Porphyrin inactivated catalase through the production of singlet oxygen
, which caused amino acid damage (Hirakawa et al.
Boxin Ou's group at International Chemistry Testing (Milford, MA), using the ROS, superoxide anion, hydroxyl radical and singlet oxygen
, and the RNS per-oxynitrite and the RCS hypochlorite.
Hydroxyanthraquinones as sensitizers of singlet oxygen
reactions: quantum yields of triplet formation and singlet oxygen
generation in acetonitrile.
The photosensitizers, when irradiated, are probably attacked by the singlet oxygen
They are organized into sections devoted to the structural properties, characteristics, and interactions of carotenoids; analytical methodologies for the measurement of carotenoids; application of spectroscopic methodologies to carotenoid systems; chemical breakdown of carotenoids in vitro and in vivo; antioxidant and photoprotection functions and reactions involving singlet oxygen
and reactive oxygen species; cell culture methods applied to understanding carotenoid recognition and action; the chemistry and biochemistry of carotene oxidases, cell regulation, and cancer; and carotenoids and carotenoid biochemistry in animal systems.
3-10) PDT causes the photochemical generation of cytotoxic reactive oxygen species such as singlet oxygen
within the target tissue.
When the photosensitizer is exposed to light its molecules will be excited and by decaying through the triplet state there will be a generation of singlet oxygen
(1O2) and reactive oxygen species (ROS) which are toxic to cells and tissue (Ding, et al.
Too much radiation can actually be counterproductive: "At high doses an excessive amount of singlet oxygen
can be produced, and its chemical action can be detrimental to cells," Smith explains.
A] is reduced, but this is followed by a rapid charge recombination that may lead to the generation of harmful singlet oxygen
species; see accompanying Box on singlet oxygen
production in PSII.
The images reveal the physical changes that occur inside cancer cells at the time when they are dying because of Photodynamic Therapy (PDT)-a cancer treatment that uses light to activate a drug that creates a short-lived toxic type of oxygen, called singlet oxygen
, which kills cancerous cells.
For example singlet oxygen
can be produced by a reaction between the dissolved triplet oxygen and the excited triplet state of erythrosine B.
It has been theorized that zeaxanthin and lutein are concentrated in the retina because of their ability to quench singlet oxygen
and to scavenge free radicals--because they pass through the blood and eye brain barriers and are required in the oxygen-rich environment of the retina to prevent light-mediated free radical damage to the retina.