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Abstract
Reactive oxygen species comprise oxygen-based free radicals and non-radical species such as peroxynitrite and electronically excited (singlet) oxygen. These reactive species often have short lifetimes, and much of our understanding of their formation and reactivity in biological and especially medical environments has come from complimentary fast reaction methods involving pulsed lasers and high-energy radiation techniques. These and related methods, such as EPR, are discussed with particular reference to singlet oxygen, hydroxy radicals, the superoxide radical anion, and their roles in medical aspects, such as cancer, vision and skin disorders, and especially pro- and anti-oxidative processes.
Highlights
Introduction of Their Roles inBiology and Medicine.Reactive oxygen species (ROS) are involved in many biological and medical processes, ranging from photosynthesis to skin photosensitivity, vision, cancer, and sometimes areas of major commercial interest, such as skin protection and the preservation of items of historical importance
Lut that the equilibrium is more the left than on forthe theformation other of peroxyl radicals: carotenoids. These results suggest that Lut is a significantly better protector of the
We speculate there may be a link between the increased photo-induced radicals in fair-skinned individuals compared to dark-skinned, leading to higher severity of COVID-19 in the dark-skinned BAME community, with partial protection for fair-skinned individuals arising from ROS, generated from both the photolysis of PM and its photoinduced rearrangement
Summary
The major interest is 1 O2 generated via an energy transfer from an (excited) triplet state. Pulsed laser studies in non-polar solvents lead to high yields of triplet states and 1 O2 from all the retinal isomers. The environment (solvent dependence) is important with the triplet yields being much lower in polar solvents than in non-polar solvents. A state of 1 π-π* character is located below 3 n-π* and is the lowest excited singlet state. In non-polar, non-H-bonding solvents, a 1 n-π* state which has a higher energy level than the 3 π-π* is the lowest excited singlet state, meaning that a high yield of 1 O2 is generated, leading to significant photo-oxidative damage. The 1 O2 yield is much lower in polar solvents [17]; for example, in methyl alcohol, it is 0.08 for all-trans-retinal, whereas it is in the range of 0.2–0.5 in non-polar solvents [11]
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