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Sökning: WAKA:ref > Inganäs Olle > Hammarström Per > Refereegranskat

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1.
  • Frantz, S.E.A., et al. (författare)
  • Quantum efficiency and two-photon absorption cross-section of conjugated polyelectrolytes used for protein conformation measurements with applications on amyloid structures
  • 2007
  • Ingår i: Chemical Physics. - 0301-0104. ; 336:2-3, s. 121-126
  • Tidskriftsartikel (refereegranskat)abstract
    • Amyloid diseases such as Alzheimer's and spongiform encephalopathies evolve from aggregation of proteins due to misfolding of the protein structure. Early disease handling require sophisticated but yet simple techniques to follow the complex properties of the aggregation process. Conjugated polyelectrolytes (CPEs) have shown promising capabilities acting as optical biological sensors, since they can specifically bind to polypeptides both in solution and in solid phase. The structural changes in biomolecules can be monitored by changes of the optical spectra of the CPEs, both in absorption and emission modes. Notably, the studied CPEs possess multi-photon excitation capability, making them potential for in vivo imaging using laser scanning microscopy. Aggregation of proteins depends on concentration, temperature and pH. The optical effect on the molecular probe in various environments must also be investigated if applied in these environments. Here we present the results of quantum efficiency and two-photon absorption cross-section of three CPEs: POMT, POWT and PTAA in three different pH buffer systems. The extinction coefficient and quantum efficiency were measured. POMT was found to have the highest quantum efficiency being approximately 0.10 at pH 2.0. The two-photon absorption cross-section was measured for POMT and POWT and was found to be more than 18-25 times and 7-11 times that of Fluorescein, respectively. We also show how POMT fluorescence can be used to distinguish conformational differences between amyloid fibrils formed from reduced and non-reduced insulin in spectrally resolved images recorded with a laser scanning microscope using both one- and two-photon excitation. © 2007 Elsevier B.V. All rights reserved.
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  • Herland, Anna, et al. (författare)
  • Synthesis of a regioregular zwitterionic conjugated oligoelectrolyte, usable as an optical probe for detection of amyloid fibril formation at acidic pH
  • 2005
  • Ingår i: Journal of the American Chemical Society. - 0002-7863. ; 127:7, s. 2317-2323
  • Tidskriftsartikel (refereegranskat)abstract
    • Changes of the optical properties of conjugated polyelectrolytes have been utilized to monitor noncovalent interactions between biomolecules and the conjugated polyelectrolytes in sensor applications. A regioregular, zwitterionic conjugated oligoelectrolyte was synthesized in order to create a probe with a defined set of optical properties and hereby facilitate interpretation of biomolecule−oligoelectrolyte interactions. The synthesized oligoelectrolyte was used at acidic pH as a novel optical probe to detect amyloid fibril formation of bovine insulin and chicken lysozyme. Interaction of the probe with formed amyloid fibrils results in changes of the geometry and the electronic structure of the oligoelectrolyte chains, which were monitored with absorption and emission spectroscopy.
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  • Nilsson, Peter, et al. (författare)
  • Conjugated polyelectrolytes : conformation-sensitive optical probes for detection of amyloid fibril formation
  • 2005
  • Ingår i: Biochemistry. - 0006-2960. ; 44:10, s. 3718-3724
  • Tidskriftsartikel (refereegranskat)abstract
    • The in vivo deposition of amyloid fibrils is a hallmark of many devastating diseases known as the amyloidoses. Amyloid formation in vitro may also complicate production of proteins in the biotechnology industry. Simple, sensitive, and versatile tools that detect the fibrillar conformation of amyloidogenic proteins are thus of great importance. We have developed a negatively charged conjugated polyelectrolyte that displays different characteristic optical changes, detected visually or by absorption and emission, depending on whether the protein with which it forms a complex is in its native state or amyloid fibril conformation. This simple, rapid, and novel methodology was applied here to two amyloidogenic proteins, insulin and lysozyme, and its validity for detection of their fibrillar conformation was verified by currently used methods such as circular dichroism, transmission electron microscopy, and Congo red absorption.
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  • Nilsson, Peter, et al. (författare)
  • Imaging distinct conformational states of amyloid-β fibrils in Alzheimer's disease using novel luminescent probes
  • 2007
  • Ingår i: ACS Chemical Biology. - 1554-8929. ; 2:8, s. 553-560
  • Tidskriftsartikel (refereegranskat)abstract
    • Using luminescent conjugated polyelectrolyte probes (LCPs), we demonstrate the possibility to distinguish amyloid-β 1-42 peptide (Aβ1-42) fibril conformations, by analyzing in vitro generated amyloid fibrils of Aβ1-42 formed under quiescent and agitated conditions. LCPs were then shown to resolve such conformational heterogeneity of amyloid deposits in vivo. A diversity of amyloid deposits depending upon morphology and anatomic location was illustrated with LCPs in frozen ex vivo brain sections from a transgenic mouse model (tg-APPswe) of Alzheimer's disease. Comparative LCP fluorescence showed that compact-core plaques of amyloid β precursor protein transgenic mice were composed of rigid dense amyloid. A more abundant form of amyloid plaque displayed morphology of a compact center with a protruding diffuse exterior. Surprisingly, the compact center of these plaques showed disordered conformations of the fibrils, and the exterior was composed of rigid amyloid protruding from the disordered center. This type of plaque appears to grow from more loosely assembled regions toward solidified amyloid tentacles. This work demonstrates how application of LCPs can prove helpful to monitor aggregate structure of in vivo formed amyloid deposits such as architecture, maturity, and origin.
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8.
  • Åslund, Andreas, et al. (författare)
  • Studies of luminescent conjugated polythiophene derivatives-Enhanced spectral discrimination of protein conformational states
  • 2007
  • Ingår i: Bioconjugate chemistry. - 1043-1802. ; 18:6, s. 1860-1868
  • Tidskriftsartikel (refereegranskat)abstract
    • Improved probes for amyloid fibril formation are advantageous for the early detection and better understanding of this disease-associated process. Here, we report a comparative study of eight luminescent conjugated polythiophene derivates (LCPs) and their discrimination of a protein (insulin) in the native or amyloid-like fibrillar state. For two of the LCPs, the synthesis is reported. Compared to their monomer-based analogues, trimer-based LCPs showed significantly better optical signal specificity for amyloid-like fibrils, seen from increased quantum yield and spectral shift. The trimer-based LCPs alone were highly quenched and showed little interaction with native insulin, as seen from analytical ultracentrifugation and insignificant spectral differences from the trimer-based LCP in buffered and native protein solution. Hence, the trimer-based LCPs showed enhanced discrimination between the amyloid-like fibrillar state and the corresponding native protein.
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