahmad Umair Khurshid Irfan Pervaiz Arslan Hussain Lodhi Nasrullah Jan Sameera Khurshid Muhammad Adeel Arshad Mohamed M. Ibrahim Gaber A. M. Mersal Fahaad S. Alenazi Ahmed Awadh Saleh Alamri Juwairiya Butt Hammad Saleem Zeinhom M. El-Bahy 《Molecules (Basel, Switzerland)》2022,27(20)
Plants of the genus Strobilanthes have notable use in folklore medicines as well as being used for pharmacological purposes. The present work explored the biological predispositions of Strobilanthes glutinosus and attempted to accomplish a comprehensive chemical profile through GC-MS of different fractions concerning polarity (chloroform and n-butanol) and LC-ESI-MS of methanolic extract by both positive and negative ionization modes. The biological characteristics such as antioxidant potential were assessed by applying six different methods. The potential for clinically relevant enzyme (α-amylase, α-glucosidase, and tyrosinase) inhibition was examined. The DPPH, ABTS, CUPRAC, and FRAP results revealed that the methanol fraction presented efficient results. The phosphomolybdenum assay revealed that the n-hexane fraction showed the most efficient results, while maximum metal chelation potential was observed for the chloroform fraction. The GC-MS profiling of n-butanol and chloroform fractions revealed the existence of several (110) important compounds presenting different classes (fatty acids, phenols, alkanes, monoterpenes, diterpenes, sesquiterpenoids, and sterols), while LC-ESI-MS tentatively identified the presence of 44 clinically important secondary metabolites. The n-hexane fraction exhibited the highest potential against α-amylase (497.98 mm ACAE/g extract) and α-glucosidase (605.85 mm ACAE/g extract). Significant inhibitory activity against tyrosinase enzyme was displayed by fraction. Six of the prevailing compounds from the GC-MS study (lupeol, beta-amyrin, stigmasterol, gamma sitosterol, 9,12-octadecadienoic acid, and n-hexadecanoic acid) were modelled against α-glucosidase and α-amylase enzymes along with a comparison of binding affinity to standard acarbose, while three compounds identified through LC-ESI-MS were docked to the mushroom tyrosinase enzyme and presented with significant biding affinities. Thus, it is assumed that S. glutinosus demonstrated effective antioxidant and enzyme inhibition prospects with effective bioactive molecules, potentially opening the door to a new application in the field of medicine. 相似文献
94.
I¸ıl Hacıbekiroğlu Pelin Köseoğlu Yılmaz Nesrin Ha¸imi Ersin Kılınç Veysel Tolan 《Natural product research》2015,29(5):444-446
This study reports in vitro anticholinesterase, antioxidant and antimicrobial effects of the n-hexane, dichloromethane, ethanol and ethanol–water extracts prepared from Pistacia terebinthus L. fruits and Pistacia khinjuk Stocks seeds as well as their total phenolic and flavonoid contents, and fatty acid compositions. Ethanol and ethanol–water extracts of both species exhibited higher anticholinesterase activity than galanthamine. Among ABTS, DPPH and CUPRAC assays, the highest antioxidant capacity of the extracts was found in the last one. P. terebinthus ethanol extract being rich in flavonoid content showed the best cupric reducing effect. All extracts possessed no antimicrobial activity. The main fatty acid in P. terebinthus fruits (52.52%) and P. khinjuk seeds (59.44%) was found to be oleic acid. Our results indicate that P. terebinthus fruits and P. khinjuk seeds could be a good source of anticholinesterase compounds, and could be phytochemically investigated. 相似文献
95.
Serpil Demir?smail Özdemir Bekir ÇetinkayaHakan Arslan Don VanDerveer 《Polyhedron》2011,30(1):195-200
The new well-defined and air-stable ortho-xylyl-linked N-heterocyclic carbene (NHC) Pd complexes (2a-d) have been synthesized and characterized by elemental analysis, 1H NMR, 13C NMR, IR spectroscopy, and single crystal X-ray diffraction studies. The palladium atom in the complex 2a lies on a crystallographic mirror plane and can be described as having a square-planar coordination environment with the carbene atoms of the benzimidazole rings of the ligand occupying two coordination sites in cis positions. Two further coordination sites are occupied by chloride ligands. The benzimidazole rings are connected to each other by an ortho-xylyl bridge. The catalytic activity of these palladium complexes has been tested in the coupling reactions of various N-containing substrates with bromobenzene. A preliminary catalytic study shows that the bis(NHC)-Pd complexes are highly active in the Buchwald-Hartwig amination reaction. 相似文献
96.
