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排序方式: 共有532条查询结果,搜索用时 31 毫秒
51.
Dandapat Anirban Pramanik Sourav Bysakh Sandip De Goutam 《Journal of nanoparticle research》2013,15(7):1-10
A new water-dispersible nanostructure based on magnetite (Fe3O4) and usnic acid (UA) was prepared in a well-shaped spherical form by a precipitation method. Nanoparticles were well individualized and homogeneous in size. The presence of Fe3O4@UA was confirmed by transmission electron microscopy, Fourier transform-infrared spectroscopy, and X-ray diffraction. The UA was entrapped in the magnetic nanoparticles during preparation and the amount of entrapped UA was estimated by thermogravimetric analysis. Fabricated nanostructures were tested on planktonic cells growth (minimal inhibitory concentration assay) and biofilm development on Gram-positive Staphylococcus aureus (S. aureus), Enterococcus faecalis (E. faecalis) and Gram-negative Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) reference strains. Concerning the influence of Fe3O4@UA on the planktonic bacterial cells, the functionalized magnetic nanoparticles exhibited a significantly improved antimicrobial activity against E. faecalis and E. coli, as compared with the Fe3O4 control. The UA incorporated into the magnetic nanoparticles exhibited a very significant inhibitory effect on the biofilm formed by the S. aureus and E. faecalis, on a wide range of concentrations, while in case of the Gram-negative microbial strains, the UA-loaded nanoparticles inhibited the E. coli biofilm development, only at high concentrations, while for P. aeruginosa biofilms, no inhibitory effect was observed. The obtained results demonstrate that the new water-dispersible Fe3O4@UA nanosystem, combining the advantages of the intrinsic antimicrobial features of the UA with the higher surface to volume ratio provided by the magnetic nanocarrier dispersible in water, exhibits efficient antimicrobial activity against planktonic and adherent cells, especially on Gram-positive strains. 相似文献
52.
Nisha Kushwah Soumyaditya Mula Amey P. Wadawale Meenakshi Joshi Kedarnath Gotluru Mukesh Kumar Tapan K. Ghanty Sandip K. Nayak Vimal K. Jain 《Journal of heterocyclic chemistry》2019,56(9):2499-2507
Salicylaldimine Schiff bases represent an important class of hetero‐polydentate ligands capable of forming mononuclear, binuclear, and polynuclear complexes with transition and non‐transition metals. In this report, we developed an easy synthesis of BODIPY‐based salicylaldimine Schiff bases and synthesized five new derivatives. These were characterized by elemental analysis, infrared, UV‐Vis, nuclear magnetic resonance spectroscopy, and X‐ray crystallography. Finally, one of the Schiff bases was reacted with BF3·OEt2 to synthesize corresponding bis‐BF2 boron complex. The photophysical and electrochemical properties of the Schiff bases and the boron complex were evaluated and rationalized by theoretical calculations. The bis‐BF2 boron complex showed excited state charge redistribution, thus could be useful as sensitizers for designing new dye‐sensitized solar cells. 相似文献
53.
Amol Maruti Jadhav Sandip Gangadhar Balwe Jong Su Kim Kwon Taek Lim Yeon Tae Jeong 《Tetrahedron letters》2019,60(7):560-565
An efficient, inexpensive and environmentally friendly synthesis of novel 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-b]phthalazine-5,10-dione and 3-amino-2-benzoyl-1-aryl-1H-pyrazolo[1,2-a]pyridazine-5,8-dione derivatives has been developed via one-pot three-component reaction of phthalhydrazide or maleic hydrazide, aldehydes and arylacetonitrile in the presence of catalytic amount of InCl3 as a Lewis acid catalyst under solvent-free conditions. The most important features of the present protocol are mild reaction conditions, short reaction times, high yields, and a wide range of functional group tolerance. 相似文献
54.
A convenient and highly efficient method for the synthesis of novel polyheterocyclic chromeno pyrimido[1,2-b]indazolone derivatives via a three-component condensation of 1H-indazol-3-amine, aldehydes and 4-hydroxycoumarin catalyzed by Bronsted acid ionic liquid [Et3NH][HSO4] under solvent-free reaction conditions is presented. This ionic liquid is air and water stable and easy to prepare from amine and acid. The main advantages of this protocol includes short reaction time, excellent yield, easy work-up, operational simplicity, a wide range of functional group tolerance and column chromatography-free method. The catalyst can be recovered and reused for at least four runs without any significant impact on the product yields. 相似文献
55.
Dr. N. Kodiah Beyeh Dr. Fangfang Pan Dr. Sandip Bhowmik Toni Mäkelä Prof. Robin H. A. Ras Acad. Prof. Kari Rissanen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1355-1361
N‐Alkyl ammonium resorcinarene salts (NARYs, Y=triflate, picrate, nitrate, trifluoroacetates and NARBr) as tetravalent receptors, are shown to have a strong affinity for chlorides. The high affinity for chlorides was confirmed from a multitude of exchange experiments in solution (NMR and UV/Vis), gas phase (mass spectrometry), and solid‐state (X‐ray crystallography). A new tetra‐iodide resorcinarene salt (NARI) was isolated and fully characterized from exchange experiments in the solid‐state. Competition experiments with a known monovalent bis‐urea receptor ( 5 ) with strong affinity for chloride, reveals these receptors to have a much higher affinity for the first two chlorides, a similar affinity as 5 for the third chloride, and lower affinity for the fourth chloride. The receptors affinity toward chloride follows the trend K1?K2?K3≈ 5 >K4, with Ka=5011 m ?1 for 5 in 9:1 CDCl3/[D6]DMSO. 相似文献
56.
