Unexpected moves from polymer chains


Rebecca Pool

Thursday, January 24, 2019 - 13:00
Image: Super-resolution fluorescence microscopy (right) produces significantly sharper images compared to conventional fluorescence microscopy.[Abadi et al.]
Using super-resolution fluorescence microscopy with custom particle tracking, researchers from Saudi Arabia have studied the motion of individual molecules within a polymer.
Their latest observation challenge current thinking about polymer physics and could lead to new materials that can be tailored for specific tasks.
Until now, researchers' ability to fully understand polymer properties was hampered because it was impossible to observe individual polymer chain motion.
But as Maram Abadi from Satoshi Habuchi's research team, KAUST, highlights: "Fluorescence imaging is an excellent technique to capture real-time behaviour of dynamic systems.
With this in mind, Abadi and colleagues created a polymer with fluorescent tags attached at several points along the chain.
Using super-resolution fluorescence imaging, they captured some 10,000 images within a few seconds, that were then combined to generate a single super-resolution image. 
By combining this method with a custom single-molecule tracking algorithm, they showed that the polymer dynamics were more complex than previously thought.
A new technique developed by Maram Abadi (left), Satoshi Habuchi and colleagues challenges current thinking about polymer physics. [KAUST]
"Here we have developed a new single-molecule characterization platform by combining super-resolution fluorescence imaging and recently developed single-molecule tracking method, cumulative-area tracking," writes Abadi in Nature Communications. "This enables [us] to quantify the chain motion in the length and time scale of nanometres to micrometres and milliseconds to minutes."
As the researcher points out, past models using 'reptation theory' indicated that the entire polymer chain moves as a single unit, similar to a snake.
However, the latest results reveal that the polymer actually undergoes chain-position-dependent motion, with most motion occurring at the chain ends and the least motion occurring in the middle.
"Since rheological properties of materials arise microscopically from entangled polymer dynamics, a revision of the reptation theory would have a broad impact not only on fundamental polymer physics but also on the development of a wide range of polymer nanomaterials," says Abadi.
The researchers now plan to apply their technique to more complex systems, including polymer gels and networks of biomolecules within cells.
Research is published in Nature Communications.
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