Energy conversion membranes

In this paper, we will describe one of examples, where artificial archaeal glycolipids are applied to the construction of nano-devices containing energy-conversion membrane proteins, by employing the phytanyl-chained glycolipid we have recently developed, i.e., l,3-di-o-phytanyl-2-o- ((3-D-maltotriosyl) glycerol (Mab (Phyt)2, Fig. 1) [16,17] and natural proton pump, bacteriorhodopsin (BR) derived from purple membranes of the extremely halophilic archaeon Halobacterium salinarium S9 [18],... 

Anderson, J. M., and Andersson, B., 1988. The dynamic photosynthetic membrane and regulation of solar energy conversion. Trends in Biochemical Sciences 13 351 — 355. 

Liposomes have been widely used as model membranes and their physicochemical properties have therefore been studied extensively. More recently, they have become important tools for the study of membrane-mediated processes (e.g., membrane fusion), catalysis of reactions occurring at interfaces, and energy conversion. Besides, liposomes are currently under investigation as carrier systems for drugs and as antigen-presenting systems to be used as vaccines. 

In transport processes and information conservation In energy conversion and transfer In membrane structures and In signal transmission. 

Matzke, M. and Matzke, A.J.M. (2003). RNA extends its reach. Science, 301, 1060-1061 Mulkidjanian, A.Y., Cherepanar, D.A., Heberle, J. and Junge, W. (2005). Proton transfer dynamics at membrane/water interface and the mechanism of biological energy conversion. Biochem. (Moscow), 70, 251-256... 

Damle, A.S., Separation of Hydrogen and Carbon Dioxide in Advanced Fossil Energy Conversion Processes using a Membrane Reactor, 2002 Pittsburgh Coal Conference, Pittsburgh, PA, September 2002. 

In the case of 50 kW power, the rate of hydrogen supply needed (LH) is around 1.69 X 103 (mol/h) at the energy-conversion-efficiency level of 45% for the proton exchange membrane fuel cell (PEM-FC) [38]. 

Proton Exchange Membrane Fuel Cells (PEMFCs) are being considered as a potential alternative energy conversion device for mobile power applications. Since the electrolyte of a PEM fuel cell can function at low temperatures (typically at 80 °C), PEMFCs are unique from the other commercially viable types of fuel cells. Moreover, the electrolyte membrane and other cell components can be manufactured very thin, allowing for high power production to be achieved within a small volume of space. Thus, the combination of small size and fast start-up makes PEMFCs an excellent candidate for use in mobile power applications, such as laptop computers, cell phones, and automobiles. 

F-ATPases (including the H+- or Na+-translocating subfamilies F-type, V-type and A-type ATPase) are found in eukaryotic mitochondria and chloroplasts, in bacteria and in Archaea. As multi-subunit complexes with three to 13 dissimilar subunits, they are embedded in the membrane and involved in primary energy conversion. Although extensively studied at the molecular level, the F-ATPases will not be discussed here in detail, since their main function is not the uptake of nutrients but the synthesis of ATP ( ATP synthase ) [127-130]. For example, synthesis of ATP is mediated by bacterial F-type ATPases when protons flow through the complex down the proton electrochemical gradient. Operating in the opposite direction, the ATPases pump 3 4 H+ and/or 3Na+ out of the cell per ATP hydrolysed. 

The photosynthetic process thus provides us with an example of a complex, light-powered photochemical molecular device which uses light as an energy supply in order to facilitate energy conversion. In green plants, this molecular device is located within a specially-adapted photosynthetic membrane. 

We have seen that, in photosynthetic bacteria, visible light is harvested by the antenna complexes, from which the collected energy is funnelled into the special pair in the reaction centre. A series of electron-transfer steps occurs, producing a charge-separated state across the photosynthetic membrane with a quantum efficiency approaching 100%. The nano-sized structure of this solar energy-conversion system has led researchers over the past two decades to try to imitate the effects that occur in nature. 

PEFCs are an attractive alternative power source for mobile and stationary applications characterized by low emissions, good energy conversion efficiency and high power density. One of the main obstacles towards the commercialization of this technology is the high cost of component materials (catalyst, membrane, etc.) [160-162]. 

Nolte, R., Ledjeff, K., Bauer, M. and Miilhaupt, R. 1993. Partially sulfoanted PAES—A versatile proton conducting membrane material for modern energy conversion technologies. Journal of Membrane Science 83 211-220. 

The powerful biological machinery of energy conversion proceeds via redox reactions in aqueous media that involve electron and proton transfer between molecular entities. - Nature devised concerted sequences of these processes that generate electrochemical potential gradients across cell membranes and thereby enable the storage and the release of electrical energy. 

Enzymatic catalysis of reactions. Important enzymes are located in membranes at the interface between the lipid and aqueous phases. This is where reactions with apolar substrates occur. Examples include lipid biosynthesis (see p. 170) and the metabolism of apolar xenobiotics (see p. 316). The most important reactions in energy conversion—i.e., oxidative phosphorylation (see... 

General physiological roles for fatty acids in cellular lipids are caloric storage, membrane fluidity, and prostaglandin precursors. The first of these mainly involved the formation and hydrolysis of triacyl glycerols, transport and activation of non-esterified fatty acids, and other steps leading to energy conversion (110). The second role primarily involves activation and incorporation into 1- and 2- positions of different phospholipids which form a major part of membranes. The third role is linked to the requirement for certain unsaturated fatty acids in the diets of most animals (110). 

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