Molecular machine in nano cage

Date:
January 31, 2022
Source:
Ruhr-University Bochum
Summary:
Theoretical chemists have constructed a molecular gyroscope
that can be controlled remotely by light. They also succeeded
in characterizing the rotational movements of this synthetic
nanomachine with computer simulations.



FULL STORY ==========================================================================
In cooperation with an international team at the Institute for Basic
Science in South Korea, theoretical chemists Dr. Chandan Das and Professor
Lars Scha"fer from Ruhr-Universita"t Bochum (RUB) have constructed a
molecular gyroscope that can be controlled remotely by light. They also succeeded in characterising the rotational movements of this synthetic nanomachine with computer simulations.

The authors describe their findings in the journal "Chem," published
online on 18 January 2022.


========================================================================== Navigating aircrafts and satellites Machines enclosed in a cage
or casing may display interesting properties. For example, they can
convert their energy input into programmed functions. The mechanical
gyroscope is one such system -- an intriguing toy with the ability to
rotate continuously. Some practical applications of gyroscopes include
aircraft and satellite navigation systems and wireless computer mice,
to name but a few. "In addition to the rotor, another advantage of
gyroscopes is their casing, which aligns the rotor in a certain direction
and protects it from obstacles," describes Lars Scha"fer.

At the molecular level, many proteins act as biological nanomachines. They
are found in every biological cell and perform precise and programmed
actions or functions within a confined environment. These machines
can be controlled by external stimuli. "In the lab, the synthesis and characterisation of such complex structures and functions in an artificial molecular system presents a huge challenge," says Scha"fer.

Constructed like a ship in a bottle In collaboration with a team headed
by Professor Kimoon Kim at the Institute for Basic Science in Pohang,
South Korea, the researchers have succeeded in enclosing a supramolecular
rotor in a cube-shaped porphyrin cage molecule.

Typically, fitting a completed rotor into such cages is complicated by
the limited size of the cage windows. In an effort to overcome these limitations, the synthetic chemists in South Korea developed a new
strategy that first introduced a linear axis into the cage, which was
then modified with a side arm to construct a rotor. "It's reminiscent
of building a ship in a bottle," illustrates Chandan Das, who, together
with Lars Scha"fer, performed molecular dynamics computer simulations to describe the rotational motion of the rotor in the cage in atomic detail.

"Our collaboration partners made the intriguing observation that the
movement of the rotor in the cage could be set in motion and also
switched off again by light as an external stimulus, just like with a
remote control," describes Scha"fer. The researchers accomplished this
by using light in the UV and visible range to dock a photo-responsive
molecule to the cage from the outside and detach it again.

How the molecular gyroscope moves But how does it work, and what
movements does the molecular gyroscope perform after it's switched on
in this manner? "Molecular dynamics computer simulations show that the
rotor molecule in the cage exhibits stochastic dynamics, characterised by random 90-degree jumps of the rotor side arm from one side of the cube to
an adjacent side," as Chandan Das explains the results of the theoretical calculations, which can thus elucidate the spectroscopic observations.

The researchers hope that the concept of encasing molecular nanomachines
in a molecular cage and remotely controlling their functions will
contribute to the understanding of how biological nanomachines work and
to the development of smart molecular tools.

========================================================================== Story Source: Materials provided by Ruhr-University_Bochum. Original
written by Meike Driessen. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Avinash Dhamija, Chandan K. Das, Young Ho Ko, Younghoon Kim,
Rahul Dev
Mukhopadhyay, Anilkumar Gunnam, Xiujun Yu, In-Chul Hwang, Lars V.

Scha"fer, Kimoon Kim. Remotely controllable supramolecular
rotor mounted inside a porphyrinic cage. Chem, 2022; DOI:
10.1016/j.chempr.2021.12.008 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220131153308.htm

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