| 1. |
- Brennan, Jennifer L., et al.
(författare)
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Enzymatic Activity of Lipase-Nanoparticle Conjugates and the Digestion of Lipid Liquid Crystalline Assemblies
- 2010
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 26:16, s. 13590-13599
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Tidskriftsartikel (refereegranskat)abstract
- Variants of lipase were attached to gold nanoparticles (NPs) and their enzymatic activity was studied. The two bioengineered lipase variants have been prepared with biotin groups attached to different residues on the protein outer surface. The biotinylation was evidenced by denaturing polyacrylamide gel electrophoresis and quantified by the ([2-(4'-hydroxyazobenzene)]benzoic acid spectrophotometric test. NPs of 14 +/- 1 nm diameter coated with thiolated-polyethylene glycol ligands containing controlled proportions of biotin moieties have been prepared and characterized by transmission electron microscopy, UV-vis spectroscopy, small angle neutron scattering, and elemental analysis. These biotin-functionalized NPs were conjugated to lipase using streptavidin as a linker molecule. Enzyme activity assays on the lipase-nanoparticle conjugates show that the lipase loading and activity of the NPs can be controlled by varying the percentage of biotin groups in the particle protecting coat. The lipase-NP conjugates prepared using one variant display higher activity than those prepared using the other variant, demonstrating orientation-dependent enzyme activity. Cryogenic transmission electron microscopy was used to visualize the enzymatic activity of lipase-NP on well-defined lipid substrates. It was found that lipase-coated NPs are able to digest the substrates in a different manner in comparison to the free lipase.
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| 2. |
- Hussain, Irshad, et al.
(författare)
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Controlled Step Growth of Molecularly Linked Gold Nanoparticles: From Metallic Monomers to Dimers to Polymeric Nanoparticle Chains.
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:4, s. 1934-1939
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Tidskriftsartikel (refereegranskat)abstract
- The solution-phase assembly of 15 nm gold particles into relatively linear chains of fairly controllable length of up to 1 mum is achieved by molecularly linking nanoparticles with alkanedithiols. This step-growth process can be controlled to prepare dimers, oligomers, and polymer-like gold nanoparticle chains by varying the ratio of alkanedithiols to nanoparticles. These size-controlled, relatively linear aggregates remain suspended in ethanol solution without precipitation for several weeks to months depending on the chain length. The resulting soluble nanoparticle assemblies were characterized by a variety of techniques including cryogenic transmission electron microscopy. The surface plasmon coupling of regularly spaced gold nanoparticles in these chains could be of interest in the fabrication of optical waveguide and nanoelectronic systems.
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| 3. |
- Hussain, Irshad, et al.
(författare)
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Emulsions-directed assembly of gold nanoparticles to molecularly-linked and size-controlled spherical aggregates
- 2010
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 350:1, s. 368-372
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Tidskriftsartikel (refereegranskat)abstract
- Aggregation of gold nanoparticles into soluble spherical assemblies using bi-functional ligands i.e., dithiols has recently been demonstrated but with limited control over the size of such assemblies. Herein, we report a new approach to further control the size of water dispersible spherical assemblies by confining gold nanoparticles in tiny oil droplets in water (oil-in-water emulsions) followed by their cross-linking with alkanedithiols. By controlling the size of the oil droplets and the concentration of nanoparticles, the size of spherical aggregates can be controlled from 20 to 400 nm. Cryo-TEM micrographs confirm the formation of covalently-linked soluble spherical nanoparticle assemblies within the oil emulsions in water. Such size-controlled nanoparticle assemblies may have several potential applications including those in gas sensors, controlled delivery, and optical coatings. (C) 2010 Elsevier Inc. All rights reserved.
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| 4. |
- Kabir, Mohammad, 1974, et al.
(författare)
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Giant field effect in self-assembled metallo-organic nanoscale networks
- 2005
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Ingår i: Physical Review B. ; 72, s. 235424-
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Tidskriftsartikel (refereegranskat)abstract
- Three-terminal devices have been produced by self-assembly of chemically stabilized gold clusters of 57 nm in diameter in a nanogap between the source and drain electrodes on top of an electrostatic gate made of oxidized aluminium. The conductivity of the devices with the agglomerates of clusters, self-assembled in the gap, was modulated substantially by the electric field of the gate. The effect is attributed to the mechanical deformation of the organic tunneling barriers between the gold clusters under the influence of Coulomb forces. A peculiar interplay between the mechanical deformations caused by the gate and the source-drain voltages leads to unusual current-voltage characteristics of the devices. A phenomenological theory based on these ideas has been developed.
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