Читать книгу Molecular Mechanisms of Photosynthesis - Robert E. Blankenship - Страница 63

Chlorophyll d is different from chlorophyll a in only one respect: the substituent at the C‐3 position is a formyl group in chlorophyll d, instead of the vinyl group found in chlorophyll a. For many years, chlorophyll d was known only as a trace constituent of certain red algae and was suspected to be an experimental artifact. However, in 1996, a cyanobacterium, Acaryochloris marina, was discovered as a symbiont in a marine animal called an ascidian. This organism contains chlorophyll d as the major pigment, although it also contains small amounts of chlorophyll a. It now appears that chlorophyll d is only found in cyanobacteria, and that earlier reports of chlorophyll d in red algae result from contamination of the algal surface by epiphytic cyanobacteria that contain chlorophyll d (Larkum and Kuhl, 2005). The electron withdrawing formyl group at the C‐3 position adjacent to the y molecular axis of the pigment has the effect of shifting the absorption maximum of chlorophyll d to longer wavelengths compared to chlorophyll a. It has therefore received attention as a possible pigment to expand the solar spectrum in bioenergy applications (Chen and Blankenship, 2011).