ABSTRACT
Biliproteins and other antenna pigments were therefore shown to be essential parts of the efficient operation of the photosynthetic apparatus. The action spectrum for photosynthesis of a cryptomonad alga has been measured by Haxo and Fork. Phycobilisomes are composed of a variety of biliproteins in which excitation energy migrates from the short-wavelength absorbers, phycoerythrin or phycoerythrocyanin when present, to phycocyanin to allophycocyanin to the two types of allophycocyanin 680. From the two types of allophycocyanin 680 the excitation energy is both energetically favorable and at the closest proximity for transfer, probably via Forster very weak coupling of dipoles, to chlorophyll a in the thylakoid membrane. The small fraction of chlorophyll a in photosystem II acted as a conduit for funneling excitation energy from the phycobilisomes to the photosystem II reaction centers or for spillover to photosystem I. Confirmation of a structural nature for these assignments came from studies on isolated chlorophyll-protein complexes.
