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  • 1.
    Opanasyuk, Oleg
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    A new approach to the analyses of fluorescence depolarisation experiments in the presence of electronic energy transport2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A new and general procedure is described for a detailed analysis of time-resolved fluorescence depolarisation data in the presence of electronic energy migration. An isotropic ensemble of bifluorophoric molecules (D1-R-D2) has been studied to demonstrate its utility. Intramolecular donor-donor energy migration occurs between the two donor groups (D), which are covalently connected to a rigid linker group (R). These groups undergo restricted reorientational motions with respect to the R group. The analysis of depolarisation data basically involves the search for best-fit parameters which describe the local reorienting motions, the interfluorophore D1-D2 distance, as well as the mutual orientations of the donors. For this, the analysis is partly performed in the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process has been described by using Monte Carlo simulations and an extended Förster theory. It is found that this theory provides the least time-consuming computational method. Since one-photon and two-photon excited fluorescence experiments can be applied for energy migration studies, a general and unified theoretical formulation is given.

    To exemplify the developed quantitative approach the depolarisation of the fluorescence in the presence of electronic energy migration within a bis-(9-anthrylmethylphosphonate) bisteroid molecule has been studied by time-resolved two-photon excited fluorescence depolarisation experiments. To solely obtain information about local reorientations of the 9-anthrylmethyl group, also the mono-(9-anthrylmethylphosphonate) bisteroid was studied, which enabled modelling of the ordering potential of the donor. Values of the two-photon absorption tensor components were obtained. To describe the discrepancy between the measured values of the initial anisotropy and fundamental anisotropy predicted by theory the distribution of absorption tensor caused by fast processes have been introduced. An angular parameter of absorption tensor was determined. Reasonable values of the distance between the 9-anthrylmethyl groups, as well as for their mutual orientation were obtained.

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  • 2.
    Opanasyuk, Oleg
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johansson, Lennart B-Å
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Extended Förster theory: a quantitative approach to the determination of inter-chromophore distances in biomacromolecules2010In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 12, no 28, p. 7758-7767Article in journal (Refereed)
    Abstract [en]

    This review highlights recent theoretical and experimental advances in the study of biomacromolecular structure by using electronic transfer. The considered electronic transport in the extended Förster theory occurs within donor–acceptor pairs, donor–donor pairs, as well as within regular arrangements of many donors which may undergo reorienting and translational dynamics. The classical and the extended FoЁ rster theory are compared. Applications concern the determination of structural properties of proteins and non-covalent protein polymers. Studies of energy migration by means of two-photon excited fluorescence spectroscopy, as well as the relevant extension of the Förster theory are presented.

  • 3.
    Opanasyuk, Oleg
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Johansson, Lennart B-Å
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    On the analyses of fluorescence depolarisation data in the presence of electronic energy migration: Part I. Theory and general description2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, p. 1907-1916Article in journal (Refereed)
    Abstract [en]

    A new and general procedure is described for a detailed analysis of time-resolved fluorescence depolarisation data in the presence of electronic energy migration. An isotropic ensemble of bifluorophoric molecules (D1-R-D2) has been studied to demonstrate its utility. Intramolecular donor-donor energy migration occurs between the two donor groups (D), which are covalently connected to a rigid linker group (R). These groups undergo restricted reorientational motions with respect to the R group. The analysis of depolarisation data basically involves the search for best-fit parameters which describe the local reorienting motions, the intermolecular D1-D2 distance, as well as the mutual orientations of the donors. For this, the analysis is partly performed in the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process has been described by using Monte Carlo simulations and an extended Förster theory (EFT). It is found that the EFT provides the least time-consuming computational method. Since one-photon and two-photon excited fluorescence experiments can be applied for energy migration studies, a general and unified theoretical formulation is given.

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  • 4.
    Opanasyuk, Oleg
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mikaelsson, Therese
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ryderfors, Linus
    Department of Photochemistry and Molecular Science, Uppsala University, P. O. Box 523, S-751 20 Uppsala, Sweden.
    Mukhtar, Emad
    Department of Photochemistry and Molecular Science, Uppsala University, P. O. Box 523, S-751 20 Uppsala, Sweden.
    Johansson, Lennart B-Å
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    On the analyses of fluorescence depolarisation data in the presence of electronic energy migration.: II. Applying & Evaluating Two-Photon Excited Fluorescence2012In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 14, p. 1917-1922Article in journal (Refereed)
    Abstract [en]

    Electronic energy migration within a bifluorophoric molecule has been studied by time-resolved two-photon excited (TPE) fluorescence depolarisation experiments. Data were analysed by using a recently developed quantitative approach [Opanasyuk, O. & Johansson, L. B.-Å., On the Analyses of Fluorescence Depolarisation Data in the Presence of Electronic Energy Migration. I. Theory & General Description. Phys. Chem. Chem. Phys., Submitted.]. The energy migration occurs between the 9-anthrylmethyl groups of the bifluorophoric molecule, bis-(9-anthrylmethylphosphonate) bisteroid. These groups undergo local reorientations, while overall tumbling of the bisteroid is strongly hampered in the used viscous solvent, 1,2-propanediol. To solely obtain information about local reorientations of the 9-anthrylmethyl group, also the mono-(9-anthrylmethylphosphonate) bisteroid was studied, which enabled modelling of the ordering potential shape. The analysis of data is partly performed in the Fourier domain and the best-fit parameters are determined by using an approach based on a Genetic Algorithm. The energy migration process was described by an extended Förster theory (EFT). A reasonable value of the distance between the 9-anthrylmethyl groups is found, as well as for the mutual orientation of the ordering potentials. Furthermore, values of the two-photon tensor components were obtained.

  • 5.
    Opanasyuk, Oleg
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Ryderfors, Linus
    Department of Photochemistry and Molecular Science, Uppsala University, P. O. Box 523, S-751 20 Uppsala, Sweden.
    Mukhtar, Emad
    Department of Photochemistry and Molecular Science, Uppsala University, P. O. Box 523, S-751 20 Uppsala, Sweden.
    Johansson, Lennart B-Å
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Two-photon excited fluorescence depolarisation and electronic energy migration within donor–donor pairs2009In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, no 11, p. 7152-7160Article in journal (Refereed)
    Abstract [en]

    A unified theoretical description is presented for one- and two-photon excited fluorescence depolarisation and electronic energy migration within pairs of chromophores. Two weakly coupled donor groups are linked via a rigid macromolecule with the ability to undergo restricted reorienting motions. Describing these reorienting motions as well as their influence on the coupling is rather complex, but can be accounted for by using the extended Förster theory. Here explicit expressions have been derived for chromophores belonging to the point groups D2h,D2 andC2v when residing in uniaxial potentials (i.e. C∞v symmetry). From the given basic equations, it is possible however, to derive the relevant equations for molecules of arbitrary symmetry in any uniaxial orienting potential. The expected time-resolved fluorescence anisotropy for different two-photon absorption tensors are compared for reorienting fluorophores in liquids, as well as in anisotropic systems. Simulated fluorescence depolarisation data are also displayed that mimic energy migration within pairs of two-photon excited donor molecules, which simultaneously undergo reorienting motions within effectively isotropic and uniaxially anisotropic environments. The obtained results demonstrate that the time-resolved fluorescence anisotropy strongly depends on the properties of the two-photon absorption tensor, as well as on using a linear or a circular polarisation of the excitation field.

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