| 1. |
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| 2. |
- Gunnarsson, Anders, 1981, et al.
(författare)
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Time-resolved surface-enhanced ellipsometric contrast imaging for label-free analysis of biomolecular recognition reactions on glycolipid domains
- 2012
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 84:15, s. 6538-6545
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Tidskriftsartikel (refereegranskat)abstract
- We have applied surface-enhanced ellipsometry contrast (SEEC) imaging for time-resolved label-free visualization of biomolecular recognition events on spatially heterogeneous supported lipid bilayers (SLB). Using a conventional inverted microscope equipped with total internal reflection (TIR) illumination, biomolecular binding events were monitored with a lateral resolution near the optical diffraction limit at an acquisition rate of ∼1 Hz with a sensitivity in terms of surface coverage of ∼1 ng/cm2. Despite the significant improvement in spatial resolution compared to alternative label-free surface-based imaging technologies, the sensitivity remains competitive with surface plasmon resonance (SPR) imaging and imaging ellipsometry. The potential of the technique to discriminate local differences in protein binding kinetics was demonstrated by time-resolved imaging of anti-GalCer antibodies binding to phase-separated lipid bilayers consisting of phosphatidylcholine (POPC) and galactosylceramide (GalCer). A higher antibody binding capacity was observed on the GalCer-diluted fluid region in comparison to the GalCer-rich gel phase domains. This observation is tentatively attributed to differences in the presentation of the GalCer epitope in the two phases, resulting in differences in availability of the ligand for antibody binding. The complementary information obtained by swiftly switching between SEEC and fluorescence (including TIR fluorescence) imaging modes was used to support the data interpretation. The simplicity and generic applicability of the concept is discussed in terms of microfluidic applications.
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| 3. |
- Höök, Fredrik, 1966, et al.
(författare)
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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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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:2
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Feuz, Laurent, 1975, et al.
(författare)
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Improving the Limit of Detection of Nanoscale Sensors by Directed Binding to High-Sensitivity Areas
- 2010
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 4:4, s. 2167-2177
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Tidskriftsartikel (refereegranskat)abstract
- The revelation of protein protein-interactions is one of the main preoccupations in the field of proteomics. Nanoplasmonics has emerged as an attractive surface-based technique because of its ability to sense protein binding under physiological conditions in a label-free manner. Here, we use short-range ordered holes with a diameter of similar to 150 nm and a depth of similar to 50 nm as a nanoplasmonic template. A similar to 40 nm high cylindrical region of Au is exposed on the walls of the holes only, while the rest of the surface consists of TiO2. Since the sensitivity is confined to the nanometric holes, the use of two different materials for the sensor substrate offers the opportunity to selectively bind proteins to the most sensitive Au regions on the sensor surface. This was realized by applying material-selective poly(ethylene glycol)-based surface chemistry, restricting NeutrAvidin binding to surface-immobilized biotin on the Au areas only. We show that under mass-transport limited conditions (low nM bulk concentrations), the initial time-resolved response of uptake could be increased by a factor of almost 20 compared with the case where proteins were allowed to bind on the entire sensor surface and stress the generic relevance of this concept for nanoscale sensors. In the scope of further optimizing the limit of detection (LOD) of the sensor structure, we present finite-element (FE) simulations to unravel spatially resolved binding rates. These revealed that the binding rates in the holes occur in a highly inhomogeneous manner with highest binding rates observed at the upper rim of the holes and the lowest rates observed at the bottom of the holes. By assuming a plasmonic field distribution with enhanced sensitivity at the Au-TiO(2)interface, the FE simulations reproduced the experimental findings qualitatively.
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| 5. |
- Gunnarsson, Anders, 1981, et al.
(författare)
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Kinetic and thermodynamic characterization of single-mismatch discrimination using single-molecule imaging
- 2009
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 37:14, s. e99 (art no)-
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Gunnarsson, Anders, 1981, et al.
