Carotenoids light-harvesting role

Finally, carotenoids are the metabolic precursors for three more of the flavor volatiles of the tomato. Although the role of carotenoids, light-harvesting pigments in plants, in human nutrition is the subject of debate, these compounds are antioxidants and P-carotene is the principal source of the visual pigments of the eye. 

In this chapter we shall summarize the structure of the LH2 (B800-850) antenna complex from the purple non-sulfur photosynthetic bacterium Rhodopseudomonas acidophila strain 10050, placing special emphasis on the carotenoids. We will then review what is currently known about the details of the carotenoid s light-harvesting role in this system. 

Although all chlorophyll-protein complexes isolated to date, whether they are associated with PS I or II, contain carotenoids, it is only in two classes of complexes that carotenoids play the major light-harvesting role. These two classes are the unique... 

Koyama, Y., F. S. Rondonuwu, R. Fujii, and Y. Watanabe. 2004. Light-harvesting function of carotenoids in photosynthesis The roles of the newly found 1B state. Biopolymers 74 2-18. 

Carotenoids exhibit multiple physiological roles, i.e. as light-harvesting pigments in photosynthesis, as quenching solutes for the triplet state of chlorophyll a to... 

Fig. 1 (B) illustrates the second major function of carotenoids, namely, photoprotection of chlorophyll, either by direct triplet-triplet energy transfer [labeled T-T j from Chl to the carotenoid or by indirect transfer via the formation of singlet oxygen. The reaction steps for each of the two mechanisms are shown in Fig. 1, bottom, right. Further details on both the light harvesting by carotenoids and photoprotective role of carotenoids will be described in the following sections.

Fig. I. Structures of some carotenoids known to play a major role in light-harvesting in eukaryotic algae a) peridinin b) fuco-xanthin c) siphonaxanthin d) prasinoxanthin.

I. Introduction Possible Structural Role of Carotenoids in the Assembly of Light-harvesting Complexes... 124... 

---