Single-Molecule Unidirectional Processive Movement along a Helical Polymer Chain in Non-aqueous Medium.

Area of Science:

• Polymer Chemistry
• Nanotechnology
• Molecular Machines

Background:

• Synthetic polymers can be designed with specific architectures to act as nanoscale tracks.
• Molecular motors are crucial for developing artificial systems that mimic biological functions.
• Chiral helical polymers offer unique structural properties for controlled molecular movement.

Purpose of the Study:

• To observe and characterize the unidirectional movement of a molecule along a synthetic polymer chain.
• To investigate the mechanism driving this molecular motion.
• To propose a principle for a polymer-based molecular motor.

Main Methods:

• Utilizing a fast-scanning atomic force microscope (AFM) to visualize macromolecular motion.
• Employing all-atom molecular dynamics (MD) simulations to model the observed phenomenon.
• Designing a chiral helical polymer (substituted phenylacetylene with cholesteryl groups) as a nanoscale rail.

Main Results:

• Observed unidirectional, processive movement of a short-chain molecule along the polymer rail in 3 nm steps.
• Demonstrated that movement is driven by Brownian motion and AFM tip tapping via a flash ratchet mechanism.
• Confirmed van der Waals interactions facilitate movement along the chiral helical polymer.

Conclusions:

• Proposed the principle of a novel polymer molecular motor.
• Reported the first synthetic walking machine based on a chiral helical polymer driven by thermal fluctuation.
• Established a new artificial life function at the molecular level.