Photosystem light damage

Eosin generates singlet oxygen upon irradiation with visible light. Its ability to act as a photodynamic sensitizer has been known for many years [125], Irradiation of Eosin in the presence of oxygen is found to deactivate viruses [126] and yeasts [127] and to damage the photosystem II of leaf tissue [128,129], Eosin covalently immobilized in polystyrene beads has been used to remove E. coli from drinking water [130],... 

See also Pyrimidine Dimers, O -Alkylguanine Alkytransferase, Types and Consequences of DNA Damage, Light Absorbing Pigments (from Chapter 17), Photochemistry (from Chapter 17), Photosystem Summary (from Chapter 17)... 

During winter, high light and freezing temperatures interact to cause damage to photosynthesis of pine (1). The photochemicai efficiency of photosystem II (PS II), the quantum yield and the rate of light saturated photosynthesis are severely inhibited during natural winter conditions. Strand and Oquist (2, 3) have shown that winter stress of Scots pine involve both photoinhibition of photosystem II and frost inhibition of the enzymes in the Calvin cycle or the photophosphorylation. In the field it may take several months before full photosynthetic efficiency is restored after the winter (4, 5). 

Photosystem II reaction center is susceptible to light induced damage and steady state photosynthesis is maintained by continual repair of the photo-inactivated photosystems. An increase in the rate of inactivation (by over excitation of PS II) or a decrease in the rate of repair of PSII centers can result in accumulation of damaged PS II and consequent photoinhibition of photosynthesis. Since the assembly and stability of PS II complex involves close interaction with membrane lipids, photoinhibition and recovery of PS II centers are likely to be affected by the lipid composition of the thylakoid membrane. 

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