| 1. |
- Höök, Fredrik, 1966, et al.
(author)
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Supported lipid bilayers, tethered lipid vesicles, and vesicle fusion investigated using gravimetric, plasmonic, and microscopy techniques
- 2007
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In: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2
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Journal article (peer-reviewed)abstract
- This article summarizes our most recent contributions to the rapidly growing field of supported lipid assemblies with emphasis on current studies addressing both fundamental and applied aspects of supported lipid bilayer (SLB) and tethered lipid vesicles (TLVs) to be utilized in sensing applications. The new insights obtained from combining the quartz crystal microbalance with dissipation monitoring technique with surface plasmon resonance are described, and we also present recent studies in which nanoplasmonic sensing has been used in studies of SLBs and TLVs. To gain full control over the spatial arrangement of TLVs in both two and three dimensions, we have developed a method for site-selective and sequence-specific sorting of DNA-tagged vesicles to surfaces modified with complementary DNA. The combination of this method with nanoplasmonic sensing formats is covered as well as the possibility of using DNA-modified vesicles for the detection of unlabeled DNA targets on the single-molecule level. Finally, a new method for membrane fusion induced by hybridization of vesicle-anchored DNA is demonstrated, including new results on content mixing obtained with vesicle populations encapsulating short, complementary DNA strands.
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| 2. |
- Gunnarsson, Anders, 1981, et al.
(author)
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Kinetic and thermodynamic characterization of single-mismatch discrimination using single-molecule imaging
- 2009
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In: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 37:14, s. e99 (art no)-
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Journal article (peer-reviewed)abstract
- A single-molecule detection setup based on total internal reflection fluorescence (TIRF) microscopy has been used to investigate association and dissociation kinetics of unlabeled 30mer DNA strands. Single-molecule sensitivity was accomplished by letting unlabeled DNA target strands mediate the binding of DNA-modified and fluorescently labeled liposomes to a DNA-modified surface. The liposomes, acting as signal enhancer elements, enabled the number of binding events as well as the residence time for high affinity binders (K-d
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| 3. |
- Jonsson, Magnus, 1981, et al.
(author)
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Nanoplasmonic biosensing with focus on short-range ordered nanoholes in thin metal films
- 2008
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In: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:3, s. FD30-FD40
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Journal article (peer-reviewed)abstract
- The resonance conditions for excitation of propagating surface plasmons at planar metal/dielectric interfaces and localized surface plasmons associated with metal nanostructures are both sensitive to changes in the interfacial refractive index. This has made these phenomena increasingly popular as transducer principles in label-free sensing of biomolecular recognition reactions. In this article, the authors review the recent progress in the field of nanoplasmonic bioanalytical sensing in general, but set particular focus on certain unique possibilities provided by short-range ordered nanoholes in thin metal films. Although the latter structures are formed in continuous metal films, while nanoparticles are discrete entities, these two systems display striking similarities with respect to sensing capabilities, including bulk sensitivities, and the localization of the electromagnetic fields. In contrast, periodic arrays of nanoholes formed in metal films, most known for their ability to provide wavelength-tuned enhanced transmission, show more similarities with conventional propagating surface plasmon resonance. However, common for both short-range ordered and periodic nanoholes formed in metal films is that the substrate is electrically conductive. Some of the possibilities that emerge from sensor templates that are both electrically conductive and plasmon active are discussed and illustrated using recent results on synchronized nanoplasmonic and quartz crystal microbalance with dissipation monitoring of supported lipid bilayer formation and subsequent biomolecular recognition reactions. Besides the fact that this combination of techniques provides an independent measure of biomolecular structural changes, it is also shown to contribute with a general means to quantify the response from nanoplasmonic sensors in terms of bound molecular mass. c 2008 American Vacuum Society.
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| 4. |
- Jönsson, Peter, 1981, et al.
