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  • 1.
    Berg, Kirsti
    et al.
    Norwegian University of Science and Technology, Trondheim, Norway.
    Ericsson, Madelene
    Umeå University, Sweden.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology. Norwegian University of Science and Technology, Trondheim, Norway.
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Biomedical Engineering.
    A High Precision Method for Quantitative Measurements of Reactive Oxygen Species in Frozen Biopsies2014In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 9, no 3Article in journal (Refereed)
    Abstract [en]

    Objective

    An electron paramagnetic resonance (EPR) technique using the spin probe cyclic hydroxylamine 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetr​amethylpyrrolidine(CMH) was introduced as a versatile method for high precision quantification of reactive oxygen species, including the superoxide radical in frozen biological samples such as cell suspensions, blood or biopsies.

    Materials and Methods

    Loss of measurement precision and accuracy due to variations in sample size and shape were minimized by assembling the sample in a well-defined volume. Measurement was carried out at low temperature (150 K) using a nitrogen flow Dewar. The signal intensity was measured from the EPR 1st derivative amplitude, and related to a sample, 3-carboxy-proxyl (CP•) with known spin concentration.

    Results

    The absolute spin concentration could be quantified with a precision and accuracy better than ±10 µM (k = 1). The spin concentration of samples stored at −80°C could be reproduced after 6 months of storage well within the same error estimate.

    Conclusion

    The absolute spin concentration in wet biological samples such as biopsies, water solutions and cell cultures could be quantified with higher precision and accuracy than normally achievable using common techniques such as flat cells, tissue cells and various capillary tubes. In addition; biological samples could be collected and stored for future incubation with spin probe, and also further stored up to at least six months before EPR analysis, without loss of signal intensity. This opens for the possibility to store and transport incubated biological samples with known accuracy of the spin concentration over time.

  • 2.
    Bogoeva, Vanya
    et al.
    Bulgarian Academic Science, Bulgaria.
    Siksjö, Monica
    Norwegian University of Science and Technology, Norway.
    Säterbo, Kristin G.
    Norwegian University of Science and Technology, Norway.
    Melo, Thor Bernt
    Norwegian University of Science and Technology, Norway.
    Björköy, Astrid
    Norwegian University of Science and Technology, Norway.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Norwegian University of Science and Technology, Norway.
    Gederaas, Odrun A.
    Norwegian University of Science and Technology, Norway.
    Ruthenium porphyrin-induced photodamage in bladder cancer cells2016In: Photodiagnosis and Photodynamic Therapy, ISSN 1572-1000, E-ISSN 1873-1597, Vol. 14Article in journal (Refereed)
    Abstract [en]

    Photodynamic therapy (PDT) is a noninvasive treatment for solid malignant and flat tumors. Light activated sensitizers catalyze photochemical reactions that produce reactive oxygen species which can cause cancer cell death. In this work we investigated the photophysical properties of the photosensitizer ruthenium(II) porphyrin (RuP), along with its PDT efficiency onto rat bladder cancer cells (AY27). Optical spectroscopy verified that RuP is capable to activate singlet oxygen via blue and red absorption bands and inter system crossing (ISC) to the triplet state. In vitro experiments on AY27 indicated increased photo-toxicity of RuP (20 mu M, 1811 incubation) after cell illumination (at 435 nm), as a function of blue light exposure. Cell survival fraction was significantly reduced to 14% after illumination of 20 mu M RuP with 15.6 J/cm(2), whereas the "dark toxicity" of 20 mu M RuP was 17%. Structural and morphological changes of cells were observed, due to RuP accumulation, as well as light-dependent cell death was recorded by confocal microscopy. Flow cytometry verified that PDT-RuP (50 mu M) triggered significant photo-induced cellular destruction with a photoxicity of (93% +/- 0.9%). Interestingly, the present investigation of RuP-PDT showed that the dominating mode of cell death is necrosis. RuP "dark toxicity" compared to the conventional chemotherapeutic drug cisplatin was higher, both evaluated by the MIT assay (24 h). In conclusion, the present investigation shows that RuP with or without photoactivation induces cell death of bladder cancer cells. (C) 2016 Elsevier B.V. All rights reserved.

