Physicists look to navigational ‘rhumb lines’ to study polymer’s unique spindle structure


Plots of the loxodrome design, which demonstrates how the spheres shift into an extended shape. (Image credit: Helen Ansell) Credit: Helen Ansell

From the elaborate patterns of pollen grains to the logarithmic spirals of nautilus shells, biology has lots of complex patterns, shapes, and geometries. A lot of these elaborate structures play crucial functions in biological function, however can be hard to produce in a laboratory without modern devices or pricey and energy-consuming procedures and products.


A brand-new study explains how spheres can be changed into twisted spindles thanks to insights from 16th century navigational tools. Scientists demonstrate how polymers can contract into spiral structures, called loxodromes, that have intricate pattern 10 times smaller sized than the width of a human hair. Released in Physical Evaluation Letters, the research study was performed by University of Pennsylvania college student Helen Ansell, postdoc Daeseok Kim, and teachers Randall Kamien and Eleni Katifori in the School of Arts and Sciences, in cooperation with Teresa Lopez-Leon of the École Supérieure de Body et de Chimie Industrielles de la Ville de Paris (ESPCI).

Kim, who dealt with this task at ESPCI prior to coming to Penn, was influenced by other research studies revealing that a mix of polymer and liquid crystal handled a brand-new shape when positioned in a various solvent. It was a modification that was likewise reversible and reproducible, with little to no energy needed to trigger the modification fit.

To comprehend the fascinating conformational modifications that Kim had actually seen in the laboratory, he looked for theorists who might assist understand how the polymer’s geometry triggered it to twist and agreement. After seeing the tiny images and information that was gathered and examined by Kim, Ansell had a preliminary concept of what the spindle’s structure may be: a loxodrome.

More typically referred to as rhumb lines, a loxodrome is an arc that follows a consistent angle as it crosses a sphere. Sailors throughout the 16th-19th centuries utilized these lines to browse, permitting them to set their compasses to a consistent bearing so that their ship did not have to alter its bearing.

“We tried to figure out if this was the case,” Ansell states about examining if her hypothesis was appropriate. “We think we found these loxodromes, so we had to go about comparing what does it look like versus the data.”

Ansell then established a mathematical design that explains how the spheres end up being extended and twisted utilizing the geometry of the loxodrome as a beginning point. By comparing the outcomes of her theory to the information produced by Kim, she was able to reveal that altering the solvent triggered the polymers to diminish, which triggered its shape to twist as the polymer chains along the sphere’s lines of longitude ended up being much shorter.

Physicists look to navigational 'rhumb lines' to study polymer's unique spindle structure
Scanning electron microscopic lense images revealing polymers in a round setup (far left); when a brand-new solvent is included, the spheres twist and become extended twisted spindles (far best). At the top of the spindles (center panel) are one micron spirals. (Image: Daeseok Kim) Credit: Daeseok Kim

At the top of the spindles are one micron spirals, almost one hundred times smaller sized than the width of a human hair. Producing manmade patterns that little typically needs expensive approaches and devices, however this technique of making self-assembled small structures utilizing course-scale beginning products is much easier.

The polymer loxodrome is the most recent finding that looks into the Kamien group’s interests in the crossover in between chemistry and geometry. Kamien states that lots of interactions in biology, like protein folding, immune reactions, and even odor, is typically illustrated as a chemical bond, however stresses that geometry likewise drives much of what occurs in biology.

“Think about proteins,” states Kamien, “You have these different amino acids, and they attract in different ways, but when you’re all done, you have this giant glob, and there’s this little pocket that grabs the residues, so you think of it geometrically. Helen’s explanation is completely geometrical: It doesn’t involve anything specific about how the binding works.”

For Kim, this research study is an interesting initial step for studying unique structures in other biological systems. By creating brand-new kinds of polymer particles and checking them out in various conditions, he hopes to find out more about how shape drives function, specifically in systems that twist and agreement. “We could study some biological matter in nature by mimicking a similar topological model,” he states, “And we may solve or study some complex problem in nature.”

Now, totally coincidentally, Ansell’s efforts have actually prepared for another unassociated task she had actually been stuck on for a long time which likewise appears to have a loxodrome option.

“They just appear,” she states about the twisted spindle shape.

“As Pasteur said, luck favors the prepared mind,” includes Kamien. “Now, we’re primed to look for them.”


Scientists show how to control liquid crystal patterns


More info:
Helen S. Ansell et al, Threading the Spindle: A Geometric Study of Chiral Liquid Crystal Polymer Microparticles, Physical Evaluation Letters (2019). DOI: 10.1103/PhysRevLett.123.157801

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Physicists look to navigational ‘rhumb lines’ to study polymer’s unique spindle structure (2019, October 11)
obtained 11 October 2019
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