Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

How plants avoid feeling the burn

26.06.2006
Photoprotective effect measured for the first time at single biomolecule level

Too much sun – for plants as well as people – can be harmful to long-term health. But to avoid the botanical equivalent of "lobster tans," plants have developed an intricate internal defense mechanism, called photoprotection, which acts like sunscreen to ward off the sun's harmful rays.

"We knew that biomolecules called carotenoids participate in this process of photoprotection, but the question has been, how does this work?" said Iris Visoly-Fisher, a postdoctoral research associate in the Biodesign Institute at Arizona State University.

Carotenoids act as 'wires' to carry away the extra sunlight energy in the form of unwanted electrons, somehow wicking away the extra electrons across long distances from locations that could damage plant tissues and photosynthesis. During photoprotection, the consensus school of thought was that carotenoids--the source of the orange pigments in carrots and Vitamin A -- become oxidized, or charged, losing an electron in the process.

Now, Fisher and other ASU scientists have found a way to measure for the first time the electrical conductance within such an important biomolecule. And in doing so, the team has produced a new discovery which shatters the prevailing view. The research team found that oxidation is not required for photoprotection, but rather, carotenoids in a neutral, or uncharged state, can readily handle the electron overload from the sun.

Their findings have been published in the prestigious journal Proceedings of the National Academy of Sciences (PNAS) under the title"Conductance of a Biomolecular Wire" (http://www.pnas.org/cgi/content/abstract/0600593103v1).

"This is a remarkable experimental tour-de-force and the result is quite unexpected," said Lindsay, who directs Fisher's work in the Biodesign Institute's Center for Single Molecule Biophysics. "Carotene was regarded as the poster child for this molecular mechanism, but it turns out that a much simpler mechanism works just fine."

The innovative work was a collaboration between several ASU departments and the Univesidad Nacional de Rio Cuarto in Argentina. In addition to Fisher, who was lead author on the paper, contributions from chemistry and biochemistry professors Devens Gust, Tom Moore and Ana Moore of ASU's Center for the Study of Early Events in Photosynthesis were instrumental in the project.

"The initial interest was to more fully understand how photosynthesis works," said Fisher. Because our center focuses on electron transport in a single molecule, Devens Gust and Tom and Ana Moore suggested that we look at single molecule transport in carotene."

To get at the heart of the problem, Fisher had to attempt an experiment that had never been done before for any biomolecule: to control the charge of the biomolecule while measuring its ability to hold a current.

By holding a carotenoid under potential control, Fisher could control whether the biomolecule was in a neutral state or in the charged state (the oxidized state), while simultaneously measuring the electron transport through a single molecule.

"The importance of this result is not only for understanding natural systems and photosynthesis, but also for the fact that technically, for the first time, we could hold a molecule in a state pretty close to the natural conditions found in the plant," said Fisher.

To make the experimental measurements, Fisher first needed to work out several technically challenging variations to a method first pioneered by electrical engineering professor Nongjian Tao of ASU's Fulton School of Engineering. In concept, it's much like trying to measure the current of a wire found in an everyday household appliance, only in this case, the "wiring" is a miniscule 2.8 nanometers long and less than a single nanometer thick, or about 10,000 times smaller than the width of a human hair.

One measurement problem is that carotenoids are highly prone to react with water and oxygen, so all measurements had to be performed in an environment that would both protect the molecule and immerse it in an environment mimicking a biological cell membrane, where the carotenoids are found in nature.

Other innovations included developing a new insulating coat of polyethylene for the probe tip of a Scanning Tunneling Microscope (STM), which is used to measure the electron flow across single molecules. Also, the chemical ends of the carotenoids had to be modified so they could chemically stick to the STM probe's gold tipped electrodes.

To make a single measurement, the carotenoid molecules, which lie flat on the surface of a tiny reaction chamber, are first picked up by the STM probe's gold tip and chemically bound between these two electrodes, forming a kind of nanoscale bridge. "Gold is a soft metal, and when you pull it apart, eventually, you can measure the conduction of a single carotenoid molecule between the gold electrodes," said Fisher.

The research team found that, especially when compared to metals, carotenoids are not very conductive, even when measuring the most oxidized form. However, the electrical conduction was two orders of magnitude higher when compared to what is needed for the photoprotective effect to work.

The group also measured how fast the electrons traveled across the carotenoid bridge between the electrodes. By measuring carotenoids of different chemical lengths, the team showed that the travel rate was fast enough to match or exceed measurements performed in the plant system.

One of the greatest challenges of the experiment came down to the human endurance of taking thousands of measurements over an intense, six month period. "We needed to keep this finicky molecule away from the light, so sometimes, the microscope room became like a cave, where I was sitting for hours and hours in the dark," said Fisher.

For Fisher and the rest of the team, however, the main satisfaction was being able to break down a complex process to understand its simplest components and produce a groundbreaking discovery.

Joe Caspermeyer | EurekAlert!
Further information:
http://www.asu.edu

More articles from Life Sciences:

nachricht 'Y' a protein unicorn might matter in glaucoma
23.10.2017 | Georgia Institute of Technology

nachricht Microfluidics probe 'cholesterol' of the oil industry
23.10.2017 | Rice University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Salmonella as a tumour medication

HZI researchers developed a bacterial strain that can be used in cancer therapy

Salmonellae are dangerous pathogens that enter the body via contaminated food and can cause severe infections. But these bacteria are also known to target...

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

3rd Symposium on Driving Simulation

23.10.2017 | Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

 
Latest News

Microfluidics probe 'cholesterol' of the oil industry

23.10.2017 | Life Sciences

Gamma rays will reach beyond the limits of light

23.10.2017 | Physics and Astronomy

The end of pneumonia? New vaccine offers hope

23.10.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>