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TOLUIDINE BLUE: THE MODE OF PHOTODYNAMIC ACTION IN YEAST CELLS
Author(s) -
Ito Takashi
Publication year - 1977
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.1751-1097.1977.tb07423.x
Subject(s) - acridine orange , toluidine , singlet oxygen , acridine , in vivo , chemistry , methylene blue , yeast , photochemistry , photosensitizer , in vitro , biophysics , microbiology and biotechnology , biochemistry , oxygen , biology , apoptosis , photocatalysis , genetics , organic chemistry , catalysis
— Toluidine blue, a thiazine dye, was shown to have in vivo photodynamic activity through singlet oxygen (O 2 1 Δ g ) production. This was based mainly on the effective protection by N ‐ 3 and the marked enhancement in D 2 O for the sensitized inactivation of yeast cells. The mode of the in vivo activity was, however, quite different from that of acridine orange, for which the singlet oxygen mechanism has also been proposed. The most characteristic feature in the toluidine blue‐sensitization was the total lack of the induction of gene conversion (at trp 5), while the survival went down below 10%. The non‐induction of genetic changes was confirmed at several pH's in the neutral region, whereas the inactivation was seen in parallel to the reported pH dependence of singlet oxygen production in vitro . Direct measurements by microspectrophotometry showed none of the toluidine blue was accumulated in the cell. It was also ascertained from acridine‐sensitized induction of gene conversion that toluidine blue never interfered with the binding of acridine orange to cellular DNA. These findings suggested that the unique mode of photodynamic activity of toluidine blue is attributable to its action from outside of the cell. Furthermore, comparisons between the photodynamically treated cells (with toluidine blue) and non‐treated cells with respect to the response to UV irradiation excluded certain cell functions relating to the expression of gene conversion from the possible damage sites. The photo‐reactivation process of UV induced gene conversion was not disturbed by the pre‐toluidine blue sensitition. In view of the foregoing results, the plasma membrane was tentatively suggested as the most likely site of damage.