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- Björn, Lars Olof, et al.
(author)
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A viewpoint: Why chlorophyll a?
- 2009
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In: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 99:2, s. 85-98
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Research review (peer-reviewed)abstract
- Chlorophyll a (Chl a) serves a dual role in oxygenic photosynthesis: in light harvesting as well as in converting energy of absorbed photons to chemical energy. No other Chl is as omnipresent in oxygenic photosynthesis as is Chl a, and this is particularly true if we include Chl a2, (=[8-vinyl]-Chl a), which occurs in Prochlorococcus, as a type of Chl a. One exception to this near universal pattern is Chl d, which is found in some cyanobacteria that live in filtered light that is enriched in wavelengths [700 nm. They trap the long wavelength electronic excitation, and convert it into chemical energy. In this Viewpoint, we have traced the possible reasons for the near ubiquity of Chl a for its use in the primary photochemistry of Photosystem II (PS II) that leads to water oxidation and of Photosystem I (PS I) that leads to ferredoxin reduction. Chl a appears to be unique and irreplaceable, particularly if global scale oxygenic photosynthesis is considered. Its uniqueness is determined by its physicochemical properties, but there is more. Other contributing factors include specially tailored protein environments, and functional compatibility with neighboring electron transporting cofactors. Thus, the same molecule, Chl a in vivo, is capable of generating a radical cation at ?1 V or higher (in PS II), a radical anion at -1 V or lower (in PS I), or of being completely redox silent (in antenna holochromes).
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| 3. |
- Björn, Lars Olof, et al.
(author)
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The evolution of photosynthesis and its environmental impact
- 2008
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In: Photobiology — The science of life and light, 2nd. ed.. - New York, NY : Springer New York. - 9780387726540 ; , s. 255-287
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Book chapter (other academic/artistic)abstract
- Photosynthesis in plants is a very complicated process, utilizing two photosystems in series to carry out the very energy-demanding process of oxidizing water to molecular oxygen and reducing carbon dioxide to organic compounds. The first photosynthetic organisms, living more than 3.4, perhaps even 3.8 Ga, i.e. American billion (109) years ago, carried out a simpler process, without oxygen production and with only one photosystem. A great variety of such one-photosystem photosynthesizers are living even today, and by comparing them, and from chemical fossils, researchers are trying to piece together a picture of the course of the earliest evolution of photosynthesis. Chlorophyll a probably preceded bacteriochlorophyll a as a main pigment for conversion of light into life energy. The process of carbon dioxide assimilation, today taking place mainly in conjunction with photosynthesis, is even older than photosynthesis itself. Oxygenic photosynthesis, i.e. photosynthetic production of molecular oxygen, first appeared in ancestors of present-day cyanobacteria more than 2.7, perhaps already 3.7 Ga ago. Cyanobacteria entered into close association with other organisms more than 1.2 Ga ago, and chloroplasts in green algae and green plants as well as those in algae on the "red" line of evolution (red algae, cryptophytes, diatoms, brown algae, yellow-green algae and others) stem from a single early event of endosymbiotic uptake of a cyanobacterium into a heterotrophic organism. Only ecologically unimportant exceptions from this rule have been found. The chloroplasts on the "red line", excepting those of red algae, stem from a single event of secondary endosymbiosis, in which a red alga was taken up into another organism. There are also examples of tertiary (third level) endosymbiotic events. Thylakoids in land plants are partially appressed and forming grana, while those of, e.g., red algae do not have this structure, and this difference can be explained by the different spectra of ambient light. At the end of the chapter a brief review is given of the evolution of the assimilation of carbon dioxide, the adaptation to terrestrial life, and the impact of photosynthesis on the terrestrial environment.
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- Govindjee, [unknown], et al.
(author)
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Celebrating the millennium: historical highlights of photosynthesis research, part 3
- 2004
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In: Photosynthesis Research. - 0166-8595. ; 80:1-3, s. 1-13
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Journal article (peer-reviewed)abstract
- This paper introduces the third and final part of the 'millennium celebrations of historical highlights of photosynthesis research.' Part 1 ( 308 pages) was published in October 2002 as Vol. 73 of the journal Photosynthesis Research, and Part 2 ( 458 pages) was published in July 2003 as Vol. 76. Here, we recognize particularly the work of three major contributors to our understanding of photosynthesis: Roger Stanier (1916-1982); Germaine Cohen-Bazire (Stanier) (1920-2001); and William Arnold (1904-2001). We also introduce the historical papers contained in this volume; consider the legacy of Alfred Nobel (1833-1896); and identify Nobel prizes of special relevance to understanding the capture, conversion, and storage of light energy in both anoxygenic and oxygenic photosynthesis.
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