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- Lovric, Jelena, 1980, et al.
(författare)
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Analysis of liposome model systems by time-of-flight secondary ion mass spectrometry
- 2014
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Ingår i: Surface and Interface Analysis: 19th International Conference on Secondary Ion Mass Spectrometry (SIMS). - : Wiley. - 0142-2421 .- 1096-9918.
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Konferensbidrag (refereegranskat)abstract
- Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is an important technique for studying chemical composition of micrometer scale objects because of its high spatial resolution imaging capabilities and chemical specificity. In this work, we focus on the application of ToF-SIMS to gain insight into the chemistry of micrometer size liposomes as a potential model for neurotransmitter vesicles. Two models of giant liposomes were analyzed: histamine and aqueous two-phase system-containing liposomes. Characterization of the internal structure of single fixed liposomes was carried out both with the Bi-3(+) and C-60(+) ion sources. The depth profiling capability of ToF-SIMS was used to investigate the liposome interior.
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| 2. |
- Keighron, Jacqueline, 1982, et al.
(författare)
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Coimmobilization of Acetylcholinesterase and Choline Oxidase on Gold Nanoparticles: Stoichiometry, Activity, and Reaction Efficiency
- 2014
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 30:38, s. 11348-11355
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid structures constructed from biomolecules and nanomaterials have been used in catalysis and bioanalytical applications. In the design of many chemically selective biosensors, enzymes conjugated to nanoparticles or carbon nanotubes have been used in functionalization of the sensor surface for enhancement of the biosensor functionality and sensitivity. The conditions for the enzyme:nanomaterial conjugation should be optimized to retain maximal enzyme activity, and biosensor effectiveness. This is important as the tertiary structure of the enzyme is often altered when immobilized and can significantly alter the enzyme catalytic activity. Here we show that characterization of a two-enzyme:gold nanoparticle (AuNP) conjugate stoichiometry and activity can be used to gauge the effectiveness of acetylcholine detection by acetylcholine esterase (AChE) and choline oxidase (ChO). This was done by using an analytical approach to quantify the number of enzymes bound per AuNP and monitor the retained enzyme activity after the enzyme:AuNP synthesis. We found that the amount of immobilized enzymes differs from what would be expected from bulk solution chemistry. This analysis was further used to determine the optimal ratio of AChE:ChO added at synthesis to achieve optimum sequential enzyme activity for the enzyme:AuNP conjugates, and reaction efficiencies of greater than 70%. We here show that the knowledge of the conjugate stoichiometry and retained enzyme activity can lead to more efficient detection of acetylcholine by controlling the AChE:ChO ratio bound to the gold nanoparticle material. This approach of optimizing enzyme gold nanoparticle conjugates should be of great importance in the architecture of enzyme nanoparticle based biosensors to retain optimal sensor sensitivity.
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