| 15950386 |
Tsuchiya K, Akai K, Tokumura A, Abe S, Tamaki T, Takiguchi Y, Fukuzawa K: Oxygen radicals photo-induced by ferric nitrilotriacetate complex. . Biochim Biophys Acta. 2005 Aug 30;1725(1):111-9.
This study examined the photo-induced generation of reactive oxygen species (ROS) by the carcinogenic iron (III)-NTA complex. Iron (III)-NTA complex (1:1) has three conformations (type (a) in acidic conditions of pH 1-6, type (n) in neutral conditions of pH 3-9, and type (b) in basic conditions of pH 7-10) with two pK (a) values (pK (a1) approximately 4, pK (a2) approximately 8). The iron (III)-NTA complex was reduced to iron (II) under cool-white fluorescent light without the presence of any reducing agent, and the reduction rates of the three conformations of iron (III)-NTA were in the order type (a)> type (n)> type (b) as reported previously (Akai K. et al., Free Radic. Res. 38, 951-962, 2004). ROS generation was investigated by electron paramagnetic resonance (EPR) spectroscopy with a spin-trapping technique. Apparent EPR signals attributed to PBN/*(13) CH (3) and PBN/*OCH (3) spin adducts were observed after incubation of the iron (III)-NTA complex was mixed with alpha-phenyl-tert-butylnitrone (PBN) and (13) C-DMSO in an aerobic condition. The addition of catalase effectively attenuated the PBN adducts, but superoxide dismutase enhanced them. Taken together, these results indicate that the iron (III)-NTA complex is spontaneously reduced to the iron (II)-NTA complex by light under acidic to neutral pH, and in turn transfers an electron to molecular oxygen to form ROS. |
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