Science & Technology

Molecular machine boxing

Rotor design, synthesis, and function within Zn-PB. Credit: Institute for Basic Science

Machines trapped in cages or casings exhibit interesting properties by converting input energy into programmed functions. One such system is a mechanical gyroscope or gyro top. This is a fascinating toy that will entertain everyone with its constant rotation. Gyroscopes also have practical applications in internal navigation systems, virtual reality headsets, and wireless computer pointing devices used in airplanes and satellites. What makes these gyroscopes so useful is not only the rotor part, but also the frame that aligns the rotor in a particular direction. This restores the rotor’s momentum and protects it from obstacles.


In addition, everyday machines such as table fans and electric pumps also surround the rotor inside. cage-Something like a framework for separating them from the external environment.and Molecular levelBiological machines present in all living organisms also operate within cell confinement, exhibiting accurate and programmed movements and behaviors. These machines are remotely controlled by external stimuli. It is very difficult to synthesize such complex designs and functions with artificial molecular systems.

Currently, the team led by KIM Kimoon, director of the Self-Organization and Complexity Center of the Institute of Basic Sciences in Pohang, South Korea, is a supramolecular rotor that can be remotely controlled in a hollow cubic zinc (II) metallized porphyrin cage. Succeeded in building. (Zn-PB) molecule.Generally, the rotor is installed directly inside Molecular cage Due to the limited size of the cage window, it can be very difficult. Therefore, researchers followed a bottom-up strategy to prepare cages containing these rotors. To avoid these challenges, Kim et al. Devised a new strategy of first inserting the linear axle into the Zn-PB and then modifying it with the sidearms to build the rotor.

Molecular machine boxing

Remotely controlled rotation and tumbling motion of the rotor in the presence of chemical stimulants and photoresponsive molecules. Credit: Institute for Basic Science

Nothing is displayed with the rotor alone motionThe addition of the chemical stimulant initiates both rotational movement (rotation of the rotor arm around the axle) and rotational movement (rotation of the axle) at rotational speeds of 4000Hz and 1Hz, respectively. “We hypothesized that by using a simple reverse electron demand Diels-Alder (IEDDA) reaction without the use of a catalyst, we could easily add various functions to the axle without damaging the cage. By choosing the right arm for the, the controlled rotor can be designed to be started or stopped by external stimuli, “explains Avinash Dhamija, the first author of this study.

Previously, the same group constructed a 3D superstructure by connecting Zn-PBs by cross-linking ligands and fullerenes from outside the box cavity. These results have taken them one step further to explore the internal cavities of Zn-PB. Zn-PB has six Zn coordination sites capable of capturing polydentate molecules in the structure. Therefore, a two-seater linear axle was fixed in the cage, and then post-assembly changes were made to build a controllable rotor.

The authors also designed a pyridine-based photoresponsive molecule that can connect and cleave Zn-PB when exposed to UV and visible light, respectively. This allows reversible control of the double mechanical motion of the rotor. Controlling the rotor in this way is like a tug-of-war game. The pyridine derivative pulls the Zn center from the outside of the cavity and destroys the inside. rotor The connection initiates a 90 ° jump in a probabilistic way, like rotational and tumbling motions.

The current concept of confining molecular machines in molecular cages and remotely controlling their functions is useful not only for understanding the behavior of natural molecular machines, but also for developing smart and adjustable molecular devices. ..

The study was published in Chemistry..


Locked movement of molecular motors and rotors


For more information:
Kimoon Kim, a remotely controllable supramolecular rotor mounted inside a porphyrin cage, Chemistry (2022). DOI: 10.1016 / j.chempr.2021.12.008

Journal information:
Chemistry

Quote: Molecular Machine Boxing (January 18, 2022) was obtained from https: //phys.org/news/2022-01-molecule-machines.html on January 18, 2022.

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Molecular machine boxing

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