Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Seeing is bead-lieving

29.07.2014

Rice University scientists create model ‘bead-spring’ chains with tunable properties

Rice University researchers are using magnetic beads and DNA “springs” to create chains of varying flexibility that can be used as microscale models for polymer macromolecules.


DNA linkers serve as bridges between colloidal beads in a new experiment by Rice University scientists to study the physics of “bead-spring” polymer chains. They found the chains can be tuned for varying degrees of stiffness or flexibility. (Credit: Biswal Lab/Rice University)

The experiment is visual proof that “bead-spring” polymers, introduced as theory in the 1950s, can be made as stiff or as flexible as required and should be of interest to materials scientists who study the basic physics of polymers.

The work led by Rice chemical and biomolecular engineer Sibani Lisa Biswal and graduate student Julie Byrom was published this month in the American Chemical Society journal Langmuir. The researchers found the best way to study the theory was to assemble chains of micron-sized colloidal beads with nanoscale DNA springs of various lengths.

“Polymers are classically described as beads connected with springs,” Biswal said. “A lot of polymer physicists have come up with scaling laws and intuitive polymer properties based on this very simple concept. But there are very few bead-spring model systems that you can actually visualize.

That’s why this work came about.” Microscopic solids suspended in a liquid like the fat particles in milk or pigment particles in paint are examples of a colloidal system. Biswal said there has been great interest in creating colloidal molecules, and the Rice experiment is a step in that direction.

To make complex colloidal macromolecules, the researchers started with commercially available, iron-rich polystyrene beads coated with a protein, streptavidin. The beads are charged to repel each other but can connect together with springy DNA fragments. The chains formed when the researchers exposed the beads to a magnetic field. “We use the field to control particle positioning, let the DNA link the beads together and turn the field off,” Biswal said, explaining how the chains self-assemble.

“This is a nice system for polymers, because it’s large enough to visualize individual beads and positioning, but it’s small enough that thermal (Brownian) forces still dictate the chain’s motion.” As expected, when they made chains with short (about 500 base pairs) DNA bridges, the macromolecule remained stiff. Longer linkers (up to 8,000 base pairs) appeared to coil up between the beads, allowing for movement in the chain. Surprisingly, when the researchers reapplied the magnetic field to stretch the long links, they once again became rigid.

“Our vision of what’s happening is that DNA allows some wiggle room between particles and gives the chain elasticity,” Biswal said. “But if the particles are pulled far enough apart, you stress the bridge quite a bit and reduce the freedom it has to move.” Being able to engineer such a wide range of flexibilities allows for more complex materials that can be actuated with magnetic fields, Biswal said. “This research is interesting because until now, people haven’t been able to make flexible chains like this,” Byrom said.

“We want to be able to explain what’s happening across a broad range of polymers, but if you can only make rigid chains, it sort of limits what you can talk about.” Now that they can create polymer chains with predictable behavior, the researchers plan to study how the chains react to shifting magnetic fields over time, as well as how the chains behave in fluid flows. The paper’s co-authors are Rice alum Patric Han and undergraduate Michael Savory. The National Science Foundation supported the research.

Mike Williams | Eurek Alert!
Further information:
http://news.rice.edu/2014/07/28/seeing-is-bead-lieving/

Further reports about: DNA DNA fragments chains macromolecules materials models particles physics polymer macromolecules stiff

More articles from Materials Sciences:

nachricht Improving organic transistors that drive flexible and conformable electronics
06.05.2015 | University of Massachusetts at Amherst

nachricht Blending is the Trick: Tailored Pores in Block Copolymer Membranes
06.05.2015 | Helmholtz-Zentrum Geesthacht - Zentrum für Material- und Küstenforschung

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: The random raman laser: A new light source for the microcosmos

Texas A&M University researchers demonstrate how a narrow-band strobe light source for speckle-free imaging has the potential to reveal microscopic forms of life

In modern microscope imaging techniques, lasers are used as light sources because they can deliver fast pulsed and extremely high-intensity radiation to a...

Im Focus: Pulsar with widest orbit ever detected

Discovered by high school research team

A team of highly determined high school students discovered a never-before-seen pulsar by painstakingly analyzing data from the National Science Foundation's...

Im Focus: Erosion, landslides and monsoon across the Himalaya

Scientists from Nepal, Switzerland and Germany was now able to show how erosion processes caused by the monsoon are mirrored in the sediment load of a river crossing the Himalaya.

In these days, it was again tragically demonstrated that the Himalayas are one of the most active geodynamic regions of the world. Landslides belong to the...

Im Focus: Through the galaxy by taxi - The Dream Chaser Space Utility Vehicle

A world-class prime systems integrator and electronic systems provider known for its rapid, innovative, and agile technology solutions, Sierra Nevada Corporation (SNC) is currently developing a new space transportation system called the Dream Chaser.

The ultimate aim is to construct a multi-mission-capable space utility vehicle, while accelerating the overall development process for this critical capability...

Im Focus: High-tech textiles – more than just clothes

Today, textiles are used for more than just clothes or bags – they are high tech materials for high-tech applications. High-tech textiles must fulfill a number of functions and meet many requirements. That is why the Fraunhofer Institute for Silicate Research ISC dedicated some major developing work to this most intriguing research area. The result can now be seen at Techtextil trade show in Frankfurt from 4 to 7 May. On display will be novel textile-integrated sensors, a unique multifunctional coating system for textiles and fibers, and textile processing of glass, carbon, and ceramics fibers to fiber preforms.

Thin materials and new kinds of sensors now make it possible to integrate silicone elastomer sensors in textiles. They are suitable for applications in medical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Green Summit 2015: the summit of the essential

05.05.2015 | Event News

HHL Energy Conference on May 11/12, 2015: Students Discuss about Decentralized Energy

23.04.2015 | Event News

“Developing our cities, preserving our planet”: Nobel Laureates gather for the first time in Asia

23.04.2015 | Event News

 
Latest News

Two Activists in the Field of Energy Efficiency Awarded Swedish Sustainability Award

06.05.2015 | Awards Funding

Stanford researchers observe the moment when a mind is changed

06.05.2015 | Health and Medicine

U of T astrophysicists offer proof that famous image shows forming planets

06.05.2015 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>