Molecular motors are nano-scaled structures that are likely to prove especially valuable in the emerging field of nanotechnology. The overall significance of nano-scaled motors to nanotechnology is comparable to the impact of the engine in modern society. The ability to harness and utilize, to both construct and deconstruct, these motors has the potential to expand and revolutionize the field of nanotechnology.
FIG. 2 presents a schematic illustration of the Technion Research & Development Foundation Ltd.crystal structure of an exemplary host-guest insertion complex Complex 4a, featuring a bis-imidazole dialkyne (Compound 4) inserted in a CB[6] (Compound 1), showing the centrosymmetric positioning of the guest molecule inside the cucurbituril host.
FIG. 3 presents a schematic illustration of the crystal structure of an exemplary host-guest insertion complex: Complex 5', featuring N-6-pyrrolidinium-hexa-2,4-diynyl ammonium dichloride (Compound 5') inserted in a CB[6] (Compound 1)..
In U.S. Patent Application 20100016610, Technion Research & Development Foundation Ltd. (Haifam, IL) inventor Ehud Keinan developed rotaxane consisting of a cucurbituril and an uncharged guest molecule, having low or null affinity therebetween i as well as processes for providing the same. It has various uses as energy converters ("frictionless" molecular motors) and in biochips and biosensors. The rotor can be fitted with different components that can be affected by external source(s) of energy to drive the molecular motor,
By interacting with such an external source of energy or force, the rotaxane, which the effector moiety is attached thereto, can act as an energy converter which can transform one form of energy to another form of energy. The effector moiety is capable of absorbing electromagnetic radiation in the microwave range, and cause the host and the guest of the rotaxane to rotate with respect to one-another, thereby converting the electromagnetic radiation energy to rotational kinetic energy, which in turn can be converted to heat (translational kinetic energy).
In another example, the effector moiety includes a paramagnetic metal which interacts with an external magnetic force field, and cause the host and the guest of the rotaxane to rotate with respect to one-another, thereby converting the magnetic force field to rotational kinetic energy, which in turn can be converted to heat (translational kinetic energy).
Such energy converters based on the rotaxane presented by Keinan constitute a "frictionless" molecular motor. The motor attribute stems from the capacity to convert one source of energy to rotational energy and vice-versa, and the frictionless attribute arises from low affinity or lack thereof between the stator, namely the cucurbituril host molecule, and the rotor, namely the guest molecule.
Synthetic molecular motors, which are not based on proteins, have been theorized and hypothesized in the past decades. Most of the reported efforts to synthesize molecular rotary motors, including bevel gears, propellers, a three-propeller system, and molecular turnstiles have exploited intramolecular interactions with one molecular fragment rotating with respect to the rest of the molecule around one or two single bonds.
One of the most challenging design elements of molecular rotary motors is their requirement of a unidirectional motion. Attempts to meet this challenge have resulted in various stepwise (non-continuous), unidirectional moving devices, including light-driven, chemically driven and electrically driven machines.
