Photosynthesis, artificial antenna function

As indicated in Figure I, wild-type bacterial reaction centers also contain a carotenoid polyene. This polyene is not involved as a donor or acceptor in the normal electron transfer sequence, although carotenoid radical cations have been observed spectroscopically in photosynthetic preparations under certain conditions [18,19]. In many of the artificial photosynthetic systems which will be discussed below, the carotenoid is used as a convenient secondary electron donor. Carotenoids do perform two important functions in photosynthesis. They provide photoprotection from singlet oxygen damage, and act as light-gathering antennas for the special pair (see Sections III and IV). 

---