Phytochrome, the photomorphogenetic reaction center pigment of green plants and some algae, has been proposed recently to contain two chemically different chromophores in its P, and P,, forms, respectively (Grombein et al., 1975). P, contains an A-dihydrobilin chromophore (1) closely related to that of phycocyanin. For P,,, a violin (2) (or possibly purpurin) (Scheer et al., 1976) type chromoph...

In the last five year our research group have been starting to explore the unique and extremely different cyanobacteria world, a group of Gram-negative photosynthetic bacteria, able to inhabit any kind of water environment, such as coastal and inland waters. Their name derives from the capacity to produce, during their photosynthetic processes, a blue-green coloured pigment, called c-phycocyani...

The photochemistry of C-phycocyanin has been studied after denaturation in the dark. It shows an irreversible reaction which has characteristics of a Z .Z .E to Z ,Z,Z-isom erization of dihydrobilins. Its amplitude depends on the reaction conditions, with a maximum corresponding to 15% conversion of one of the three PC chromophores. This chromophore is suggested to be ß-153, for which recent X-...

Transport processes and spectroscopic phenomena in light harvesting proteins depend sensitively on the characteristics of electron-phonon couplings. Decoherence imposed by low-frequency nuclear motion generally suppresses the delocalization of electronic states, whereas the Franck-Condon progressions of high-frequency intramolecular modes underpin a hierarchy of vibronic Coulombic interactions ...

Multicellular marine plants were collected from their natural habitats and the quantum efficiency of their photosynthesis was determined in the laboratory in five narrow wave length bands in the visible spectrum. The results along with estimates of the relative absorption by the various plastid pigments show a fairly uniform efficiency of 0.08 molecules O(2) per absorbed quantum for (a) chlorop...

Phycobilisomes, the light-harvesting complexes of cyanobacteria and red algae, contain two to four types of chromophores that are attached covalently to seven or more members of a family of homologous proteins, each carrying one to four binding sites. Chromophore binding to apoproteins is catalyzed by lyases, of which only few have been characterized in detail. The situation is complicated by n...

Occurrence and toxicity of Microcystis spp. were measured by ELISA in three impoundments of the Huron River in southeast Michigan, USA. Assays were conducted weekly from June through October 2005. Additional samples were collected to assess microcystin concentrations throughout the drinking water treatment process at the Ann Arbor Water Treatment Facility. Water column stability, nutrient conce...