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Fluorescence Anisotropy Imaging Reveals Localization of meso-Tetrahydroxyphenyl Chlorin in the Nuclear Envelope

Authors

  • Thomas H. Foster,

    Corresponding author
    1. Department of Imaging Sciences, University of Rochester, Rochester, NY
    2. Department of Physics and Astronomy, University of Rochester, Rochester, NY
    3. Institute of Optics, University of Rochester, Rochester, NY
      *To whom correspondence should be addressed: Department of Imaging Sciences, University of Rochester, 601 Elmwood Avenue, Box 648, Rochester, NY 14642, USA. Fax: 585-273-1033; e-mail: thomas.foster@rochester.edu
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  • Benjamin D. Pearson,

    1. Department of Physics and Astronomy, University of Rochester, Rochester, NY
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  • Soumya Mitra,

    1. Department of Imaging Sciences, University of Rochester, Rochester, NY
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  • Chad E. Bigelow

    1. Institute of Optics, University of Rochester, Rochester, NY
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    • †Current address: Physical Sciences, Inc., 20 New England Business Center, Andover, MA 01810, USA.


*To whom correspondence should be addressed: Department of Imaging Sciences, University of Rochester, 601 Elmwood Avenue, Box 648, Rochester, NY 14642, USA. Fax: 585-273-1033; e-mail: thomas.foster@rochester.edu

ABSTRACT

We have measured the intrinsic fluorescence anisotropies of six photosensitizers in homogeneous solution, and we have imaged the anisotropies of these sensitizers in tumor cell monolayers using polarization-sensitive laser-scanning confocal microscopy. The intrinsic anisotropies are unremarkable and are within the approximate range of 0.2–0.27. In cells, however, very interesting behavior is exhibited by meso-tetrahydroxyphenyl chlorin (mTHPC). Polarization-sensitive images of mTHPC's fluorescence show a pronounced banding of alternating high and low anisotropy consistent with an ordering of the sensitizer in the nuclear envelope, indicating that this structure is a target of photodynamic damage with this sensitizer. None of the other sensitizers exhibits localization to the nuclear envelope. The frequency distributions of the intracellular anisotropies of the sensitizers exhibit variable peaks and widths. An unusual case is that of Photofrin, with a peak in its anisotropy frequency distribution of –0.12. The change from a positive intrinsic anisotropy in homogeneous solution to a negative value in cells suggests an environmentally induced change in the relative orientations of the absorption and emission dipole moments.

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