Tania Chowdhury Kaushik Bera Debabrata Samanta Sandip Dolui Suvendu Maity Nakul C. Maiti Prasanta Kumar Ghosh Debasis Das 《应用有机金属化学》2020,34(4):e5556
Four new zinc (II) complexes [Zn (HL1H)Br2] (1), [Zn (HL1H)Cl2] (2), [Zn2(HL2)Br3] (3), and [Zn (HL2)Cl] (4) have been synthesized by adopting template synthetic strategy and utilizing two homologous Schiff base ligands (H2L1 = 4-bromo-2-{[2-(2-hydroxyethylamino)-ethylimino]-methyl}-6-methoxyphenol, H2L2 = 4-bromo-2-{[3-(2-hydroxyethylamino)propylimino]methyl}-6-methoxyphenol), differing in one -CH2- unit in the ligating backbone, by adopting template synthetic strategy. All the complexes have been characterized by single crystal X-ray diffraction analysis as well as by other routine physicochemical techniques. Ligand mediated structural variations have been observed and rationalized by density functional theoretical (DFT) calculations. Interaction of the complexes 1–4 with Bovine Serum Albumin protein (BSA) has been studied by different spectroscopic techniques. A complete thermodynamic profile (ΔHo, ΔSo and ΔGo) was evaluated initially from the change in absorption and fluorescence spectra upon addition of BSA to the complexes. Appreciable binding constant values in the range ~ 0.94–4.51 × 104 M−1 indicate efficient binding tendency of the complexes to BSA with the sequence 1 ≅ 2 > 3 ≅ 4. Circular dichroism (CD), isothermal calorimetric titration experiments, molecular docking and molecular dynamics have been performed to gain deep insight into the binding regions of complex 1 to BSA. Experimental evidences suggest an interaction of zinc complexes at the surface of BSA protein and this particular binding has been exploited to determine unknown concentration of BSA protein. For this purpose complex 1 was explored as a BSA protein quantification tool. 相似文献
57.
A chiral Schiff-base compound, 4-methyl-2,6-bis-[(2-hydroxy-1-phenylethylimino)methyl]phenol, is found to act as highly enantioselective fluorescent agent for α-hydroxycarboxylic acid, e.g., mandelic acid. It is observed that, within a certain concentration range, one enantiomer of the chiral acid can increase the fluorescence intensity of the Schiff-base compound 122-fold while the other enantiomer enhances the intensity only 42-fold. Such highly enantioselective responses towards the chiral acid make the unusual Schiff-base compound attractive as a fluorescent sensor for determining the enantiomeric composition of α-hydroxycarboxylic acids. 相似文献
58.
J.S. Yadav B.V. Subba Reddy Swapan Kumar Biswas Sandip Sengupta P. Vishnumurthy 《Tetrahedron letters》2008,49(6):1034-1036
Phenacyl bromides undergo smooth vic-diallylation and dipropargylation with allyl and propargyl indium reagents generated in situ from metallic indium and allyl or propargyl bromide to produce 4-arylocta-1,7-dien-4-ol derivatives in good yields. Phenacyl chloride and azide also participated effectively in bis-allylation. Similar results are also obtained from in situ generated allyl or propargyl zinc bromide. 相似文献
59.
The synthesis of lairdinol A, a component of the host-selective phytotoxin depsilairdin, was achieved in 12 steps (18% overall yield) without the use of protecting groups starting with the Diels-Alder reaction of (R)-carvone with 3-trimethylsilyloxy-1,3-pentadiene. The key step established the trans ring fusion by preferential epoxidation of a trans-fused enone in an equilibrating mixture of the cis-fused and trans-fused diastereomers (i.e., equivalent to a dynamic kinetic resolution of these isomers). The synthesis confirms the absolute configurations of lairdinol A and its enantiomer, cyperusol C. 相似文献
60.
N.L. Misra Sangita Dhara V.C. Adya S.V. Godbole K.D. Singh Mudher S.K. Aggarwal 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Applicability of Total Reflection X-ray Fluorescence (TXRF) spectrometry for the determination of trace metals at concentration of µg/g level in thorium oxide was studied. The TXRF spectrometer was calibrated using a multielement standard solution and the method was validated by analyzing another multielement standard solution. Sample preparation conditions were optimized for the TXRF determinations of trace metals in thorium oxide. The elements K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Ba and Pb present in thorium oxide standards were determined after dissolving them in HNO3/HF mixture and separating the bulk matrix, thorium, by solvent extraction using tri-n-butyl phosphate (TBP) and tri-n-octyl phosphine oxide (TOPO) as extractants. A comparison of TXRF determined concentrations of trace elements Ca, V, Cr, Mn, Fe, Ni and Cu with the certified values shows that TXRF determined concentrations have an RSD of 20% (1 s for n = 4) and are within an agreement of 20% of the certified values in most of the cases. 相似文献