Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Phase transition in bilayers could affect their performance

22.11.2002


Phospholipid bilayers that mimic cell membranes in living organisms are of interest as substrates for biosensors and for the controlled release of pharmaceuticals. To better understand how these materials behave with embedded proteins, a necessary first step is to understand how the bilayers respond by themselves.



As will be reported in the Dec. 9 issue of Physical Review Letters (published online Nov. 21), scientists at the University of Illinois at Urbana-Champaign have studied the phase transition in a supported bilayer and discovered some fundamental properties that could affect the material’s performance in various applications.

"Like water turning into ice, bilayers can exist in either a fluid phase or a solid (gel) phase, depending upon temperature," said Andrew Gewirth, a professor of chemistry. "Using a sensitive atomic force microscope, we studied how the microstructure of these bilayers changed during the transformation process."


First, the scientists supported a phospholipid bilayer on a piece of exceptionally smooth mica. Then they studied the properties of this bilayer as it changed phases from fluid to gel and back to fluid. Because touching the surface would destroy the delicate film, the researchers used a noncontact mode in which they oscillated the probe tip in close proximity to the surface, and measured the resulting change in amplitude.

"The atomic force microscope images showed that the fluid to gel phase transition produced substantial tearing of the bilayer, resulting in numerous big, foam-like defects," Gewirth said.

Because the mica substrate was molecularly smooth with no significant surface defects, the scientists concluded that the rips and tears were caused by an intrinsic property of the phase transition itself.

"The gel phase is more dense than the fluid phase," Gewirth said, "so the defects are likely caused by the change in density and, to a lesser extent, by thermal contraction."

As the material solidified, it became highly strained as a consequence of the large density difference between the two phases, Gewirth said. When the membrane was melted again, stress was released in places the scientists hadn’t expected: The melting began in areas other than the defects. In fact, the defects were the last to change back to the fluid phase, because the strain had been removed in the defects as a result of the tearing process.

"The bottom line is that history matters," said Steve Granick, a professor of materials science, chemistry and physics. "The method of preparing the gel phase strongly affects the resulting defect structure, and this in turn has considerable impact on the subsequent gel to fluid transition."

The presence of the defects poses a few problems, but also offers some opportunities, to making and using the bilayers. In biosensors, for example, the defects could affect both device performance and long-term storage characteristics.

"These biosensors would normally be used with the membrane in the fluid phase, but they would be stored in the gel phase," Granick said. "The defects that form as the material solidifies could cause the membrane to respond differently than was expected. As a result, the sensor might not detect the chemical it was designed for."

On the other hand, the defects could be useful as sites for modifying the properties of supported bilayers through the incorporation of additional constituents, the scientists said. In this case, the defects would serve as portals through the membrane, where proteins or other components could be introduced, and then encased by raising the temperature.

"Our experiments have shown that these phospholipid bilayers are a lot more complicated than most people realized," Granick said. "There are many complex materials processing issues that must be considered when making and using them."

Collaborators on the project were graduate student Anne Xie and postdoctoral researcher Ryo Yamada. The U.S. Department of Energy funded the work through a grant to the Frederick Seitz Materials Research Laboratory on the Illinois campus.

Jim Kloeppel, Physical Sciences Editor
(217) 244-1073; kloeppel@uiuc.edu

James E. Kloeppel | UIUC news bureau
Further information:
http://www.news.uiuc.edu/scitips/02/1121phasetransition.html
http://www.scs.uiuc.edu/

More articles from Life Sciences:

nachricht Researchers identify potentially druggable mutant p53 proteins that promote cancer growth
09.12.2016 | Cold Spring Harbor Laboratory

nachricht Plant-based substance boosts eyelash growth
09.12.2016 | Fraunhofer-Institut für Angewandte Polymerforschung IAP

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Electron highway inside crystal

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.

Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Researchers identify potentially druggable mutant p53 proteins that promote cancer growth

09.12.2016 | Life Sciences

Scientists produce a new roadmap for guiding development & conservation in the Amazon

09.12.2016 | Ecology, The Environment and Conservation

Satellites, airport visibility readings shed light on troops' exposure to air pollution

09.12.2016 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>