  • 3.
    Carlsson, Karin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Persson, Egon
    Haemostasis Biochemistry, Novo Nordisk A/S, DK-2760 Måløv, Denmark.
    Østergaard, Henrik
    Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Carlsson, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Svensson, Magdalena
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Effects on the conformation of FVIIa by sTF and Ca(2+) binding: Studies of fluorescence resonance energy transfer and quenching2011In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 413, no 4, p. 545-549Article in journal (Refereed)
    Abstract [en]

    The apparent length of FVIIa in buffer solution was estimated by a FRET analysis. Two fluorescent probes, fluorescein linked to an inhibitor (FPR-chloromethyl ketone) and a rhodamine derivative (tetramethylrhodamine-5-maleimide), were covalently attached to FVIIa. The binding site of fluorescein was in the PD whereas rhodamine was positioned in the Gla domain, thus allowing a length measure over approximately the whole extension of the protein. From the FRET measurements the distances between the two probes were determined to 61.4 for free FVIIa and 65.5 Å for FVIIa bound to the soluble TF (sTF). Thus, the apparent distance from the FRET analysis was shown to increase with 4 Å upon formation of a complex with sTF in solution. However, by considering how protein dynamics, based on recently published molecular dynamics simulations of FVIIa and sTF:FVIIa (Ohkubo et al., 2010 J. Thromb. Haemost. 8, 1044-1053), can influence the apparent  fluorescence signal our calculations indicated that the global average conformation of active-site inhibited FVIIa is nearly unaltered upon ligation to sTF.

    Moreover, it is known that Ca2+ binding leads to activation of FVIIa, and we have for the first time demonstrated conformational changes in the environment of the active site upon Ca2+ binding by direct measurements, previously suggested based on indirect measurements (Persson & Petersen, 1995 Eur. J. Biochem. 234, 293-300). Interestingly, this Ca2+-induced conformational change can be noted even in the presence of an inhibitor. By forming the sTF:FVIIa complex the conformational change of the active site is further developed, leading to a more inaccessible active-site located probe.

  • 4.
    Gustafsson, Håkan
    et al.
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Diagnostics, Department of Biomedical Engineering. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology. Norwegian University of Science and Technology, Norway.
    Kolbun, Natallia
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Jonson, Maria
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Engström, Maria
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    de Muinck, Ebo
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Region Östergötland, Heart and Medicine Center, Department of Cardiology in Linköping.
    Zachrisson, Helene
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Visualization of oxidative stress in ex vivo biopsies using electron paramagnetic resonance imaging2015In: Magnetic Resonance in Medicine, ISSN 0740-3194, E-ISSN 1522-2594, Vol. 73, no 4, p. 1682-1691Article in journal (Refereed)
    Abstract [en]

    PURPOSE: The purpose of this study was to develop an X-Band electron paramagnetic resonance imaging protocol for visualization of oxidative stress in biopsies.

    METHODS: The developed electron paramagnetic resonance imaging protocol was based on spin trapping with the cyclic hydroxylamine spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine and X-Band EPR imaging. Computer software was developed for deconvolution and back-projection of the EPR image. A phantom containing radicals of known spatial characteristic was used for evaluation of the developed protocol. As a demonstration of the technique electron paramagnetic resonance imaging of oxidative stress was performed in six sections of atherosclerotic plaques. Histopathological analyses were performed on adjoining sections.

    RESULTS: The developed computer software for deconvolution and back-projection of the EPR images could accurately reproduce the shape of a phantom of known spatial distribution of radicals. The developed protocol could successfully be used to image oxidative stress in six sections of the three ex vivo atherosclerotic plaques.

    CONCLUSIONS: We have shown that oxidative stress can be imaged using a combination of spin trapping with the cyclic hydroxylamine spin probe cyclic hydroxylamine spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine and X-Band EPR imaging. A thorough and systematic evaluation on different types of biopsies must be performed in the future to validate the proposed technique. Magn Reson Med, 2014.

  • 5.
    Lilledahl, Magnus B.
    et al.
    Norwegian University of Science and Technoogy, Norway.
    Gustafsson, Håkan
    Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences. Region Östergötland, Center for Diagnostics, Department of Biomedical Engineering.
    Gunnar Ellingsen, Pal
    Norwegian University of Science and Technoogy, Norway.
    Zachrisson, Helene
    Linköping University, Department of Medical and Health Sciences, Division of Cardiovascular Medicine. Linköping University, Faculty of Health Sciences. Region Östergötland, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Hallbeck, Martin
    Linköping University, Department of Clinical and Experimental Medicine, Division of Neuro and Inflammation Science. Linköping University, Faculty of Medicine and Health Sciences. Region Östergötland, Center for Diagnostics, Department of Clinical Pathology and Clinical Genetics.
    Stenhjem Hagen, Vegard
    Norwegian University of Science and Technoogy, Norway.
    Kildemo, Morten
    Norwegian University of Science and Technoogy, Norway.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology. Norwegian University of Science and Technoogy, Norway.
    Combined imaging of oxidative stress and microscopic structure reveals new features in human atherosclerotic plaques2015In: Journal of Biomedical Optics, ISSN 1083-3668, E-ISSN 1560-2281, Vol. 20, no 2, p. 020503-Article in journal (Refereed)
    Abstract [en]

    Human atherosclerotic samples collected by carotid endarterectomy were investigated using electronic paramagnetic resonance imaging (EPRI) for visualization of reactive oxygen species, and nonlinear optical microscopy (NLOM) to study structural features. Regions of strong EPRI signal, indicating a higher concentration of reactive oxygen species and increased inflammation, were found to colocalize with regions dense in cholesterol crystals as revealed by NLOM.

