Motors, molecular

Rayment, 1., et al. Three-dimensional structure of myosin subfragment-1 a molecular motor. Science 261 5-58, 1996. 

Protein dynamics—the action of enzymes and molecular motors—provides the key to understanding the biochemistry of this cheetah and the grasses through which it runs. (Frank Lane/Parfitt/Tony Stone Images)... 

Motor proteins, also known as molecular motors, use chemical energy (ATP) to orchestrate all these movements, transforming ATP energy into the mechanical energy of motion. In all cases, ATP hydrolysis is presumed to drive and... 

Astnmian, R. D., and Bier, M., 1996. Mechanochemical coupling of die motion of molecular motors to ATP hydrolysis. Biophysical Journal 70 637-653. 

Engel, A., 1997. A clo.ser look at a molecular motor by atomic force microscopy. Biophysical Journal 72 988. 

In a film, the cooperative effort of the different molecular motors, between consecutive cross-linked points, promotes film swelling and shrinking during oxidation or reduction, respectively, producing a macroscopic change in volume (Fig. 18). In order to translate these electrochemically controlled molecular movements into macroscopic and controlled movements able to produce mechanical work, our laboratory designed, constructed, and in 1992 patented bilayer and multilayer103-114 polymeric... 

Figure 17. Molecular motor reverse conformational changes (mechanical energy) stimulated by oxidation or reduction of the polymeric chain, a) reduced chain b) oxidized chain.

Even though dynein, kinesin, and myosin serve similar ATPase-dependent chemomechanical functions and have structural similarities, they do not appear to be related to each other in molecular terms. Their similarity lies in the overall shape of the molecule, which is composed of a pair of globular heads that bind microtubules and a fan-shaped tail piece (not present in myosin) that is suspected to carry the attachment site for membranous vesicles and other cytoplasmic components transported by MT. The cytoplasmic and axonemal dyneins are similar in structure (Hirokawa et al., 1989 Holzbaur and Vallee, 1994). Current studies on mutant phenotypes are likely to lead to a better understanding of the cellular roles of molecular motor proteins and their mechanisms of action (Endow and Titus, 1992). 

Rayment, I., Rypniewski, W.R., Schmidt-Base, K., Smith, R., Tomchick, D.R., Benning, M.M., Winkelmann, D.A., Wesenberg, G., Holden, H.M. (1993). Three-dimensional strucmre of myosin subfiagment-1 A molecular motor. Science. 261, 50-65. 

The description of the motions of swimming bacteria like E. coli or molecular motors such as kinesin requires a knowledge of their propulsion mechanisms and the nature of the interactions between these micron and nanoscale objects and the surrounding fluid in which they move. These are only two examples of a large class of small self-propelled objects that one finds in biology. Propulsion occurs by a variety of mechanisms that usually involve the conversion of chemical... 

Dittrich M, Yu J, Schulten K (2007) PcrA Helicase, a Molecular Motor Studied from the Electronic to the Functional Level. 268 319-347 Dobrawa R, see You C-C (2005) 258 39-82... 

Kay ER, Leigh DA (2005) Hydrogen Bond-Assembled Synthetic Molecular Motors and Machines. 262 133-177... 

Figure 89 The motorized nanocar structure (172) that contains a light-activated unidirectional molecular motor and an oligo(phenylene ethynylene) chassis and axle system with four carboranes to serve as the wheels. (Adapted from ref. 168.)... 

To conclude this brief note (for details see texts of Biochemistry) we stress that the thermodynamic efficiency of molecular motors can be quite high, approaching 100% but never reaching this thermodynamic limit see Everett and also Neilson and Crawford in References to Appendix. We must always be aware of the heat losses in any real process and this is true all the way from the simplest molecular machines to multi-molecular constructs to man-made machines. 

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