Long polymer chains dance the conga

Mar 16, 2010
Researchers at the University of Illinois found that actin filaments (red) move in a path (blue) with an irregular diameter, instead of a cylinder as widely accepted. Credit: Bo Wang

Understanding the steps to the intricate dance inside a cell is essential to one day choreographing the show. By studying the molecules that give a cell its structure, University of Illinois researchers are moving closer to understanding one of those steps: the conga line.

Led by Steve Granick, Founder Professor of Engineering and professor of materials science and engineering, of chemistry, of chemical and biomolecular engineering, and of physics at the U. of I., the team published its findings March 16 in the online edition of journal .

Long chains of the molecule actin form filaments that are a key component of the matrix that give cells structure. They play a role in numerous cellular processes, including signaling and transport. Similar polymers are used in applications from tires to contact lenses to the gels used for DNA and protein analyses.

Long actin filaments display snakelike movement, but their serpentine wriggling is limited by crowding from other filaments in the matrix. Researchers have long assumed that could move anywhere within a confined cylinder of space, like a snake slithering through a pipe.

However, Granick and his research group have created a new model showing that the filaments' track isn't a perfect cylinder after all. Rather than a snake in a pipe, a filament moves more like a conga line on a crowded dance floor: Sometimes it's a tight squeeze.

To track the filaments' motion, the Illinois team used a novel approach. In the past researchers have observed the entire large molecule, which was like trying to figure out a conga line's trajectory by watching the entire crowd writhing on the dance floor.

"But," Granick said, "if I'm able to follow just one person in the crowd, I know a lot more about how the conga line is moving."

Granick and his team tagged a few individual links in the molecular chain with a tiny fluorescent dye and monitored how those moved as the slithered along. In the conga line analogy, this approach would be like giving neon shirts to a few people at various points in the line, turning on black lights, and tracking the neon-clad dancers' motion to map out the conga line's path around the floor.

"What we found is that, as the filaments slither, sometimes they're more free and sometimes they're more tightly tangled up with each other," Granick said. "Just like in a crowded place, you can only move through the empty spaces."

Next, the team will focus on further improving their model to include a molecule's forward motion as well as its lateral wiggling. "So far we've been able to see the conga line bending, moving sideways, and now we want to see it move in the direction it's pointing," Granick said.

"That's the missing link in completing this picture, which will lead to improved understanding of mechanical properties for all the situations where these filaments appear."

Explore further: Heat makes electrons spin in magnetic superconductors

Related Stories

Using a light touch to measure protein bonds

Jun 30, 2008

MIT researchers have developed a novel technique to measure the strength of the bonds between two protein molecules important in cell machinery: Gently tugging them apart with light beams.

How to Braid Nanoropes

Oct 14, 2005

Biomimetic systems that are composed of rigid polymers or filaments and crosslinking molecules can be used to assemble filament networks and bundles. The bundles represent 'nanoropes' and exhibit material ...

Janus particles offer new physics, new technology

Mar 13, 2006

In Roman mythology, Janus was the god of change and transition, often portrayed with two faces gazing in opposite directions. At the University of Illinois at Urbana-Champaign, Janus particles are providing ...

Rethinking Brownian motion with the 'Emperor's New Clothes'

Jul 27, 2009

In the classic fairy tale, "The Emperor's New Clothes," Hans Christian Andersen uses the eyes of a child to challenge conventional wisdom and help others to see more clearly. In similar fashion, researchers at the University ...

Recommended for you

Heat makes electrons spin in magnetic superconductors

Apr 24, 2015

Physicists have shown how heat can be exploited for controlling magnetic properties of matter. The finding helps in the development of more efficient mass memories. The result was published yesterday in Physical Review Le ...

ICARUS neutrino experiment to move to Fermilab

Apr 23, 2015

A group of scientists led by Nobel laureate Carlo Rubbia will transport the world's largest liquid-argon neutrino detector across the Atlantic Ocean from CERN to its new home at the US Department of Energy's ...

National security on the move with high energy physics

Apr 23, 2015

Scientists are developing a portable technology that will safely and quickly detect nuclear material hidden within large objects such as shipping cargo containers or sealed waste drums. The researchers, led ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.