Joint Study on the Photodynamictherapy by Chlorophylls

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Plasmid DNA has been efficiently photocleaved under anaerobic condition by water soluble phephorbides (sodium pheophorbides ; Na-Phdes) a, b and a novel coproporphyrin III with zinc (Zincphyrin) produced by Streptomyces sp. Singlet oxygen production sensitized by Na-Phdes a or b can not be observed in the aqueous media, although Zincphyrin produced singlet oxygen in ca. 17% quantum yield. Direct evidence for the electron capture from nucleic acid bases, adenine and guanine, by porphyrin-derivatives in the singlet excited states has been first obtained, by using nucleobase-attached porphyrins. A guanine-attached porphyrin showed strongest reduction of fluorescence derived from porphyrin ring, and an adenine-attached one showed secondaly strongest reduction. This is the first evidence in support the electron transfer mechanism for the exygen-independent photocleavage of DNA.Fluorescence microscopic observation has shown a rapid incorporation of Na-Phde a and Zincphyrin into nuclei, mitochondria and lysosome of human oral mucosa cells, although Na-Phde b has been incorporated only into the plasma membrane. Red fluorescence from Na-Phde a and zincphyrin has rapidly decayd durint the microscopic observation, indicating that some photochemical reactions take place in the organelle.