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!
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
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...
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...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.
Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
16.01.2017 | Trade Fair News
16.01.2017 | Architecture and Construction
13.01.2017 | Life Sciences