Biological photosynthetic reaction

In this chapter results of the picosecond laser photolysis and transient spectral studies on the photoinduced electron transfer between tryptophan or tyrosine and flavins and the relaxation of the produced ion pair state in some flavoproteins are discussed. Moreover, the dynamics of quenching of tryptophan fluorescence in proteins is discussed on the basis of the equations derived by the present authors talcing into account the internal rotation of excited tryptophan which is undergoing the charge transfer interaction with a nearby quencher or energy transfer to an acceptor in proteins. The results of such studies could also help to understand primary processes of the biological photosynthetic reactions and photoreceptors, since both the photoinduced electron transfer and energy transfer phenomena between chromophores of proteins play essential roles in these systems. 

The biological functions of chloroplast ferredoxins are to mediate electron transport in the photosynthetic reaction. These ferredoxins receive electrons from light-excited chlorophyll, and reduce NADP in the presence of ferredoxin-NADPH reductase (23). Another function of chloroplast ferredoxins is the formation oT" ATP in oxygen-evolving noncyclic photophosphorylation (24). With respect to the photoreduction of NADP, it is known that microbial ferredoxins from C. pasteurianum (16) are capable of replacing the spinach ferredoxin, indicating the functional similarities of ferredoxins from completely different sources. The functions of chloroplast ferredoxins in photosynthesis and the properties of these ferredoxin proteins have been reviewed in detail by Orme-Johnson (2), Buchanan and Arnon (3), Bishop (25), and Yocum et al. ( ). 

Biological systems Ligand-myoglobin Protein dynamics Bacteriorhodopsin Light harvesting Pigment-protein complexes Photosynthetic reaction centers... 

The next two chapters are devoted to ultrafast radiationless transitions. In Chapter 5, the generalized linear response theory is used to treat the non-equilibrium dynamics of molecular systems. This method, based on the density matrix method, can also be used to calculate the transient spectroscopic signals that are often monitored experimentally. As an application of the method, the authors present the study of the interfadal photo-induced electron transfer in dye-sensitized solar cell as observed by transient absorption spectroscopy. Chapter 6 uses the density matrix method to discuss important processes that occur in the bacterial photosynthetic reaction center, which has congested electronic structure within 200-1500cm 1 and weak interactions between these electronic states. Therefore, this biological system is an ideal system to examine theoretical models (memory effect, coherence effect, vibrational relaxation, etc.) and techniques (generalized linear response theory, Forster-Dexter theory, Marcus theory, internal conversion theory, etc.) for treating ultrafast radiationless transition phenomena. 

The invention of aerobic photosynthesis, the light-driven oxidation of water to oxygen, stands as one of the pivotal evolutionary innovations in the history of life on Earth. The process is carried out only at the oxygen-evolving complex (OEC) of PSII in plants and algae, as well as in cyanobacteria. Despite the biological uniqueness of water oxidation to 02, several of the core proteins of PSII have homologues in the so-called type I and type II anaerobic photosynthetic reaction... 

Lacshmi, K.V. and Brudvig, G.W. (2000) Electron paramagnetic resonance distance measurement in photosynthetic reaction centers, in Berliner, L, Eaton, S., and Eaton, G. (eds.),, Magnetic Resonance in Biology, V. 18, Kluwer Academic Publishers. Dordrecht, pp. 513-568. 

Takahashi, E., and Wraight, C. A., 1994, Molecular genetic manipulation and characterization of mutant photosynthetic reaction centers from purple non-sulphur bacteria. In Advances in Molecular and Cell Biology Molecular Processes in Photosynthesis, (J. Barber, ed.)... 

Zinth, W., Huppmann, P., Arlt, T., and Wachtveitl, J., 1998, Ultrafast spectroscopy of the electron transfer in photosynthetic reaction centres towards a better understanding of electron transfer in biological systems Phil. Trans. Roy. Soc. Land. A, 356 4659476. 

The formation of a hydrogen bond between the amide proton and one carbonyl oxygen of NQ was indicated in the Ec + —NQ /M" complex to stabilize the complex (see above). Electron-transfer reactions were believed to be regulated through such noncovalent interactions that play an important role in biological ET systems, where electron donors and acceptors are usually bound to proteins at a fixed distance (123-127). Eor example, in the bacterial photosynthetic reaction center (bRC) from Rhodobacter Rb) sphaeroides, an electron is transferred from... 

Proton-coupled electron transfer (PCET) reactions play a vital role in a wide range of chemical and biological processes. For example, PCET is required for the conversion of energy in photosynthesis [1] and respiration [2], In particular, the coupling between proton motion and electron transfer is involved in the pumping of protons across biological membranes in photosynthetic reaction centers [1] and in the conduction of electrons in cytochrome c [3]. In addition to biological processes, PCET is also important in electrochemical processes [4, 5] and in solid state materials [6]. 

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