Primary Processes of Photosynthesis

Barber, J., Topics in Photosynthesis, Vol. 2 Primary Processes of Photosynthesis, Elsevier, Amsterdam, 1977. 

Bolton, J.R. "Primary Processes of Photosynthesis" (Barber, J., ed.) Elsevier/North Holland Biomedical Press Amsterdam, 1977 pp 188-201. 

The highly oriented molecules in thin organic films such as Langmuir-Blodgett (LB) films and self-assembled monolayers (SAM) [1] are essential for some molecular functions. Non linear optical and opto-electronic properties are two of the most important and interesting functions of these molecular assemblies. In the past more than thirteen years, simulation of the primary process of photosynthesis using such molecular assemblies and its application to molecular photodiodes [2,3] have been one of the main subjects of our laboratory. 

In an early review2 A. J. Hoff called the primary processes of photosynthesis a Garden of Eden for EPR spectroscopists . And indeed this techniques plays until today a major role in this field of research and the results derived from EPR and related experiments have contributed very substantially to our knowledge about the details of the light-induced processes and of the coupled enzymatic reactions. 

The triplet-triplet quenching mechanism implying as it does, the concentration of the energy from two separately absorbed quanta on a single molecular species, should also be considered as a possible participant in the primary processes of photosynthesis, where just such a concentration of quanta is necessary to provide the energy required for the photochemical reactions. 

The initial or primary processes of photosynthesis occur in the reaction centers in which chlorophyll or bacteriochlorophyll absorbs a photon.3183 Then, the chlorophyll, in its singlet excited state (Chi ), donates an electron to some acceptor A to form a radical A-and to leave an oxidized chlorophyll Chl+ radical (Eq. 23-31). 

The primary process of photosynthesis (in both photosystems) is an electron transfer reaction from the electronically excited chlorophyll molecule to an electron acceptor, which is in most cases a quinone. This primary electron acceptor can then hand over its extra electron to other, lower energy, acceptors in electron transport chains which can be used to build up other molecules needed by the organism (in particular adenosine triphosphate ATP). The complete process of photosynthesis is therefore much... 

Our work in this area is on the primary processes of photosynthesis which occur in the photochemical, i.e. the excited state, regime which, in turn, is confined to the first few nanoseconds of the process. 

Renger G. Primary Processes of Photosynthesis - Part 1. Cambridge RSC, 2008. 

Renger G, editor. Primary processes of photosynthesis, part 2. Principles and apparatus. Cambridge, UK RSC Publishing 2008. 

Knox R. Photosynthetic efficiency and excitation transfer and trapping in primary processes of photosynthesis. In Topics in Photosynthesis. Barber 1, eds. 1977. Elsevier-North Holland. Amsterdam, pp. 55-97. 

The other new aspect of our work was that it provided the first detailed structure of the photosynthetic reaction center. Thus it helped to understand how light energy is converted into chemical energy in the primary process of photosynthesis. 

The laser supercontinuum source has found numerous applications in the physical, chemical, and biological sciences. Many studies have concerned elementary photochemical and photobiological reactions such as those involved in the primary processes of photosynthesis and vision (von der... 

Chlorophylls.—Aspects of the primary processes of photosynthesis which have recently been reviewed include excitation energy transfer in photosynthesis,376 primary photochemical reactions in chloroplast photosynthesis,373 light-induced paramagnetism in photosynthetic systems,377 and photosynthetic reaction centres and primary photochemical reactions.378... 

Energy Transfer and Excitons are, as we have already mentioned, perhaps the most interesting and in any case the most characteristic photophysical processes in molecular crystals. The investigation of these processes began in 1934, when A. Winterstein, U. Schon and H. Vetter [5] were able to explain the green fluorescence radiation from anthracene crystals, which had been described as due to the effect of an unknown chrysogen , in terms of sensitised fluorescence. This fluorescence is emitted by tetracene molecules which are present at very low concentration in the anthracene. Pure anthracene fluoresces in the crystalline phase just as in solution with a blue-violet colour. This observation set off a large number of spectroscopic studies of the sensitised emission from mixed crystals. Very soon, J. Franck and E. Teller [6] pointed out in a summary report of this field that there was an important cormection here to the primary processes of photosynthesis and other biophysical processes. 

New and highly efficient synthetic routes have generated many porphyrinlike compounds with unique characteristics for their uses in several other applications like oxidative catalysis [ 19,20] and as biomimetic model systems of the primary processes of photosynthesis [21,22]. Presently, the interest includes also the supramolecular units, including molecular recognition in chemical receptors and sensors [23-25], use as light-harvesting devices [26-29], and as materials for advanced technologies, mainly in nanosciences [30, 31]. 

The FTIR difference spectra obtained from steady state illumination of preparations containing only or both Qa and Qb surprisingly show no large changes for the transitions PIQ>i —> P+IQ>i and PIQaQb —> P IQaQb One explanation could be that the vibrations arising from Q i" and occur at approximately the same frequencies another possible explanation is that the absorption bands are very small and therefore are masked by stronger absorbance bands. Further studies with isotopically labelled quinones and with amino acid labelled RC s should provide reliable assignments of bands and thereby more detailed information on the molecular events involved in the primary processes of photosynthesis. 

Only a very small part of the plant s C. (molecules of Cm or bacteriochlorophyll a) is directly active in Photosynthesis (see). Active centers consisting of C.a, or Cmjj complexed with Plastoquinone (see) are absolutely necessary for the primary process of photosynthesis. More than 99% of the C. serve as accessory pigments, as do the thylakoid Carotenoids (see) whidi trap and funnel light to the active centers of Photosystems I and II (see). Fig. 2 shows the possibilities for conversion of electronic energy resulting from the trapping of a photon by a C. molecule. 

Seely GR (1977) In Barber J (ed) Primary Processes of Photosynthesis Elsevier, Amsterdam, pp 1-53... 

M. Nishimura, "Primary Processes of Photosynthesis". Kyoritsu Shuppan, Tokyo(1975), Ch. 2. 

In the course of photosynthesis water must be cleaved. All of the processes that are related to the cleavage of water-photolyse, are called the primary processes of photosynthesis. To these belong not only photolysis but also the noncyclic electron transport, which is tightly coupled to it, and cyclic electron transport. 

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