Photoprotective mechanism

In addition, Montenegro et al., (2007) determined that the photosensitized RF-mediated degradation of vitamins A, D3, and RF itself in skimmed milk was strongly reduced by the addition of small amounts of lycopene-gum arabic-sucrose microcapsules, prepared by spray-drying. Under these conditions, the bulk properties of the skimmed milk were unmodified. The main photoprotection mechanism of the milk vitamins was the efficient quenching of the 3Rf by the protein moiety of GA. Small contributions (<5%) to the total photoprotection percentage was due to both inner filter effect and 1O2 quenching by the microencapsulated lycopene. 

Bailey, S., N. Mann, C. Robinson, and D. J. Scanlan (2005). The occurrence of rapidly reversible non-photochemical quenching of chlorophyll a fluorescence in cyanobacteria. FEBS Lett 579(1) 275-280. Boulay, C., L. Abasova, C. Six, I. Vass, and D. Kirilovsky (2008a). Occurrence and function of the orange carotenoid protein in photoprotective mechanisms in various cyanobacteria. Biochim Biophys Acta 1777(10) 1344-1354. 

The fourth section focuses on individual and sub-individual effects and responses. The first chapter within this section (Chapter 9) reviews the effects of UVR on DNA, which has long been identified as one of the primary targets of UVR in biological systems. It is followed by a discussion of the main physiological photoprotective mechanisms in aquatic organisms (Chapter 10), Chapter 11 reviews the available literature on UVR effects on autotrophs, while Chapters 12 and 13 present two different and complementary perspectives on the effects of UVR on heterotrophs. This section ends with an extensive review on the role of sensory systems and behavioral responses to UVR (Chapter 14). 

As described in other chapters, carotenoid radicals may also occur in photosynthetic systems and take part in some of the photoprotective mechanisms, or may participate as integral parts in the light-induced charge separation in artificial electron transfer chains. 

It is apparent that whilst isolated chloroplasts and thylakoids of C. fragile are most susceptible to photoinhibition and photooxidative damage, intact fronds are surprisingly tolerant. Photoprotective mechanisms must therefore exist in situ that are absent in organello. We believe that the answer involves the arrangement of the chloroplasts within the algal frond. 

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