| 1. |
- Björk, Per, et al.
(författare)
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Oligothiophene Assemblies Defined by DNA Interaction : From Single Chains to Disordered Clusters
- 2009
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Ingår i: SMALL. - : Wiley. - 1613-6810 .- 1613-6829. ; 5:1, s. 96-103
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Tidskriftsartikel (refereegranskat)abstract
- The organization of conjugated polyelectrolytes (CPEs) interacting with biomolecules sets conditions for the biodetection of biological processes and identity, through the use of optical emission from the CPE. Herein, a well-defined CPE and its binding to DNA is studied. By using dynamic light scattering and circular dichroism spectroscopy, it is shown that the CPE forms a multimolecule ensemble in aqueous solution that is more than doubled it? size when interacting with a small DNA chain, while single chains are evident in ethanol. The related changes in the fluorescence spectra upon polymer aggregation are assigned to oscillator strength redistribution between vibronic transitions in weakly coupled H-aggregates. An enhanced single-molecule spectroscopy technique that allows full control of excitation and emission light polarization is applied to combed and decorated;,DNA chains. It is found that the organization of combed CPE-lambda DNA complexes (when dry on the surface) allows considerable variation of CPE distances and direction relative to the DNA chain. By analysis of the polarization data. energy transfer between the polymer chains in individual complexes is confirmed and their sizes estimated.
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| 2. |
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| 3. |
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| 4. |
- Bäcklund, Fredrik, et al.
(författare)
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Amyloid fibrils as dispersing agents for oligothiophenes: control of photophysical properties through nanoscale templating and flow induced fibril alignment
- 2014
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428 .- 2050-7526 .- 2050-7534. ; 2:37, s. 7811-7822
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Tidskriftsartikel (refereegranskat)abstract
- Herein we report that protein fibrils formed from aggregated proteins, so called amyloid fibrils, serve as an excellent dispersing agent for hydrophobic oligothiophenes such as alpha-sexithiophene (6T). Furthermore, the protein fibrils are capable of orienting 6T along the fibril long axis, as demonstrated by flow-aligned linear dichroism spectroscopy and polarized fluorescence microscopy. The materials are prepared by solid state mixing of 6T with a protein capable of self-assembly. This results in a water soluble composite material that upon heating in aqueous acid undergoes self-assembly into protein fibrils non-covalently functionalized with 6T, with a typical diameter of 5-10 nm and lengths in the micrometre range. The resulting aqueous fibril dispersions are a readily available source of oligothiophenes that can be processed from aqueous solvent, and we demonstrate the fabrication of macroscopic structures consisting of aligned 6T functionalized protein fibrils. Due to the fibril induced ordering of 6T these structures exhibit polarized light emission.
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| 5. |
- Frykholm, Karolin, et al.
(författare)
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Probing Physical Properties of a DNA-Protein Complex Using Nanofluidic Channels
- 2014
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Ingår i: Biophysical Journal. - : Elsevier BV. - 0006-3495 .- 1542-0086. ; 106:2, s. 428A-429A
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Nanofluidic channels have become an important tool to investigate single DNA molecules both from a fundamental polymer physics perspective as well as in e.g. optical mapping techniques. However, less effort has been made to study DNA-protein complexes. A main reason is that the extreme surface-to-volume ratio in the nanochannels causes most proteins to stick to the channel walls. We have recently overcome this problem by coating the channels with a lipid bilayer, thereby eliminating sticking.
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| 6. |
- Frykholm, Karolin, 1977, et al.
(författare)
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Probing Physical Properties of a DNA- Protein Complex Using Nanofluidic Channels
- 2014
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 10:5, s. 884-887
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Tidskriftsartikel (refereegranskat)abstract
- A method to investigate physical properties of a DNA-protein complex in solution is demonstrated. By using tapered nanochannels and lipid passivation the persistence length of a RecA filament formed on double-stranded DNA is determined to 1.15 μm, in agreement with the literature, without attaching protein or DNA to any handles or surfaces.
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| 7. |
- Frykholm, Karolin, 1977, et al.
