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Subcellular Distributions and Excited‐State Processes of Hypericin in Neurons
Author(s) -
English Doug. S.,
Doyle Robert T.,
Petrich Jacob W.,
Haydon Philip G.
Publication year - 1999
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1999.tb03290.x
Subject(s) - hypericin , excited state , fluorescence , biophysics , chemistry , photochemistry , atomic physics , physics , optics , biology , pharmacology
— The photodynamic drug, hypericin, is studied in fetal rat neurons using fluorescence microscopy. Hypericin has an extremely high affinity for the cell membrane and is found to a smaller extent in the nucleus. Fluorescent excitation of hypericin is shown to cause irreversible damage to the cell membranes of living neurons. Fixed cells were used to make ultrafast time‐resolved measurements to avoid the deleterious effects of long‐term exposure to intense light and room temperatures. To our knowledge, these are the first ultrafast time‐resolved measurements of the fluorescence lifetime of hypericin in a subcellular environment. Nonexponential fluorescence decay is observed in hypericin in the neurons. This nonexponential decay is discussed in terms of other examples where non‐exponential decay is induced in hypericin upon its binding to biomolecules. The nonaradiative processes giving rise to the nonexponential hypericin decay are attributed to excited‐state electron transfer, excited‐state proton transfer or both.