  • 6.
    Lindgren, Mikael
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Stabo-Eeg, Frantz
    Norwegian University of Science and Technology.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Biochemistry. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Biosensing and -imaging with enantiomeric luminescent conjugated polythiophenes using single - and multiphoton excitation2006In: Proceedings of International Symposium on Biophotonics, Nanophotonics and Metamaterials, IEEE , 2006, p. 226-226Conference paper (Refereed)
  • 7.
    Lunden, Hampus
    et al.
    Swedish Def Res Agcy FOI, Sensor & EW Syst, Linkoping, Sweden.
    Liotta, A.
    University of Lyon 1, France.
    Chateau, D.
    University of Lyon 1, France.
    Lerouge, F.
    University of Lyon 1, France.
    Chaput, F.
    University of Lyon 1, France.
    Parola, S.
    University of Lyon 1, France.
    Brannlund, C.
    Swedish Def Research Agency FOI, Sensor and EW Syst, SE-58111 Linkoping, Sweden.
    Ghadyani, Z.
    Norwegian University of Science and Technology, Norway.
    Kildemo, M.
    Norwegian University of Science and Technology, Norway.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology. Norwegian University of Science and Technology, Norway.
    Lopes, C.
    Swedish Def Research Agency FOI, Sensor and EW Syst, SE-58111 Linkoping, Sweden.
    Dispersion and self-orientation of gold nanoparticles in sol-gel hybrid silica - optical transmission properties2015In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 3, no 5, p. 1026-1034Article in journal (Refereed)
    Abstract [en]

    Silica-based hybrid materials doped with gold nanoparticles (AuNPs) of different shapes were prepared with an adapted sol-gel technology (using MTEOS) and polished to high optical quality. Both spherical (23 and 45 nm in diameter) and bipyramidal (36, 50 and 78 nm in length) AuNPs were prepared and used as dopants. The AuNPs were functionalized with a novel silicone polymer for compatibilization with the sol-gel medium. The glass materials showed well defined localized surface plasmon resonance (SPR) absorbance from the visible to NIR. No redshifts in the spectra, due to the increase in doping concentration, were observed in the glasses, proving that no or very small SPR coupling effects occur. Spectroscopic Muller Matrix Ellipsometry showed that the shorter bipyramidal AuNPs (36 and 50 nm in length) have a clear preferred orientation in the MTEOS matrix, i.e. a tendency to be oriented with their long axis in the plane parallel to the glass surfaces. Dispersions of AuNPs have proven to be good optical power limiters that depend on particle size and geometry. The solid-state glass materials showed good optical power limiting at 532 nm for nanosecond pulses, which did not depend on the size or geometry of the AuNPs. In contrast to the observation at 532 nm, at 600 nm no optical limiting effect was observed. In these solids, as for dispersions of AuNPs, the optical limiting response is caused by scattering.

  • 8.
    Lundén, H.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering. Electrooptical Systems, Swedish Defence Research Agency (FOI), Linköping, Sweden.
    Lopes, Cesar
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
    Liotta, A.
    Laboratoire de Chimie, ENS de Lyon, Lyon, France.
    Chateau,, D.
    Laboratoire de Chimie, ENS de Lyon, Lyon, France.
    Lerouge,, F.
    Laboratoire de Chimie, ENS de Lyon, Lyon, France.
    Chaput,, F.
    Laboratoire de Chimie, ENS de Lyon, Lyon, France.
    Désert,, A.
    Laboratoire de Chimie, ENS de Lyon, Lyon, France.
    Parola,, S.
    Laboratoire de Chimie, ENS de Lyon, Lyon, France.
    Efficient reverse saturable absorption of sol-gel hybrid plasmonic glasses2017In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 69, p. 134-140Article in journal (Refereed)
    Abstract [en]