(author)
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Mechanical Behavior of a Supported Lipid Bilayer under External Shear Forces
- 2009
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In: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 25:11, s. 6279-6286
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Journal article (peer-reviewed)abstract
- Shear forces from a pressure-driven bulk flow in a microfluidic channel can be used to induce and control the motion of a supported lipid bilayer (SLB) formed on the walls of the channel. We here present a theoretical model that relates the experimentally observed drift velocities of an egg yolk phosphatidylcholine (egg PC) SLB to the hydrodynamic drag force from the bulk flow, the intermonolayer friction coefficient, b, of the bilayer, and the friction coefficient, b(ls) between the lower leaflet of the bilayer and the supporting substrate. The drift velocity and diffusivity of the lipids in the SLB were obtained by photobleaching a delimited area of fluorescently labeled lipids and subsequently monitoring the recovery and convective motion of the bleached spot. A striking observation was that the drift velocity of the lipids was observed to be nearly 6 orders of magnitude smaller than the bulk velocity at the center of the channel. This predicts a value for b(ls) that is at least 25 times as high as predicted by the traditional model with the SLB and the support spaced by a homogeneous 1 nm thick film of water. In addition, the intermonolayer friction coefficient was estimated to 2 x 10(7) Pa s/m, a value that increased after addition of glycerol to the bulk solution. This increase was accompanied by an equal decrease in the lipid diffusivity, with both observations indicating an increased viscous drag within the bilayer when glycerol was added to the bulk solution.
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| 5. |
- Jönsson, Peter, 1981, et al.
(author)
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Shear-Driven Motion of Supported Lipid Bilayers in Microfluidic Channels
- 2009
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 131:14, s. 5294-5297
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Journal article (peer-reviewed)abstract
- In this work, we demonstrate how a lateral motion of a supported lipid bilayer (SLB) and its constituents can be created without relying on self-spreading forces. The force driving the SLB is instead a viscous shear force arising from a pressure-driven bulk flow acting on the SLB that is formed on a glass wall inside a microfluidic channel. In contrast to self-spreading bilayers, this method allows for accurate control of the bilayer motion by altering the bulk flow in the channel. Experiments showed that an egg yolk phosphatidylcholine SLB formed on a glass support moved in a rolling motion under these shear forces, with the lipids in the upper leaflet of the bilayer moving at twice the velocity of the bilayer front. The drift velocity of different lipid probes in the SLB was observed to be sensitive to the interactions between the lipid probe and the surrounding molecules, resulting in drift velocities that varied by up to I order of magnitude for the different lipid probes in our experiments. Since the method provides a so far unattainable control of the motion of all molecules in an SLB, we foresee great potential for this technique, alone or in combination with other methods, for studies of lipid bilayers and different membrane-associated molecules.
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| 6. |
- Tabaei, Seyed, 1978, et al.
(author)
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Self-assembly formation of multiple DNA-tethered lipid bilayers
- 2009
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In: Journal of Structural Biology. - : Elsevier BV. - 1047-8477 .- 1095-8657. ; 168:1, s. 200-206
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Journal article (peer-reviewed)abstract
- Inspired by natural cell-cell junctions, where membrane-residing proteins control the separation between two or more membranes without interfering with their integrity, we report a new self-assembly route for formation of multiple highly fluid tethered lipid bilayers with the inter-membrane volume geometrically confined by membrane-anchored DNA duplexes. The formation of multiple planar membrane-membrane junctions were accomplished using disk shaped bicelles, composed of a mixture of the long-chained dimyristoyl phosphatidylcholine (DMPC) and the short-chained dihexanoyl PC further stabilized with the positively charged detergent hexadecyl-trimethyl-ammonium bromide (CTAB). Quartz crystal microbalance with dissipation (QCM-D) monitoring and fluorescence microscopy and fluorescence recovery after photobleaching (FRAP) were used to monitor the formation and to characterize the integrity of the self-assembled lipid-DNA architecture. (C) 2009 Elsevier Inc. All rights reserved.
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