Nanotechnology molecular machine

Supposing that scientists succeed in constmcting molecular tools, they must overcome another obstacle for nanotechnology to be effective. A medical nanosubmarine is likely to contain about a billion (10 ) atoms. At an assembly speed of one atom per second, it would take 10 seconds to constmct one such device. That s almost 32 years If the assembly rate can be increased to one atom per micro-second, the constmction time for a 1-billion-atom machine drops to 1000 seconds, or just under 17 minutes. That s not bad if only a few machines are needed, but molecular machines are tiny, so large numbers of machines will be required for any practical application. Consequently, scientists will have to discover ways to mass-produce nanodevices. 

Another example of nanotechnology research is an attempt to develop biological molecules that can interact with fullerene, Cgo. By themselves, Cgo molecules are difficult to manipulate because they are greasy and inert. Scientists envision using proteins bound to Cgo, like the one illustrated here, as molecular machines that can deliver Cgo units to build larger carbon structures. 

Tweezers, scissors and screwdrivers are primitive tools compared to computers, but their importance and wide applicability to daily life cannot be ignored. Similarly, molecular scale mechanical devices would be very useful in nanotechnology. For example, a molecular robot that fabricates molecular wires and molecular machines that could penetrate deep inside the body would provide huge contribution in the fields of molecular electronics and medicine, respectively. 

Finally, even though the matter is beyond the aim of the present topic, a short mention is due to pseudorotaxanes, rotaxanes, catenanes and similar compounds (Refs. 299-303 and therein), to which conventional and/or unconventional hydrogen bridges confer peculiar characteristics making them extremely important in supramolecular and nanotechnologies chemistry for constructing molecular machines. 

The ultimate aim of nanotechnology is the development of self-assembling molecular-scale devices that can themselves perform specific, precisely controlled operations at the molecular and atomic level. Current methods nsing natnral molecular machines — proteins, enzymes, antibodies, and the like — or synthetic molecnlar forms still rely to a large degree on bulk processes. They provide us with rudimentary devices that operate at the molecular and atomic level, but at present they lack the precision and positional control reqnired to develop more advanced nanotechnologies. 

Keywords Molecular machines, Molecular switches, Molecular memory, Molecular computing, Supramolecular chemistry, Molecular optoelectronics, Command surfaces, Monolayers, Nanotechnology... 

The great demand for miniaturization of components in electrotechnical, medicinal or material applications has led to the development of a highly multidisciplinary scientific and technological field called nanotechnology to produce devices with critical dimensions within the range 1 100 nm. The ultimate solution to miniaturization is logically a functional molecular machine, an assembly of components capable of performing mechanical motions (rotation or linear translation) upon external stimulation, such as photoactivation.1103,1104,1239-1244 This motion should be controllable, efficient and occur periodically within an appropriate time-scale therefore, it involves photochromic behaviour discussed in the Special Topic 6.15. Such devices can also be called photochemical switches (Special Topics 6.18 and 6.15). Here we show two examples of molecular machines a molecular rotary motor and a molecular shuttle. 

Developments in nanotechnology have yielded nanomaterials for use in tissue engineering and facihtated the creation and study of nanoparticles and molecular machine systems that wiU assist in the detection and treatment of disease and injury. 

As the final topic of this chapter, the future-oriented approach of mechanically controlled DDS and sensing using molecular machines is presented. Molecular machines are certain kinds of state-of-the-art objects in current organic chemistry, supramolecular chemistry, and nanotechnology. A single molecule and/or a complex formed with a couple of molecules work as a machine in ultrasmall dimensions. However, most research efforts on molecular machines stay within the fine science level, and practical uses of molecular machines are still at the dream level. If we can control functions of molecular machines by conventional mechanical actions such as hand motions, it would open the way to common uses of molecular machines in daily life. In order to realize mechanical control of molecular machines, it would be required to couple two kinds of motions over very different length scales, that is, mechanical motions in meter or centimeter size and molecular motions in nanometer scale have to be combined. It can be rationally done if we use a two-dimensional medium where in-plane directions possess macroscopically visible dimensions and their thicknesses are maintained in the nanometer region [22]. Manual control of molecular machines can be accomplished at dynamic two-dimensional media. 

Destabilization of complexes upon redox stimulation tends to occur for a very practical reason. The redox center is usually involved in the specific noncovalent interaction that holds the complex together. Therefore, a fundamental change in its redox state removes some or all of the attractive interaction, making the complex unstable with respect to complexation that is, a net attraction is transformed into a net repulsion. At an intellectual level, this behavior has led to the creation of some exciting MIMs for use as artificial molecular machines (see Molecular Devices Molecular Machinery, Supramolecular Devices and Pho-tochemically Driven Moiecular Devices and Machines, Nanotechnology). 

Molecular machines and motors are molecules and molecular assemblies capable of converting chemical or physical input into mechanical movement. In nature, molecular machines play many essential roles—one example is ATPase. The power of molecular machinery where certain parts can be set into motion deliberately has triggered great interest in such machines in the course of the last decades because of their potential to also be leveraged in nonnatural molecules or molecular assemblies in nanotechnology. ... 

Artificial molecular machines are important not only for the study of the miniaturization of macroscopic machines but also for the growth of nanoscience and nanotechnology. Since the bottom-up approach has become the most promising method for chemists to construct nanoarchitectures and self-assembly has proved to be the most effective way to develop highly complicated chemical systems, realization of the movement at a single molecule level (synthetic molecular machines) has been considered to be a convenient way to construct complicated nanodevices. 

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