    Monolithic silica sol-gel glasses doped with platinum(II) acetylide complexes possessing respectively four or six phenylacetylene units (PE2-CH2OH and PE3-CH2OH) in combination with various concentrations of spherical and bipyramidal gold nanoparticles (AuNPs) known to enhance non-linear optical absorption, were prepared and polished to high optical quality. The non-linear absorption of the glasses was measured and compared to glasses doped solely with AuNPs, a platinum(II) acetylide with shorter delocalized structure, or combinations of both. At 532 nm excitation wavelength the chromophore inhibited the non-linear scattering previously found for glasses only doped with AuNPs. The measured non-linear absorption was attributed to reverse saturable absorption from the chromophore, as previously reported for PE2-CH2OH/AuNP glasses. At 600 nm strong nonlinear absorption was observed for the PE3-CH2OH/AuNPs glasses, also attributed to reverse saturable absorption. But contrary to previous findings for PE2-CH2OH/AuNPs, no distinct enhancement of the non-linear absorption for PE3-CH2OH/AuNPs was observed. A numerical population model for PE3-CH2OH was used to give a qualitative explanation of this difference. A stronger linear absorption in PE3-CH2OH would cause the highly absorbing triplet state to populate quicker during the leading edge of the laser pulse and this would in turn reduce the influence from two-photon absorption enhancement from AuNPs.

  • 9.
    Lundén, Hampus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Glimsdal, Eirik
    Norwegian Def Res Estab FFI, Norway; Norwegian Univ Sci and Technol NTNU, Norway.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Norwegian Univ Sci and Technol NTNU, Norway.
    Lopes, Cesar
    Swedish Def Res Agcy, FOI, Linkoping, Sweden.
    How to assess good candidate molecules for self-activated optical power limiting2018In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303, Vol. 57, no 3, article id 030802Article in journal (Refereed)
    Abstract [en]

    Reverse saturable absorbers have shown great potential to attenuate laser radiation. Good candidate molecules and various particles have successfully been incorporated into different glass matrices, enabling the creation of self-activated filters against damaging laser radiation. Although the performance of such filters has been impressive, work is still ongoing to improve the performance in a wider range of wavelengths and pulse widths. The purpose of this tutorial is, from an optical engineering perspective, to give an understanding of the strengths and weaknesses of this class of smart materials, how relevant photophysical parameters are measured and influence system performance and comment on the pitfalls in experimental evaluation of materials. A numerical population model in combination with simple physical formulas is used to demonstrate system behavior from a performance standpoint. Geometrical reasoning shows the advantage of reverse saturable absorption over nonlinear scattering due to a fraction of scattered light being recollected by imaging system optics. The numerical population model illustrates the importance of the optical power limiting performance during the leading edge of a nanosecond pulse, which is most strongly influenced by changes in the two-photon absorption cross section and the triplet linear absorption cross section for a modeled Pt-acetylide. This tutorial not only targets optical engineers evaluating reverse saturable absorbing materials but also aims to assist researchers with a chemistry background working on optical power limiting materials. We also present photophysical data for a series of coumarins that can be useful for the determination of quantum yields and two-photon cross sections and show examples of characterization of molecules with excited triplet states. (c) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).

  • 10.
    Nilsson, Peter
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Hammarstrom, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    A pentameric luminescent-conjugated oligothiophene for optical imaging of in vitro-formed amyloid fibrils and protein aggregates in tissue sections.2012In: Methods in molecular biology (Clifton, N.J.), ISSN 1940-6029, Vol. 849, p. 425-434Article in journal (Refereed)
    Abstract [en]

    Luminescent-conjugated oligo- and polythiophenes (LCOs and LCPs) are valuable tools for optical imaging of a plethora of protein aggregates associated with amyloidoses. Here, we describe the utilization of an anionic pentameric LCO, p-FTAA, for staining of protein aggregates in a variety of platforms, including in vitro-formed amyloid fibrils and tissue sections.

  • 11.
    Nilsson, Peter
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Department of Physics, The Norwegian University of Science and Technology, 7491, Trondheim, Norway.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Luminescent-Conjugated Oligothiophene Probe Applications for Fluorescence Imaging of Pure Amyloid Fibrils and Protein Aggregates in Tissues2018In: Amyloid Proteins: Methods and Protocols / [ed] Einar M. Sigurdsson, Miguel Calero and María Gasset, Humana Press, 2018, Vol. 1779, p. 485-496Chapter in book (Refereed)
    Abstract [en]

    Luminescent-conjugated oligo- and polythiophenes (LCOs and LCPs) are valuable tools for optical imaging of a plethora of protein aggregates associated with amyloidoses. Here, we outline updated protocols for the application of the anionic pentameric LCO, p-FTAA, for staining and hyperspectral imaging of protein aggregates in a variety of settings such as in vitro formed amyloid fibrils, ex vivo tissue sections, and whole brain Drosophila.

