Protein-based machines membrane

The protons, now at 1,000-fold higher concentration in the thylakoid lumen than in the surrounding stroma, return across the thylakoid membrane from lumen to stroma and produce the chemical energy ATP by means of the protein-based machine ATP synthase, briefly considered below and in some detail in Chapter 8. 

The 1,000-fold greater concentration of protons (acid) of the intermembrane space return across the inner mitochondrial membrane and produce chemical energy, in the form of ATP. As in photosynthesis, the ATP results from the protein-based machine ATP synthase. 

Protein-based Machines in the Thylakoid and Inner Mitochondrial Membranes... 

A flow of electrons in a series of cell membrane-associated oxidation and reduction cycles provides the energy source in the energyconverting thylakoid membranes of plants and inner mitochondrial membranes of plants and animals. In the process of this electron flow, membrane proteins pump protons across a cell membrane to increase the concentration of protons on one side of the membrane (to be considered in Chapter 8). Another protein-based machine uses the high concentration of protons on one side of a cell membrane to drive the formation of ATP as the protons pass to the low concentration side of the membrane (also to be considered in Chapter 8). 

One of the more challenging locations, therefore, for consideration of the comprehensive hydrophobic effect in the panoply of biological energy conversions is the electron transport chain embedded within the inner mitochondrial membrane. Essential parts of these protein-based machines insert into and function in very hydrophobic lipid bilayers. Here the ingress and egress of protons for develop-... 

In general, then, the energy conversions of biology reduce to the production of ATP and the uses of ATP, that is, the production of ATP by the five protein-based machines of the inner mitochondrial membrane and the thousands of subsequent protein-based machines that do the necessary work of the cell. This constitutes yet an enormous task that will fill hundreds of volumes in the future of protein-based machines. The intention of this volume, however, is to add a simplifying feature of a common groundwork of explanation for each of the hydrophobic and elastic consilient mechanisms. For the function of protein-based machines of biology, this perspective recovers an attractive element of simplification. 

The protons are released to one side of an otherwise generally proton-impermeable inner mitochondrial membrane to collect the protons in the space between the inner and outer membranes of the mitochondrion. The resulting proton concentration gradient then drives formation of ATP by the quintessential protein-based machine, ATP synthase, as the protons flow back through the inner mitochondrial membrane by means of another special path effecting proton permeability. Thus there are two fundamental questions. The first is, how does electron flow within the membrane achieve unidirectional proton flow across the membrane The second is, how does the return flow of protons result in the formation of ATP, the energy coin of biology ... 

The concept of two distinct but interlinked mechanical processes, expanded here as the coupling of hydrophobic and elastic consilient mechanisms, entered the public domain in the publication of Urry and Parker. Experimental results on elastic-contractile model proteins forged the concept, and the work of Urry and Parker extended the concept to contraction in biology. Unexpected in our examination of the relevance of this perspective to biology was to find the first clear demonstration of the concept in biology in a protein-based machine of the electron transport chain as a transmembrane protein of the inner mitochondrial membrane. Unimaginable was the occurrence of the coupled forces precisely at the nexus at which electron transfer couples to proton pumping. 

Beck, K. A. and Nelson, I. The spectrin-based membrane skeleton as a membrane protein-sorting machine. Am.. Physiol. 270 C1263-C1270,1996. 

Protein is an excellent natural nanomaterial for molecular machines. Protein-based molecular machines, often driven by an energy source such as ATP, are abundant in biology. Surfactant peptide molecules undergo self-assembly in solution to form a variety of supermolecular structures at the nanoscale such as micelles, vesicles, unilamellar membranes, and tubules (Maslov and Sneppen, 2002). These assemblies can be engineered to perform a broad spectrum of functions, including delivery systems for therapeutics and templates for nanoscale wires in the case of tubules, and to create and manipulate different structures from the same peptide for many different nanomaterials and nanoengineering applications. 

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