Effect of the photocatalytic activity of TiO(2) on plasmid DNA.
We investigated the photodynamic DNA strand-breaking activity of TiO(2). A solution of super-coiled pBR 322 DNA was irradiated with 5 J/cm(2) of UVA in the presence of TiO(2) and the products were analyzed by using gel electrophoresis. The ratio of open-circular DNA to super-coiled circular DNA was calculated from the resulting peak areas as a DNA strand-breaking index (SBI). The SBI of anatase-structure TiO(2) (band gap=3.23 eV) was greater than that of rutile structure (band gap=3.06 eV), and the level of SBI correlated with the photocatalytic activity for degradation of 2-propanol. The inhibitory effects of active oxygen scavengers, including DMSO, glutathione and histidine, on the DNA strand-breaking activity were examined. All of the scavengers except ascorbic acid showed inhibitory effects, as did several polyhydric alcohols including mannitol, a well-known hydroxyl radical scavenger. These results suggest that the photodynamic DNA strand-breaking activity of TiO(2) is due to active oxygen species, especially hydroxyl radicals. Polyhydric alcohols showed an inverse correlation between the inhibitory effect on DNA strand-breaking activity and the octanol/water partition coefficient (logP).
Ashikaga
T
T
Life Science Research Center, Safety Research Labs, Shiseido, 1050, Nippa-cho, Kohoku-ku, Yokohama, Japan. takao.ashikaga@to.shiseido.co.jp
Wada
M
M
Kobayashi
H
H
Mori
M
M
Katsumura
Y
Y
Fukui
H
H
Kato
S
S
Yamaguchi
M
M
Takamatsu
T
T
D001205:Ascorbic Acid / Q000494:pharmacology; D004247:DNA / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage / Q000187:drug effects; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D006639:Histidine / Q000494:pharmacology; D008353:Mannitol / Q000494:pharmacology; D017319:Photosensitizing Agents / Q000494:pharmacology*; D010957:Plasmids / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects; D013402:Sugar Alcohols / Q000494:pharmacology; D014025:Titanium / Q000494:pharmacology*; D014466:Ultraviolet Rays
D016166:Free Radical Scavengers; D017319:Photosensitizing Agents; D013402:Sugar Alcohols; C009495:titanium dioxide; D008353:Mannitol; D006639:Histidine; D004247:DNA; D014025:Titanium; D005978:Glutathione; D001205:Ascorbic Acid; D004121:Dimethyl Sulfoxide