  • 12.
    Nyström, Sofie
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Psonka-Antonczyk, Katarzyna M.
    Norwegian University of Science and Technology, Norway .
    Ellingsen, Pal Gunnar
    Norwegian University of Science and Technology, Norway .
    Johansson, Leif
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Reitan, Nina
    Norwegian University of Science and Technology, Norway .
    Handrick, Susann
    University of Medical Berlin, Germany .
    Prokop, Stefan
    University of Medical Berlin, Germany .
    Heppner, Frank L.
    University of Medical Berlin, Germany .
    Wegenast-Braun, Bettina M.
    German Centre Neurodegenerat Disease, Germany .
    Jucker, Mathias
    German Centre Neurodegenerat Disease, Germany .
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Torger Stokke, Bjorn
    Norwegian University of Science and Technology, Norway .
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Nilsson, Peter K R.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Evidence for Age-Dependent in Vivo Conformational Rearrangement within A beta Amyloid Deposits2013In: ACS Chemical Biology, ISSN 1554-8929, E-ISSN 1554-8937, Vol. 8, no 6, p. 1128-1133Article in journal (Refereed)
    Abstract [en]

    Deposition of aggregated A beta peptide in the brain is one of the major hallmarks of Alzheimers disease. Using a combination of two structurally different, but related, hypersensitive fluorescent amyloid markers, LCOs, reporting on separate ultrastructural elements, we show that conformational rearrangement occurs within A beta plaques of transgenic mouse models as the animals age. This important mechanistic insight should aid the design and evaluation of experiments currently using plaque load as readout.

  • 13.
    Psonka-Antonczyk, Katarzyna M.
    et al.
    Department of Physics, Norwegian University of Science and Technology NTNU, Trondheim, Norway.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Johansson, Leif
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemistry.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Department of Physics, Norwegian University of Science and Technology NTNU, Trondheim, Norway.
    Stokke, Björn T.
    Department of Physics, Norwegian University of Science and Technology NTNU, Trondheim, Norway.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Nyström, Sofie
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Nanoscale Structure and Spectroscopic Probing of A beta 1-40 Fibril Bundle Formation2016In: Frontiers in Chemistry, E-ISSN 2296-2646, Vol. 4, article id 44Article in journal (Refereed)
    Abstract [en]

    Amyloid plaques composed of fibrillar Amyloid-beta (A beta) are hallmarks of Alzheimers disease. However, A beta fibrils are morphologically heterogeneous. Conformation sensitive luminescent conjugated oligothiophenes (LCOs) are versatile tools for monitoring such fibril polymorphism in vivo and in vitro. Biophysical methods applied on in vitro generated A beta fibrils, stained with LCOs with different binding and fluorescence properties, can be used to characterize the A beta fibrillation in depth, far beyond that possible for in vivo generated amyloid plaques. In this study, in vitro fibrillation of the A beta 1-40 peptide was monitored by time-lapse transmission electron microscopy, LCO fluorescence, and atomic force microscopy. Differences in the LCO binding in combination with nanoscale imaging revealed that spectral variation correlated with fibrils transforming from solitary filaments (empty set similar to 2.5 nm) into higher order bundled structures (empty set similar to 5 nm). These detailed in vitro experiments can be used to derive data that reflects the heterogeneity of in vivo generated A beta plaques observed by LCO fluorescence. Our work provides new structural basis for targeted drug design and molecular probe development for amyloid imaging.

  • 14.
    Shirani, Hamid
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Sigurdson, Christina J.
    University of Calif San Diego, CA 92093 USA.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    A Palette of Fluorescent Thiophene-Based Ligands for the Identification of Protein Aggregates2015In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 43, p. 15133-15137Article in journal (Refereed)
    Abstract [en]

    By replacing the central thiophene unit of an anionic pentameric oligothiophene with other heterocyclic moities, a palette of pentameric thiophene-based ligands with distinct fluorescent properties were synthesized. All ligands displayed superior selectivity towards recombinant amyloid fibrils as well as disease-associated protein aggregates in tissue sections.

  • 15.
    Simon, Rozalyn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Bäck, Marcus
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Shirani, Hamid
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Nilsson, Peter R
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    pH-dependent optical transitions in anionic pentameric oligothiophenes2014Manuscript (preprint) (Other academic)
    Abstract [en]

    Understanding the photo-physical processes in fluorescent probes are essential as such dyes are widely utilized in molecular biology. Here we report the pH-dependent optical transitions of a library of anionic pentameric luminescent conjugated oligothiophenes (LCOs) that have been used for fluorescent identification of protein aggregates, the pathological hallmark of many devastating diseases. Absorption-, excitation- and emission spectra were recorded for all LCOs in different buffers with a pH range from 3.5 to 7. p-FTAA, a LCO having a central core consisting of a trimeric thiophene  building block with head-to-head acetic acid functionalization as well as terminal carboxyl groups extending the pentameric thiophene backbone, displayed pH/dependent optical characteristics correlating to a non-planar to planar transition of the conjugated backbone as well as aggregation between adjacent thiophene chain upon protonation of the  acetic acid side chains. In contrast, chemically related analogues to p-FTAA lacking the  terminal carboxyl groups extending the pentameric thiophene backbone or the conformational ability to undergo a non/planar to planar transition of the  conjugated backbone, displayed different optical characteristics compared to p-FTAA. Overall these studies highlighted that minor chemical alteration of LCOs can result in major difference in the optical characteristics obtained from the dyes and the results might aid in designing novel LCOs that have  superior optical performance as amyloid ligands.