Musharraf SG Ali A Ali RA Yousuf S Rahman AU Choudhary MI 《Rapid communications in mass spectrometry : RCM》2011,25(1):104-114
Structural elucidation and gas‐phase fragmentation of ten withanolides (steroidal lactones) were studied using a positive ion electrospray ionization quadropole time‐of‐flight mass spectrometry (ESI‐QqTOF‐MS/MS) hybrid instrument. Withanolides form an important class of plant secondary metabolites, known to possess a variety of biological activities. Withanolides which possess hydroxyl groups at C‐4, C‐5, C‐17, C‐20, and C‐27, and an epoxy group at C‐5/C‐6, were evaluated to determine the characteristic fragments and their possible pathways. ESI‐QqTOF‐MS (positive ion mode) showed the presence of the protonated molecules [M + H]+. Low‐energy collision‐induced dissociation tandem mass spectrometric (CID‐MS/MS) analysis of the protonated molecule [M + H]+ indicated multiple losses of water and the removal of the C‐17‐substituted lactone moiety affording the [M + H–Lac]+ product ion as the predominant pathways. However, withanolides containing a hydroxyl group at C‐24 of the lactone moiety showed a different fragmentation pathway, which include the loss of steroidal part as a neutral molecule, with highly diagnostic ions at m/z 95 and 67 being generated from the cleavage of lactone moiety. Our results also determined the influence of the presence and positions of hydroxyl and epoxy groups on product ion formation and stability. Moreover, the knowledge of the fragmentation pattern was utilized in rapid identification of withanolides by the LC/MS/MS analysis of a Withania somnifera extract. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
97.
98.
Aytek Yılmaz Bilge Taner Pervin Deveci Aslıhan Yılmaz Obalı Uğur Arslan Ertan Şahin H. İsmet Uçan Emine Özcan 《Polyhedron》2010
A new vic-dioxime ligand bearing an important pharmacophore substituent, anti-1-(4-benzylpiperazine-1-yl) phenylglyoxime (LH2) (Scheme 1), has been synthesized and its nickel(II) complex was obtained by the reaction of NiCl2·6H2O and the ligand. The characterization of the newly formed compounds was performed by elemental analysis, FT-IR, 1D NMR (1H, 13C, DEPT), 2D NMR (HMBC), ESI mass-spectrometry, TG/DTA, X-ray crystallography. The antibacterial activity was also studied against Staphylococcus aureus ATCC 25923, Streptococcus mutans RSHM 676, Enterococcus faecalis ATCC 29212, Lactobacillus acidophilus RSHM 06029, Escherichia coli ATCC 25922, E. coli ATCC 35218, Pseudomonasaeruginosa ATCC 27853. The antimicrobial test results indicated that all the compounds have mild antibacterial activity against both Gram negative and Gram positive bacterial species. 相似文献
99.
Rainer Kahner Benedikt Waerder Hasan Kemal Arslan Heinz Rehage 《Colloid and polymer science》2010,288(4):461-468
In this publication we describe a new self-association process, which leads to the formation of ultra-thin alginate layers
at the interface between oil and water. The water phase contains a highly dilute solution of sodium alginate. These macromolecules
are negatively charged and they are not surface active. The oil phase contains a small concentration of positively charged
surfactants. At the interface between oil and water, the cationic surfactants tend to form complexes with the negatively charged
alginate polyelectrolytes in the aqueous solutions. This leads to striking adsorption processes of the solved polysaccharide
molecules at the oil-water interface. Upon the addition of calcium ions, a cross-linking process sets in and one obtains the
thin viscoelastic membranes, which are anchored at the interface between oil and water. The thickness of these membranes is
of the order of 0.2 mm. Similar structures can also be formed by solving positively charged Gemini surfactants in the oil
phase. In this case, the cationic surfactant molecules induce the adsorption processes of alginate macromolecules, and they
also act as cross-linking compounds. In a series of experiments, we measured the surface rheological properties of these ultra-thin
alginate membranes. The results of these investigations point to the presence of electrostatically stabilized membranes. Special
interest was given to the influence of the guluronate content of the alginates, which is important for the cross-linking mechanism
according to the egg-box model. Finally, this article finishes with the discussion of the proposed building mechanisms of
these membranes. 相似文献
100.
Duymus H Arslan M Kucukislamoglu M Zengin M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(5):1120-1124
Charge transfer (CT) complexes of some non-steroidal anti-inflammatory drugs, naproxen and etodolac which are electron donors with some pi-acceptors, such as tetracyanoethylene (TCNE), 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), p-chloranil (p-CHL), have been investigated spectrophotometrically in chloroform at 21 degrees C. The coloured products are measured spectrophotometrically at different wavelength depending on the electronic transition between donors and acceptors. Beer's law is obeyed and colours were produced in non-aqueous media. All complexes were stable at least 2 h except for etodolac with DDQ stable for 5 min. The equilibrium constants of the CT complexes were determined by the Benesi-Hildebrand equation. The thermodynamic parameters DeltaH, DeltaS, DeltaG degrees were calculated by Van't Hoff equation. Stochiometries of the complexes formed between donors and acceptors were defined by the Job's method of the continuous variation and found in 1:1 complexation with donor and acceptor at the maximum absorption bands in all cases. 相似文献