(författare)
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Kinetics of Ligand Binding to Membrane Receptors from Equilibrium Fluctuation Analysis of Single Binding Events
- 2011
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 133:38, s. 14852-14855
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Tidskriftsartikel (refereegranskat)abstract
- Equilibrium fluctuation analysis of single binding events has been used to extract binding kinetics of ligand interactions with cell-membrane bound receptors. Time-dependent total internal reflection fluorescence (TIRF) imaging was used to extract residence-time statistics of fluorescently stained liposomes derived directly from cell membranes upon their binding to surface-immobilized antibody fragments. The dissociation rate constants for two pharmaceutical relevant antibodies directed against different B-cell expressed membrane proteins was clearly discriminated, and the affinity of the interaction could be determined by inhibiting the interaction with increasing concentrations of soluble antibodies. The single-molecule sensitivity made the analysis possible without overexpressed membrane proteins, which makes the assay attractive in early drug-screening applications.
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| 7. |
- Jonsson, Magnus, 1981, et al.
(författare)
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Nanoplasmonic biosensing with focus on short-range ordered nanoholes in thin metal films
- 2008
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Ingår i: Biointerphases. - : American Vacuum Society. - 1559-4106 .- 1934-8630. ; 3:3, s. FD30-FD40
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Tidskriftsartikel (refereegranskat)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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| 8. |
- Jönsson, Daniel, 1984-, et al.
(författare)
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Inviwo - A Visualization System with Usage Abstraction Levels
- 2020
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Ingår i: IEEE Transactions on Visualization and Computer Graphics. - : IEEE. - 1077-2626 .- 1941-0506. ; 26:11, s. 3241-3254
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Tidskriftsartikel (refereegranskat)abstract
- The complexity of todays visualization applications demands specific visualization systems tailored for the development of these applications. Frequently, such systems utilize levels of abstraction to improve the application development process, for insta
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| 9. |
- Jönsson, Peter, 1981, et al.
(författare)
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Accumulation and Separation of Membrane-Bound Proteins Using Hydrodynamic Forces
- 2011
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 83:2, s. 604-611
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Tidskriftsartikel (refereegranskat)abstract
- The separation of molecules residing in the cell membrane remains a largely unsolved problem in the fields of bioscience and biotechnology. We demonstrate how hydrodynamic forces can be used to both accumulate and separate membrane-bound proteins in their native state. A supported lipid bilayer (SLB) was formed inside a microfluidic channel with the two proteins streptavidin (SA) and cholera toxin (CT) coupled to receptors in the lipid bilayer. The anchored proteins were first driven toward the edge of the lipid bilayer by hydrodynamic forces from a flowing liquid above the SLB, resulting in the accumulation of protein molecules at the edge of the bilayer. After the concentration process, the bulk flow of liquid in the channel was reversed and the accumulated proteins were driven away from the edge of the bilayer. Each type of protein was found to move at a characteristic drift velocity, determined by the frictional coupling between the protein and the lipid bilayer, as well as the size and shape of the protein molecule. Despite having a similar molecular weight, SA and CT could be separated into monomolecular populations using this approach. The method also revealed heterogeneity among the CT-molecules, resulting in three subpopulations with different drift velocities. This was tentatively attributed to multivalent interactions between the protein and the monosialoganglioside G(M1) receptors in the lipid bilayer.
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| 10. |
- Jönsson, Peter, 1981, et al.
(författare)
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Sealing of Submicrometer Wells by a Shear-Driven Lipid Bilayer
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:5, s. 1900-1906
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Tidskriftsartikel (refereegranskat)abstract
- A supported lipid bilayer (SLB) was formed in a microfluidic channel by vesicle fusion. The SLB, formed on a flat part of the surface, was driven by the shear forces of a bulk flow above the SLB to a part of the surface with embedded submicrometer wells. When using a bulk solution with a pH of 9.5 the advancing lipid bilayer sealed the wells, creating free-spanning membranes, whereas at a pH of 8.0 the SLB instead followed the contour of the wells.
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