  • 16.
    Sjöqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Molecular dynamics effects on luminescence properties of oligothiophene derivatives: a molecular mechanics-response theory study based on the CHARMM force field and density functional theory2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 39, p. 17532-17542Article in journal (Refereed)
    Abstract [en]

    CHARMM force field parameter values for a class of oligothiophene derivatives have been derived with reference to density functional theory/B3LYP potential energy surfaces. The force field parametrization of these luminescent conjugated polyelectrolytes includes the electronic ground state as well as the strongly light absorbing first excited state. In conjunction with quantum chemical response theory calculations of transition state properties, a molecular dynamical model of the Stokes shift is obtained. The theoretical model is benchmarked against experimental data recorded at room temperature which refer to sodium salts of p-HTAA and p-FTAA with distilled water as a solvent. For p-HTAA the theoretically predicted Stokes shift of 112 nm is in good agreement with the experimental result of 124 nm, given the approximations about exciton localization that were introduced to obtain a force field for the excited state.

  • 17.
    Sjöqvist, Jonas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Maria, Jerôme
    Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
    Simon, Rozalyn
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology. Department of Physics, Norwegian University of Science and Technology, Trondheim, Norway.
    Toward a molecular understanding of the detection of amyloid proteins with flexible conjugated oligothiophenes2014In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 118, no 42, p. 9820-9827Article in journal (Refereed)
    Abstract [en]

    Molecular and electronic structures and optical absorption properties of oligothiophenes used for spectral assignment of amyloid deposits have been investigated for a family of probes known as luminescent conjugated oligothiophenes (LCOs). Theoretical absorption spectra have been determined using conformational averaging, combining classical molecular dynamics (MD) simulations with quantum mechanical/molecular mechanics (QM/MM) time-dependent density functional theory (TD-DFT) spectrum calculations. Theoretical absorption spectra are in excellent agreement with experiments, showing average errors below 5 nm for absorption maxima. To couple observed properties to molecular structures, a measure of planarity is defined, revealing a strong correlation between the transition wavelength of the first and dominating electronically excited state and dihedral rotations. It is shown that from this correlation, predictions can be made of the absorption properties of probes based only on information from MD trajectories. We show experimentally that red shifts observed in the excitation maxima of LCOs when bound to amyloid protein aggregates are also evident in absorption spectra. We predict that these red shifts are due to conformational restriction of the LCO in a protein binding pocket, causing a planarization of the conjugated backbone. On the basis of our studies of planarity, it is shown that such shifts are both possible and realistic.

  • 18.
    Zhang, Jun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Sandberg, Alexander
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Konsmo, Audun
    Norwegian Univ Sci and Technol, Norway.
    Wu, Xiongyu
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Nyström, Sofie
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Nilsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    LeVine, Harry III
    Univ Kentucky, KY 40536 USA.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Norwegian Univ Sci and Technol, Norway.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Detection and Imaging of A beta 1-42 and Tau Fibrils by Redesigned Fluorescent X-34 Analogues2018In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 24, no 28, p. 7210-7216Article in journal (Refereed)
    Abstract [en]

    We revisited the Congo red analogue 2,5-bis(4-hydroxy-3-carboxy-styryl)benzene (X-34) to develop this highly fluorescent amyloid dye for imaging Alzheimers disease (AD) pathology comprising A beta and Tau fibrils. A selection of ligands with distinct optical properties were synthesized by replacing the central benzene unit of X-34, with other heterocyclic moieties. Full photophysical characterization was performed, including recording absorbance and fluorescence spectra, Stokes shift, quantum yield and fluorescence lifetimes. All ligands displayed high affinity towards recombinant amyloid fibrils of A beta 1-42 (13-300nmK(d)) and Tau (16-200nmK(d)) as well as selectivity towards the corresponding disease-associated protein aggregates in AD tissue. We observed that these ligands efficiently displaced X-34, but not Pittsburgh compound B (PiB) from recombinant A beta 1-42 amyloid fibrils, arguing for retained targeting of the Congo red type binding site. We foresee that the X-34 scaffold offers the possibility to develop novel high-affinity ligands for A pathology found in human AD brain in a different mode compared with PiB, potentially recognizing different polymorphs of A fibrils.

