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61.
Stefan M Marius S Hritcu L Lucian H Mihasan M Marius M Pricop D Daniela P Gostin I Irina G Olariu RI Romeo-Iulian O Dunca S Simona D Melnig V Viorel M 《Journal of materials science. Materials in medicine》2011,22(4):789-796
In the present study, we report enhanced antimicrobial properties of 29 and 23 nm silver nanoparticles (Ag NPs) obtained by
electrochemical synthesis in poly(amide-hydroxyurethane) media. Antibacterial activity assessed by disk diffusion method indicates
that silver nanoparticles produced inhibition zones for both Escherichia coli and Staphylococcus aureus depending on silver concentration. The bacterial growth curve performed in the presence of silver nanoparticles showed a
stronger antibacterial effect at lower concentrations than those described in the earlier reports. The effect was both dose
and size dependent and was more pronounced against Gram negative bacteria than Gram positive one. The smallest Ag NPs used
had a bactericidal effect resulting in killing E. coli cells. Scanning electron microscopy analysis indicated major damage and morphology changes of the silver nanoparticles treated
bacterial cells. The major mechanism responsible for the antibacterial effect probably consists in clusters formation and
nanoparticles anchorage to the bacterial cell surface. 相似文献
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A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands 下载免费PDF全文
Tjaard de Roo Johannes Haase Janine Keller Christopher Hinz Marius Schmid Denis V. Seletskiy Helmut Cölfen Alfred Leitenstorfer Stefan Mecking 《Advanced functional materials》2014,24(18):2714-2719
Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (Mn = 4 × 103 g mol?1, Mw/Mn < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot. 相似文献
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Laminar steady compressible flow between close rotating thermally conducting axisymmetric disks with inflow was investigated by means of a numerical solution of the Navier-Stokes equation and an asymptotic analysis. The approximate solution, obtained for small ?, E and H (Rossby and Ekman numbers, and height/radius, respectively) is valid for “merged”, “close” and “separate” boundary layers on the disks, corresponding to β? 1, and β? 1, respectively (where , and ρ is the non-dimensional density). These three cases may appear simultaneously in different regions of the same system due to the large variation of ρ in the radial direction. The small ? (i.e. negligible convection terms) does not necessarily imply small perturbations of the pressure, and a special treatment of the pressure term was used in order to account for this feature, which sometimes culminates in inversion of the radial pressure gradient. Thenumerical solution was obtained by a finite-difference, modified Cheng-Allen method, using a non-uniform mesh. The numerical and the approximate solution are in good agreement. 相似文献
67.
Nilges Michael; Gronenborn Angela M.; Brunger Axel T.; Clore G. Marius 《Protein engineering, design & selection : PEDS》1988,2(1):27-38
An automated method, based on the principle of simulated annealing,is presented for determining the three-dimensional structuresof proteins on the basis of short (<5 Å) interprotondistance data derived from nuclear Overhauser enhancement (NOE)measurements. The method makes use of Newton's equations ofmotion to increase temporarily the temperature of the systemin order to search for the global minimum region of a targetfunction comprising purely geometric restraints. These consistof interproton distances supplemented by bond lengths, bondangles, planes and soft van der Waals repulsion terms. The latterreplace the dihedral, van der Waals, electrostatic and hydrogen-bondingpotentials of the empirical energy function used in moleculardynamics simulations. The method presented involves the implementationof a number of innovations over our previous restrained moleculardynamics approach [Clore,G.M., Brünger,A.T., Karplus,M.and Gronenborn,A.M. (1986) J. Mol. Biol., 191, 523551].These include the development of a new effective potential forthe interproton distance restraints whose functional form isdependent on the magnitude of the difference between calculatedand target values, and the design and implementation of robustand fully automatic protocol. The method is tested on threesystems: the model system crambin (46 residues) using X-raystructure derived interproton distance restraints, and potatocarboxypeptidase inhibitor (CPI; 39 residues) and barley serineproteinase inhibitor 2 (BSPI-2; 64 residues) using experimentallyderived interproton distance restraints. Calculations were carriedout starting from the extended strands which had atomic r.m.s.differences of 57, 38 and 33 Å with respect to the crystalstructures of BSPI-2, crambin and CPI respectively. Unbiasedsampling of the conformational space consistent with the restraintswas achieved by varying the random number seed used to assignthe initial velocities. This ensures that the different trajectoriesdiverge during the early stages of the simulations and onlyconverge later as more and more interproton distance restraintsare satisfied. The average backbone atomic r.m.s. differencebetween the converged structures is 2.2 ± 0.3 Åfor crambin (nine structures), 2.4 ± 0.3 Å forCPI (eight structures) and 2.5 ± 0.2 Å for BSPI-2(five structures). The backbone atomic r.m.s. difference betweenthe mean structures derived by averaging the coordinates ofthe converged structures and the corresponding X-ray structuresis 1.2 Å for crambin, 1.6 Å for CPI and 1.7 Åfor BSPI-2. 相似文献
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Identification and composition of turnip root lipids 总被引:22,自引:0,他引:22
Two varieties of turnip, Laurentian and Wye, were examined for their lipid and fatty acid composition. Lipids extracted with
80% ethanol contained variable quantities of phosphatidic acid, which was considered to be an artifact. Crude lipids were
fractionated by TLC, and fatty acids and sterols were analyzed by GLC. Among the common phospholipids, cardiolipid and phosphatidyl
glycerol were abundant components. Linolenic acid comprised 60% of the total fatty acids. β-Sitosterol was the principal sterol,
and about half of the carotenoids was lycopene. No great differences between the two varieties studied were observed however.
Contribution No. 53 of the Food Research Institute, Canada Department of Agriculture, Ottawa. 相似文献
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