Supramolecular motor

F. Diotallevi and B. M. Mulder, The cellulose synthase complex A polymerization driven supramolecular motor, Biophys. J., 92 (2007) 2666-2673. 

Of particular interest with respect to applications in nanotechnology is the rotary supramolecular motor, FoFi-ATP synthase (Figure 1) (S). This enzyme is actually a double rotary motor. Proton flux across the membrane drives rotation of the Fo unit and the y spindle of the Fi unit. Rotation of the y spindle within the stationary Fi unit, in turn, drives the synthesis of ATP from ADP and inorganic phosphate. While the rotary motion of this device qualifies it as a motor, this motion is merely a mechanism, enabling its biological function as a factory for a ubiquitous fuel needed by cells. 

Molecular and supramolecular devices incorporated into ultra-micro-circuits represent potential hardware components of eventual systems that might qualify as molecular computers, whose highly integrated architecture and operation would not be of the von Neumann type. On the biological side, the fabrication of components for sensory and motor protheses could be considered. All these entities may result from the self-assembly of suitably instructed subunits so that computing via self-assembly may be envisaged. 

Intelligent molecular systems can be created based on host-guest recognition, which can self-organize and behave differently than nonorganized matter. Supramolecular structures formed by molecular recognition can be used to create molecular systems with specific functions, such as motors or stimulus-responsive... 

Functional electrochemically controlled supramolecular machines based on CyD units now being actively studied and already presenting motor-like behavior on the molecular level, following new routes in the bottom-up approach, should soon enter the world of useful micro- and mesoscale electromechanical devices. This subject is discussed in Chapter 16. 

Synthetic molecular motors and mechanical machines (in particular, supramolecular complexes of porphyrins, crown ethers, cavitands, rotaxanes, catenanes, and other macroheterocycles) 07AG(E)72. 

Figure 14. Simplified scheme of protein-protein interactions that transduce the sensory signal from the receptor supramolecular complex to the flagellar-motor supramol-eoular complex. Black arrows stand for regulated interactions. The scheme is not drawn to scale. (Taken with permission from Bren and Eisenbach [137].)...

CheY, perhaps the most investigated Che protein, is a multifunctional, key response regulator whose role is to bridge between two membrane-associated, supramolecular complexes the receptor complex and the switch-motor complex (Figure 14). As will be discussed in Section 8.2, its main role is to shift, in response to signals received from the receptors, the direction of flagellar rotation from the default direction, counterclockwise, to clockwise. This role is fulfilled by the following specific functions. 

Keywords AFM Desorption Inherent elasticity Macromolecules Mechanochemistiy Molecular motor Non-covalent interactions Polymer models QM calculations Single-molecule elasticity SMFS Supramolecular chemistry Supramolecular polymer Water rearrangement... 

A supramolecular device is a molecular-level system that acts or carries out a function of some kind in the same way as a larger-scale device, such as an electronic component (switch, rectifier) or mechanical object (motor, spring). The basis for the device s operation can be supramolecular in the sense that two or more components interact in a noncovalent manner. This is the case with rotaxane 13 (Fig. 7), in which the paraquat-derived macrocycle switches back and forth between the two biaryl "stations" in response to changes in pH. The interaction between the paraquat "train" and the two stations on the polyethyleneglycol "track" is entirely supramolecular and involves n-stacking. charge transfer, and CH-. O hydrogen bonds. 

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