  • 19.
    Zhang, Jun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Chemistry.
    Sandberg, Alexander
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Wu, Xiongyu
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Nyström, Sofie
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Lindgren, Mikael
    Department of Physics, The Norwegian University of Science and Technology, Trondheim, Norway.
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    trans-Stilbenoids with Extended Fluorescence Lifetimes for the Characterization of Amyloid Fibrils2017In: ACS Omega, ISSN 2470-1343, Vol. 2, no 8, p. 4693-4704Article in journal (Refereed)
    Abstract [en]

    It was previously reported that two naphthyl-based trans-stilbene probes, (E)-4-(2-(naphthalen-1-yl)vinyl)benzene-1,2-diol (1) and (E)-4-(2-(naphthalen-2-yl)vinyl)benzene-1,2-diol (3), can bind to both native transthyretin (TTR) and misfolded protofibrillar TTR at physiological concentrations, displaying distinct emission maxima bound to the different conformational states (>100 nm difference). To further explore this amyloid probe scaffold to obtain extended fluorescence lifetimes, two new analogues with expanded aromatic ring systems (anthracene and pyrene), (E)-4-(2-(anthracen-2-yl)vinyl)benzene-1,2-diol (4) and (E)-4-(2-(pyren-2-yl)vinyl)benzene-1,2-diol (5), were synthesized employing the palladium-catalyzed Mizoroki–Heck reaction. (E)-4-Styrylbenzene-1,2-diol (2), 3, 4, and 5 were investigated with respect to their photophysical properties in methanol and when bound to insulin, lysozyme, and Aβ1-42 fibrils, including time-resolved fluorescence measurements. In conclusion, 4 and 5 can bind to both native and fibrillar TTR, becoming highly fluorescent. Compounds 2–5 bind specifically to insulin, lysozyme, and Aβ1-42 fibrils with an apparent fluorescence intensity increase and moderate binding affinities. The average fluorescence lifetimes of the probes bound to Aβ1-42 fibrils are 1.3 ns (2), 1.5 ns (3), 5.7 ns (4), and 29.8 ns (5). In summary, the variable aromatic moieties of the para-positioned trans-stilbenoid vinyl-benzene-1,2-diol with benzene, naphthalene, anthracene, and pyrene showed that the extended conjugated systems retained the amyloid targeting properties of the probes. Furthermore, both the anthracene and pyrene moieties extensively enhanced the fluorescence intensity and prolonged lifetimes. These attractive probe properties should improve amyloid detection and characterization by fluorescence-based techniques.

  • 20.
    Zhang, Jun
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Wang, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Bioinformatics. Linköping University, Faculty of Science & Engineering.
    Sandberg, Alexander
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Wu, Xiongyu
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Nyström, Sofie
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    LeVine, Harry III
    Sanders-Brown Center on Aging, University of Kentucky, KY 40536-0230, Lexington, USA..
    Konradsson, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Hammarström, Per
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Durbeej, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Bioinformatics. Linköping University, Faculty of Science & Engineering.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering. Department of Physics, Norwegian University of Science and Technology, 7491, Trondheim, Norway..
    Intramolecular Proton and Charge Transfer of Pyrene-based trans-Stilbene Salicylic Acids Applied to Detection of Aggregated Proteins.2018In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 19, no 22, p. 3001-3009Article in journal (Refereed)
    Abstract [en]

    Two analogues to the fluorescent amyloid probe 2,5-bis(4'-hydroxy-3'-carboxy-styryl)benzene (X-34) were synthesized based on the trans-stilbene pyrene scaffold (Py1SA and Py2SA). The compounds show strikingly different emission spectra when bound to preformed Aβ1-42 fibrils. This remarkable emission difference is retained when bound to amyloid fibrils of four distinct proteins, suggesting a common binding configuration for each molecule. Density functional theory calculations show that Py1SA is twisted, while Py2SA is more planar. Still, an analysis of the highest occupied molecular orbitals (HOMOs) and lowest unoccupied molecular orbitals (LUMOs) of the two compounds indicates that the degree of electronic coupling between the pyrene and salicylic acid (SA) moieties is larger in Py1SA than in Py2SA. Excited state intramolecular proton transfer (ESIPT) coupled-charge transfer (ICT) was observed for the anionic form in polar solvents. We conclude that ICT properties of trans-stilbene derivatives can be utilized for amyloid probe design with large changes in emission spectra and decay times from analogous chemical structures depending on the detailed physical nature of the binding site.less thanbr /greater than (© 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.)

