Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Atomic force microscopy : How cell membranes respond to their environment

01.08.2005


Organization of membrane proteins… Membrane organization in photosynthetic bacteria – observed by atomic force microscopy –exposed to strong light. The light-harvesting complexes (small circles) alternate geometrically with the reaction centers (large rings with central density) which manage the light energy. The reaction centers are organized so as to manage light energy, when light is strong.


Some 25% of genes code for membrane proteins. Yet membrane organization remains a mystery. Membranes envelop all the cells in our bodies, forming a natural barrier, the membrane proteins within these can also recognize certain cells and direct a drug to them.

Using atomic force microscopy, Simon Scheuring (Inserm), in a CNRS unit at the Institut Curie, and James N. Sturgis, professor at the Université de la Méditerranée (CNRS unit), have studied the organization of a bacterial membrane and how it adapts in response to external factors. This is the first time that the inner workings of a membrane have been unveiled. Scheuring and Sturgis show that the organization of membrane proteins is not fixed but can vary with membrane location and time. This work was published in the July 15, 2005 issue of Science.

The body’s innumerable cells with their specialized tasks contain organelles, which perform particular functions. If they are to operate efficiently in the right location, organelles and cells alike must be suitably differentiated and above all isolated. This is the role of the lipid bilayers that constitute membranes.



But membranes are not simple barriers, they also act as border guards, assisted by membrane proteins which oversee the comings and goings between the cell and the outside world. Membranes also relay information across the cellular divide and so are essential for communication between cells and their environment. Informative messages from outside the cell (other cells, tissues and organs) are received by membrane receptors, which activate proteins within the cell, which in turn activate other proteins, and so forth, until there is a genetic response. Once decoded, these signals enable cells to determine their position and role within the body. The signals are essential for the proliferation, differentiation, morphology and mobility of cells and for key cellular functions. These signals ensure that the size and function of organ tissues are maintained harmoniously.

Nearly 70% of drugs target membrane proteins(1)

Observing protein supercomplexes

Membrane proteins generally do not operate in isolation but instead combine to form protein supercomplexes. One of the best known complexes transforms light energy into ATP(2) in photosynthetic bacteria such as Rhodospirillum photometricum (see box). Atomic data on these various membrane components are relatively abundant, but until now information on the organization of these complexes has been scarce because we have lacked suitable tools.

Exploring the depths of the cell by atomic force microscopy

Simon Scheuring and James N. Sturgis have recorded high-resolution images of biological membranes under physiological conditions using atomic force microscopy, a technique developed by physicists in 1986, which provides atomic resolution images of a sample’s surface. An atomically sharp tip is scanned over the sample surface and its movements are tracked by a laser. The resulting data can be used to draw a topographical map of the sample.

Atomic force microscopy has the enormous advantage of being able to analyze samples in solution, which is a major asset for biology. Since 1995, membrane proteins have been studied by atomic force microscopy at a lateral resolution of 10 Angstroms and vertical resolution of 1 Angstrom (one ten thousand millionth of a meter). This has now defined the contours of many membrane proteins that work together in native membranes – i.e. membranes close to their natural state – thereby revealing their organization.

In photosynthetic bacteria, membrane organization changes with the intensity of incident light. In dim light, the proportion of light-harvesting complexes is higher. The reaction centers “manage” the harvested light and minimize losses. Lost light may induce the formation of free radicals that damage DNA and proteins and the bacterium itself in the longer term.

Membranes respond to the environment and adapt their organization as required. These results confirm that membranes are not homogeneous: a given membrane has several possible compositions (variable position and quantity of lipids and membrane proteins). Researchers have used this example to study general aspects of membrane organization.

In addition to enhancing our understanding of photosynthesis in bacteria, these findings amply demonstrate the value of atomic force microscopy in observing proteins in native membranes on the nanometer scale (i.e. one millionth of a millimeter). Simon Scheuring penetrates the depths of these protein complexes by observing them in situ and under physiological conditions.

Cells will progressively yield up their secrets as they are explored using a combination of high-resolution imaging, as in atomic force microscopy, optical microscopy and electron microscopy.

Catherine Goupillon | alfa
Further information:
http://www.sciencemag.org/
http://www.curie.fr

More articles from Life Sciences:

nachricht What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

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...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

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

Simple processing technique could cut cost of organic PV and wearable electronics

06.12.2016 | Materials Sciences

3-D printed kidney phantoms aid nuclear medicine dosing calibration

06.12.2016 | Medical Engineering

Robot on demand: Mobile machining of aircraft components with high precision

06.12.2016 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>