Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Morphing membranes: Cornell-led team makes first observation of essential cellular life process

23.10.2003


Cell membranes -- the sacs encompassing the body’s living matter -- can assume a variety of shapes as they morph to engulf materials, expel others and assemble themselves into tissues.


A giant unilamellar vesicle (GUV) designed to mimic so-called rafts of lipid segregation in cell plasma membranes, when examined under multiphoton fluorescence microscopy, reveals boundaries (in blue) between optically resolvable domains (red). The GUV, made of sphingomyelin, cholesterol and another phospholipid, is approximately 30 micrometers in diameter. Copyright © Nature. Photomicrograph by DRBIO/Cornell.



In the past it was possible for theoreticians only to analyze the thermodynamic forces behind membrane shape-shifting. But now a team of biophysicists from Cornell University, the National Institutes of Health and the W.M. Keck Foundation has been able to watch the sacs, or vesicles, reshaping themselves under the light of multiphoton three-dimensional microscopy. The forces behind the membrane morphing, the researchers say, is akin to a party entertainer shaping balloon animals by tensioning the surfaces.

Their report on observing the membranes -- a laboratory-grown mixture of phospholipids and cholesterol -- being reshaped into two separate, two-dimensional liquid phases, or "rafts,"


appears in the latest issue of the journal Nature (Oct. 23, 2003; vol. 425, pp. 821-824) and is illustrated on the magazine’s cover. The findings, say the researchers, should help cell biologists understand the functions of cell membranes that are important to human health.

"This is the first experiment to show interphase energetics influencing membrane geometries," says Cornell professor of applied physics Watt W. Webb, leader of the team. Tobias Baumgart, Cornell postdoctoral researcher, developed and analyzed the new experiments, and Samuel T. Hess of the National Institute of Child Health and Human Development, computed the theoretical shape "fits."

The interactions observed between separate phases of shape-shifting fluid membranes generally confirmed predictions made by German theoretician Reinhard Lipowsky and his colleagues. The observations also enabled measurement of the energetic tensions of the interphase lines separating the membrane rafts. In the immune system, defending macrophages engulf microbes and enclose the invaders in vesicles. "The same physical processes that we see in model membranes systems may be involved in controlling the budding and fission of these vesicles in cells," Baumgart says.

Molecular rafts of different compositions are believed to be involved in cell-membrane processes, Webb says, "but the physics of raft formation is not well understood. We hope our experiments -- based on 3-D-resolved multiphoton microscopy to illuminate membrane domains and transition behavior -- will encourage others to join in this study."

Baumgart emphasizes that balloon animals are not a perfect analogy for shape-shifting vesicles. "For one thing, rubber balloons stretch and vesicle membranes don’t, but seeing these shapes from a distance, we can imagine some of the same forces at work," he says.

Zooming in with the multiphoton microscope, Baumgart and his colleagues looked at a simplified model of cell membranes. In nature, vesicles are a complex mixture of several kinds of lipids, proteins and impurities; Baumgart’s laboratory-grown vesicles were made of just three kinds of lipids -- sphingomyelin, dioleylphosphatidylcholine and cholesterol. Fluorescent dyes that light up under the microscope’s laser beam were used to label different membrane phases either red or blue. The researchers found that, depending on the temperature, a cell membrane can have several fluid phases with different physical properties at the same time -- something like oil and water on the same surface.

Baumgart says the simplified vesicles produced a wide assortment of exotic shapes and structures as the temperature was changed, processes that appear to involve the disappearance of boundary-line tension as the two phases merge into a single one at higher temperatures.

The study was supported, in part, by a National Institutes of Health grant to the Developmental Resource for Biophysical Imaging Opto-Electronics (DRBIO) at Cornell and by a Keck Foundation grant to Baumgart. Multiphoton microscopy is a patented process developed at Cornell by Webb, who also is the Eckert Professor in Engineering and director of DRBIO, and by Winfried Denk, who now is a director at Germany’s Max-Planck-Institut für Medizinische Forschung Biomedizinische Optik.

The title of the Nature article is "Imaging coexisting fluid domains in biomembrane models coupling curvature and line tension."

Roger Segelken | Cornell news
Further information:
http://www.news.cornell.edu/releases/Oct03/Biomembrane.hrs.html
http://www.drbio.cornell.edu/

More articles from Life Sciences:

nachricht Toward a 'smart' patch that automatically delivers insulin when needed
18.01.2017 | American Chemical Society

nachricht 127 at one blow...
18.01.2017 | Stiftung Zoologisches Forschungsmuseum Alexander Koenig, Leibniz-Institut für Biodiversität der Tiere

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>