  • 21.
    Örtegren, Jonas
    et al.
    Department of Polymer Technology, Royal Institute of Technology, Stockholm, Sweden.
    Andersson, Gunnar
    Physics Department, Chalmers University of Technology, Göteborg, Sweden.
    Busson, Philippe
    Department of Polymer Technology, Royal Institute of Technology, Stockholm, Sweden.
    Hult, Anders
    Department of Polymer Technology, Royal Institute of Technology, Stockholm, Sweden.
    Gedde, Ulf W.
    Department of Polymer Technology, Royal Institute of Technology, Stockholm, Sweden.
    Eriksson, Anders
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Health Sciences.
    Lindgren, Mikael
    National Defence Research Establishment, Linköping, Sweden.
    Improved thermal stability of pyroelectric polymers by crosslinking of ferroelectric liquid crystals2001In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 105, no 42, p. 10223-10227Article in journal (Refereed)
    Abstract [en]

    Monofunctional ferroelectric liquid crystalline monomers and a blend of monofunctional/bifunctional ferroelectric liquid crystalline monomers were photopolymerized, yielding a side-chain liquid crystalline polymer and a cross-linked polymer, respectively. The cross-linked polymer exhibited higher thermal stability than the side-chain liquid crystalline polymer and was pyroelectric up to 170 °C, whereas the side-chain liquid crystalline polymer lost most of its pyroelectricity at 38 °C. It is shown by electrooptic and birefringence measurements that cross-linking in the unwound SmC* phase prevented the reoccurrence of the helical superstructure.

  • 22.
    Örtegren, Jonas
    et al.
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Busson, Philippe
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Gedde, Ulf W.
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Hult, Anders
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Eriksson, Anders
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Andersson, Gunnas
    Physics Department, Chalmers University of Technology, Göteborg, Sweden.
    Cone motion viscosity and optical second harmonic generation of ferroelectric liquid crystalline dendrimers2001In: Liquid crystals (Print), ISSN 0267-8292, E-ISSN 1366-5855, Vol. 28, no 6, p. 861-868Article in journal (Refereed)
    Abstract [en]

    We report second harmonic generation in a ferroelectric liquid crystalline trimer and ferroelectric liquid crystalline dendrimers of first, second and third generation. Thin cells were filled with the compounds by capillary forces at elevated temperature, and cooled from the surface stabilized ferroelectric state to below the glass transition temperature, while kept in an electric field. The cone motion viscosity and the threshold electric field for unwinding of the helix axis of the chiral tilted smectic mesophases were studied separately at elevated temperature, and these data were used to optimize the preparation of the films. The measured response time was between 0.3 and 3ms, which corresponds to a cone motion viscosity between 0.5 and 50 Pa s. Second harmonic generation was studied both at elevated temperature with an electric field and at room temperature with and without electric field. The first generation dendrimer exhibited a strong increase in the second order non-linear optical response with time at room temperature. The d 23-coefficient of this dendrimer was approximately four times larger than for the other macromolecules and was 0.045 pm V-1. The relatively large d-coefficient of the first generation dendrimer is ascribed to crystallization, which improved the orientation of the molecular dipoles.

  • 23.
    Örtegren, Jonas
    et al.
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Busson, Philippe
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Gedde, Ulf W.
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Hult, Anders
    Department of Polymer Technology, Royal Institute of Technology, Sweden.
    Eriksson, Anders
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lindgren, Mikael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Arntzén, Per-Otto
    National Defence Research Establishment, Linköping, Sweden.
    Hermann, David S.
    Physics Department, Chalmers University of Technology,Göteborg, Sweden.
    Rudquist, Per
    Physics Department, Chalmers University of Technology,Göteborg, Sweden.
    Lagerwall, Sven T.
    Physics Department, Chalmers University of Technology,Göteborg, Sweden.
    Time-dependent nonlinear optical properties of pyroelectric liquid crystalline polymers1999In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 148, p. 179-195Article in journal (Refereed)
    Abstract [en]

    Highly oriented pyroelectric liquid-crystalline polymers were prepared by photopolymerization under the influence of a static electric field from binary mixtures of two acrylate monomers exhibiting chiral smectic C mesomorphism. Both monomers contained nitro groups to yield second order nonlinear optical properties (second harmonic generation) and one of the monomers had two functional groups to yield a crosslinked polymer. The room temperature second order nonlinear susceptibility of the polymers showed during the first two hours a 10 % decrease after which it remained constant during the next 48 days. At elevated temperatures there was a significant difference in the nonlinear optical properties over time between crosslinked and uncrosslinked polymers. The uncrosslinked polymer showed a pronounced loss of second order nonlinear optical activity with time at ≥38°C. The crosslinked polymer showed a much smaller and basically a temperature independent decrease rate in the second order nonlinear optical properties at all the ageing temperatures (23-130°C). Both the loss in mesogen order parameter, very evident for the uncrosslinked polymer, and conformational changes occurring within the mesogens (β mechanism), may account for the observations made.

1 - 23 of 23
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