| 1. |
- Fant, Camilla, et al.
(author)
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Investigation of Adsorption and Cross-Linking of a Mussel Adhesive Protein Using Attenuated Total Internal Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR)
- 2010
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In: Journal of Adhesion. - : Informa UK Limited. - 0021-8464 .- 1545-5823 .- 1563-518X. ; 86:1, s. 25-38
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Journal article (peer-reviewed)abstract
- Mytilus edulis foot protein 1 (Mefp-1) contains the redox-functional amino acid 3,4-dihydroxyphenylalanine (DOPA), which is a typical feature of most mefp proteins. We have previously shown, using combined optic (ellipsometry) and acoustic (QCM-D) measurements, that the oxidizing agent sodium periodate (NaIO4) and the transition metal ion Cu2+ promote cross-linking of Mefp-1. However, different chemical reaction mechanisms can not be distinguished using these methods. In the present study, we have complemented our previous investigations using Attenuated Total Internal Reflection Fourier Transform Infrared spectroscopy (ATR-FTIR), allowing a spectroscopic analysis of NaIO4 and Cu2+-induced cross-linking of Mefp-1 adsorbed on a ZnSe surface. In aqueous solution, adsorbed Mefp-1 displays absorption bands at 1570, 1472, 1260, and 973 cm(-1). Upon addition of NaIO4 and Cu2+, the absorptions at 1570, 1472, and 973 cm(-1) increase by approximately a factor of two. In contrast, the band at 1260 cm(-1) disappears upon cross-linking using NaIO4, but remains unchanged upon addition of Cu2+. This demonstrates that the band at 1260cm(-1) is attributed to the C O stretching vibration of the side chain hydroxyl groups in DOPA and that Cu2+ forms complexes with DOPA rather than transform it into an o-quinone. Moreover, upon addition of NaIO4 after cross-linking using Cu2+, the band at 1260cm(-1) disappears, indicating that the complex formation between DOPA and Cu2+ is reversed when DOPA is transformed into the o-quinone. These results demonstrate that NaIO4, which initiates a similar reaction to the naturally occurring enzyme catechol oxidase, contributes to the formation of di-DOPA cross-links. In contrast, the dominating contribution to the cross-linking from Cu2+, which is accumulated at high concentrations in the byssus thread of the blue mussel, is via complex formation between the metal and DOPA residues.
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| 2. |
- Brändén, Magnus, 1971, et al.
(author)
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Label-Free Measurements of Molecular Transport across Liposome Membranes using Evanescent-Wave Sensing
- 2008
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In: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 9:17, s. 2480-2485
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Journal article (peer-reviewed)abstract
- Pucker up! A novel approach enabling direct measurements of biomolecular transfer across lipid bilayer membranes, using surface plasmon resonance, is demonstrated. The figure shows the transfer of sucrose (S) through melittin pores formed in surface-attached liposomes. By measuring the shift in refractive index in the volume enclosed by the liposomes, the sucrose transfer can be time-resolved and quantified.
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| 3. |
- Brändén, Magnus, 1971, et al.
(author)
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Refractive-Index-Based Screening of Membrane-Protein-Mediated Transfer across Biological Membranes
- 2010
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In: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 99:1, s. 124-133
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Journal article (peer-reviewed)abstract
- Numerous membrane-transport proteins are major drug targets, and therefore a key ingredient in pharmaceutical development is the availability of reliable, efficient tools for membrane transport characterization and inhibition. Here, we present the use of evanescent-wave sensing for screening of membrane-protein-mediated transport across lipid bilayer membranes. This method is based on a direct recording of the temporal variations in the refractive index that occur upon a transfer-dependent change in the solute concentration inside liposomes associated to a surface plasmon resonance (SPR) active sensor surface. The applicability of the method is demonstrated by a functional study of the aquaglyceroporin PfAQP from the malaria parasite Plasmodium falciparum. Assays of the temperature dependence of facilitated diffusion of sugar alcohols on a single set of PfAQP-reconstituted liposomes reveal that the activation energies for facilitated diffusion of xylitol and sorbitol are the same as that previously measured for glycerol transport in the aquaglyceroporin of Escherichia coli (5 kcal/mole). These findings indicate that the aquaglyceroporin selectivity filter does not discriminate sugar alcohols based on their length, and that the extra energy cost of dehydration of larger sugar alcohols, upon entering the pore, is compensated for by additional hydrogen-bond interactions within the aquaglyceroporin pore.
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| 7. |
- Höök, Fredrik, 1966, et al.
(author)
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Quantitative Biological Surface Science: Challenges and Recent Advances
- 2008
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In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. ; 2:12, s. 2428-2436
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Journal article (peer-reviewed)abstract
- Biological surface science is a broad, interdisciplinary subfield of surface science, where properties and processes at biological and synthetic surfaces and interfaces are investigated, and where biofunctional surfaces are fabricated. The need to study and to understand biological surfaces and interfaces in liquid environments provides sizable challenges M, as well as fascinating opportunities. Here, we report on recent progress in biological surface E. science that was described within the program assembled by the Biomaterial Interface Division of the Science and Technology of Materials, Interfaces and Processes (www.avs.org) during their 55th International Symposium and Exhibition held in Boston, October 19-24, 2008. The selected examples show that the rapid progress in nanoscience and nanotechnology, hand-in-hand with theory and simulation, provides increasingly sophisticated methods and tools to unravel the mechanisms and details of complex processes at biological surfaces and in-depth understanding of biomolecular surface interactions.
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| 8. |
- 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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| 9. |
- 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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| 10. |
- Jonsson, Magnus, 1981, et al.
(author)
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Nanoplasmonic sensing combined with artificial cell membranes
- 2012
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In: Nanoplasmonic Sensors. - New York, NY : Springer New York. - 9781461439332 ; , s. 59-82
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Book chapter (other academic/artistic)abstract
- This chapter is dedicated to nanoplasmonic sensing systems made compatible with studies of artificial cell membranes. After a short motivation to the opportunity of sensors designed for such studies to fill an existing technological gap, we introduce basic features of cell membranes and common mimics of the cell membrane that have been proven useful in various bioanalytical sensing applications. With suitable examples from the literature, subsequent sections exemplify how nanoplasmonics can be used to study different reactions that are associated with cell membranes. In particular, focus is on unique possibilities provided by different types of nanoplasmonic structures. For example, while discrete nanoplasmonic particles can be used as mobile probes attached to cell membranes, conductive nanoplasmonic hole structures can be used for combined optical and electrical transduction. Examples on how the latter possibility has enabled cell membrane-related reactions to be investigated with nanoplasmonic sensing combined with quartz crystal microbalance with dissipation monitoring are presented. Another key aspect of nanoplasmonic structures is that the plasmonic field (and hence the refractive index sensitivity) is strongest at the sensor surface and decays rapidly away from the surface. We describe how this feature provides a means to monitor structural changes of molecules on the surface, such as the spontaneous rupture of lipid vesicles into a supported lipid bilayer on silicon oxide-coated nanoplasmonic holes.
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