Bacteriorhodopsin photosynthesis

Song, L., El Sayed, M. A., Lanyi, J. K., Protein Catalysis of the Retinal Subpicosecond Photoisomerization in the Primary Process of Bacteriorhodopsin Photosynthesis, Science 1993, 261, 891 894. 

It is interesting to compare the thermal-treatment effect on the secondary structure of two proteins, namely, bacteriorhodopsin (BR) and photosynthetic reaction centers from Rhodopseudomonas viridis (RC). The investigation was done for three types of samples for each object-solution, LB film, and self-assembled film. Both proteins are membrane ones and are objects of numerous studies, for they play a key role in photosynthesis, providing a light-induced charge transfer through membranes—electrons in the case of RC and protons in the case of BR. 

Proton gradients can be built up in various ways. A very unusual type is represented by bacteriorhodopsin (1), a light-driven proton pump that various bacteria use to produce energy. As with rhodopsin in the eye, the light-sensitive component used here is covalently bound retinal (see p. 358). In photosynthesis (see p. 130), reduced plastoquinone (QH2) transports protons, as well as electrons, through the membrane (Q cycle, 2). The formation of the proton gradient by the respiratory chain is also coupled to redox processes (see p. 140). In complex III, a Q,cycle is responsible for proton translocation (not shown). In cytochrome c oxidase (complex IV, 3), trans-... 

Light is indispensable for life. Green plants and some bacteria use solar energy for the energy source in their photosynthesis [1-3]. Archeal bacteriorhodopsin is a membrane bound protein and works as a light-driven proton pump [4, 5]. Another role of light is information carrier that is recognized in vision and photo-sensors. 

Non-Forster fluorescence quenching of trans-etiochlorin by magnesium oc-taethylporphine in phosphatidylcholine vesicles gives evidence for a statistical pair energy trap. Energy transfer also occurs in the excited singlet manifold of chlorophyll. " The photophysics of bis(chlorophyll)-cyclophanes, models of photosynthetic reaction centres, have been explored for use in artificial photosynthesis.Picosecond time-resolved energy transfer in phycobilosomes have also been studied with a tunable laser. The effect of pH on photoreaction cycles of bacteriorhodopsin, " the fluorescence polarization spectra of cells, chromatophores, and chromatophore fractions of Rhodospirillum rubrum, and a brief review of the mechanism and application of artifical photosynthesis are all relevant to the subject of this Chapter. 

So far all stimulatory processes of the halobacterial cell depend on fumarate as seen by the fact that smooth swimming mutant cells of strain M415 do not respond to any stimulus. This also holds true for the step-down photophobic response mediated by bacteriorhodopsin[5]. This points to the role of a central metabolite as an integrative tool for measurement of the metabolic state of the cell. Especially fumarate would allow us to measure and compare activity states of electron transport, fermentation and photosynthesis (see Fig. 2). 

A very different type of bacterial photosynthesis, which occurs only in certain archaebacteria, is not discussed here because it is very different from photosynthesis in higher plants. In this type of photosynthesis, the plasma-membrane protein bacteriorhodopsin pumps one proton from the... 

The second line of evidence relates to more recent metabolic innovations such as photosynthesis. LUCA, it seems, could not photosynthesize. No form of photosynthesis based on chlorophyll is found in any archaea. A completely different form of photosynthesis, based on a pigment called bacteriorhodopsin, similar to the photoreceptor pigments in our eyes, is practised by the so-called halobacteria, archaea that live in high-salt conditions. This mode of photosynthesis is not found in any bacteria. These disparate forms of photosynthesis presumably evolved indepen-dently in bacterial and archaeal lineages some time after the age of LUCA, and subsequently remained tied to their respective domains. If a metabolic innovation as important as photosynthesis did not cross from one domain to another, there is no reason to think that other forms of respiration would have done so. We should certainly be wary of postulating that respiratory genes crossed domains unless we have evidence that they did so and the evidence from evolutionary trees suggests that they did not. 

Charge recombination is a widely recognized phenomenon in photosynthesis and solar energy conversion research that, until recently, was less appreciated in bacteriorhodopsin research. Charge recombination dissipates... 

Our analysis of the possible role of the ERP suggests another attribute of intelligent materials that is, modular design of molecular functions. The ability of bacteriorhodopsin to bind protons from the cytoplasm upon light stimulation serves as a critical step in proton translocation. The same event in rhodopsin, however, may serve an entirely different function it triggers the cyclic GMP cascade. Thus, Nature could well have utilized a common design for vision and for photosynthesis (85). The same design principle may be implemented with completely different types of molecules or materials. On the other hand, the same molecular event may be exploited for different purposes. 

Purple membrane(PM) of the extreme halophile Halobacterium halobium is another efficient photosynthetic system.Upon the absorption of visible light the unique protein of this membrane,bacteriorhodopsin (BR),undergoes a complicated photocycle and extrudes protons from the cell interior against their concentration gradient across the membrane.The free energy associated with this electrochemical gradient is used to transform ADP into ATP in the final step of photosynthesis (1,2). 

The application of femtosecond lasers to the investigation of important biological processes, such as the photosynthesis or the visual process, has brought a very detailed understanding of the different steps between the photoexcitation and the final product of this processes [15.144]. For example, the primary reaction of sensory rhodopsin after the excitation of the Si state is the decay with a time constant of 4 ps into a redshifted photo product, while bacteriorhodopsin decays much faster with a time constant of 500 fs. The pop-... 

Attention is focused on carotenoids and polyenes, which are known to be chemically very unstable as isolated entities but to acquire great stability when they are suitably surrounded by a protein cage and become the active elements in the mechanism of vision and photosynthesis. The CL dependence of the in situ Raman spectra of the carotenoids as naturally occurring pigments in bird feathers was studied by Veronelli et al. [65]. Later attention was focused on the bacterial membrane protein bacteriorhodopsin (bR). a small protein (—26,000 daltons) whose potential application in optical and electro-optical devices has been explored by many authors. The justification of such interest lies in the fact that bR contains all-/rfl/ .v retinal, which acts as a lightabsorbing center and makes bR a naturally reversible photochromic system. All-optical switching can be achieved by proper illumination of bR with yellow or blue light. 

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