(författare)
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Probing physical properties of DNA-protein complexes using nanofluidic channels
- 2013
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Ingår i: 17th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2013; Freiburg; Germany; 27 October 2013 through 31 October 2013. - 9781632666246 ; 2, s. 1311-1313
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Konferensbidrag (refereegranskat)abstract
- We present the use of nanofluidic channels as a tool for determining physical properties of single DNA-protein complexes. By coating the nanochannels with a lipid bilayer we avoid sticking of proteins to the channel walls. RecA is a prokaryotic protein involved in recombination and DNA repair. We study filaments of RecA, bound to both double stranded (ds) and single stranded (ss) DNA. We determine the persistence length of RecA filaments on both dsDNA and ssDNA and obtain values in agreement with the literature. Neither the DNA nor the protein has to be attached to handles or surfaces, and the technique is directly transferable to Lab-on-a-Chip technologies for high throughput measurements in solution.
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| 8. |
- Hamedi, Mahiar, et al.
(författare)
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Polypeptide-guided assembly of conducting polymer nanocomposites
- 2010
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Ingår i: NANOSCALE. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 2:10, s. 2058-2061
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Tidskriftsartikel (refereegranskat)abstract
- A strategy for fabrication of electroactive nanocomposites with nanoscale organization, based on self-assembly, is reported. Gold nanoparticles are assembled by a polypeptide folding-dependent bridging. The polypeptides are further utilized to recruit and associate with a water soluble conducting polymer. The polymer is homogenously incorporated into the nanocomposite, forming conducting pathways which make the composite material highly conducting.
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| 9. |
- Hamedi, Mahiar, et al.
(författare)
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Synthetic Polypeptides as Scaffolds for Supramolecular Assembly of Conducting Polymer Nanocomposites
- 2010
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The development of nanoelectronics has resulted in enormous advancements in fabrication techniques that have enabled massproduction of CMOS circuits with feature sizes below 45nm. There is a large interest in new methods to further push the size limits, lower the production costs and to facilitate the design of more advanced three-dimensional structures beyond today’s 2.5 dimensional architectures. Self-assembly is probably the most important scheme in this development and is currently applied to many different areas and classes of nanoelectronics. Self-assembly enables fabrication of structures well below 10 nm in feature size and allows for incorporation of novel nanomaterials, such as metallic and semiconducting nanoparticles with many interesting optical and electrical properties. The controlled self-assembly of electro-active nanocomposites is of great interest for the development of novel functional materials including biosensors, electrochromic/plasmonic hybrid devices, and polymer/nanoparticle-based memories.
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| 10. |
- Hevekerl, Heike, 1982-, et al.
(författare)
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Dark states in ionic oligothiophene bioprobes-evidence from fluorescence correlation spectroscopy and dynamic light scattering
- 2014
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 118:22, s. 5924--5933
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Tidskriftsartikel (refereegranskat)abstract
- Luminescent conjugated polyelectrolytes (LCPs) can upon interaction with biological macromolecules change their luminescent properties, and thereby serve as conformation- and interaction-sensitive biomolecular probes. However, to exploit this in a more quantitative manner, there is a need to better understand the photophysical processes involved. We report studies of the conjugated pentameric oligothiophene, derivative p-FTAA, which changes optical properties with different p-FTAA concentrations in aqueous buffers, and in a pH and oxygen saturation dependent manner. Using dynamic light scattering, luminescence spectroscopy and fluorescence correlation spectroscopy, we find evidence for a monomer dimer equilibrium, for the formation of large clusters of p-FTAA in aqueous environment, and can couple aggregation to changed emission properties of oligothiophenes. In addition, we observe the presence of at least two dark transient states, one presumably being a triplet state. Oxygen was found to statically quench the p-FTAA fluorescence but also to promote molecular fluorescence by quenching dark transient states of the p-FTAA molecules. Taken together, this study provides knowledge of fluorescence and photophysical features essential for applying p-FTAA and other oligothiophene derivatives for diagnostic purposes, including detection and staining of amyloid aggregates.
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