Featured Research

from universities, journals, and other organizations

How Nature Harvests Sunlight

January 26, 1999
University Of Illinois At Urbana-Champaign
One of life's simplest organisms -- a mud-dwelling photosynthetic bacterium -- is helping scientists unlock the complex structural makeup that occurs when proteins come together to perform important biological duties.

ANAHEIM, Calif. -- One of life's simplest organisms -- a mud-dwelling photosynthetic bacterium -- is helping scientists unlock the complex structural makeup that occurs when proteins come together to perform important biological duties.

Such knowledge, says Klaus Schulten of the University of Illinois, can shed light on what happens when proteins aggregate (combine and arrange) at the right time and when they do it at the wrong time, as is the case in diseases of the central nervous system such as Alzheimer's disease and bovine spongiform encephalopathy (Mad Cow Disease).

Speaking at the annual meeting of the American Association for the Advancement of Science, Schulten told how his theoretical biophysics group at the U. of I. Beckman Institute for Advanced Science and Technology combined X-ray crystallography and computational modeling to identify the structure of a protein called the two light-harvesting complex in the purple bacteria Rhodobacter sphaeroides. The protein is an aggregate of eight independent but identical units that form a highly symmetrical ring. A similar protein forms a ring of 16 units and surrounds the bacterium's photosynthetic reaction center.

The whole ensemble contains hundreds of chlorophylls as well as carotenoids, both of which are light-absorbing compounds that serve to harvest sunlight and funnel its energy to the centrally located reaction center.

Schulten, who holds the U. of I. Swanlund Chair in Physics, his Beckman Institute colleagues and collaborators of the Max Planck Institute for Biochemistry in Frankfort, Germany, first published their three-dimensional rendering in the May 1996 issue of the journal Structure. Subsequent accomplishments, including the creation of a colorful physical model of the photosynthetic center, based on the computer model, have been published in physics and biological journals and in the Proceedings of the National Academy of Sciences.

Using his hand-held, color-coded model, Schulten described how the components fit inside the ring: 24 chlorophylls (which make plants green); eight carotenoids (which make tomatoes red); and eight independent peptide units. They all collect and arrange into a protein membrane and feed energy into the bacterium's metabolism.

Having an accurate model of the structure, Schulten said, "is like having the Rosetta stone [a tablet of inscriptions found in 1799 that led to the deciphering of ancient Egyptian writing]; it provides us with the key for answering questions about the underlying physical components that go into the assembly and function of not only purple bacteria but also that of the light-harvesting complexes of more complex plants."

"This is a great example of how you can apply physics conceptually to biology to solve molecular mysteries," he said. "With this model, I can show how nature has molded a certain class of proteins to turn them into an apparatus that is uniquely effective in absorbing photons from the sun, conserving that energy and transporting it to certain points where other proteins take over the energy and use it. It provides us with a good example of the specialties within living systems. There are parts that can self-organize into very complex structures, and that ability is very distinct in organic systems."

His model is based on one of life's smallest systems. Purple bacteria live in the mud below surface plants. They are scavengers, feeding on bits, or photons, of sunlight that are not claimed by the plants. In fact, Schulten said, they "feed" on only two types of photons -- one with a wavelength of 500 nanometers and another of 800 nm -- which are absorbed, respectively, by the bacterium's carotenoids and chlorophylls. The carotenoids also play bodyguard to the chlorophylls and protect them from oxygen.

"Usually when you model something in a computer, you are not sure that what you do is reality and not just virtual reality," Schulten said. "But by having sufficient biological data, you can know that you are modeling correctly. In our case, the data without modeling could not be interpreted, but with the modeling we could complete a clear and correct structure of the light-harvesting protein."

Schulten's model shows "the beautiful capability of life to organize itself into components and do it spontaneously without something from the outside being there to place all the pieces together."

"It just happens spontaneously," he said. "But on the other side of the coin, something that works beautifully also can go wrong, and when it does you can have a lot of damage.

"Such unwanted assembly of protein can occur when the various components are not in complete order. They will still aggregate and form maybe beautiful structures, but they can be very detrimental. We know some of the resulting diseases very well," Schulten said. "One of them is Alzheimer's, in which certain proteins form plaques in the brain. Another is Mad Cow Disease, where a protein aggregates at the wrong time and causes a chain reaction of other proteins joining the aggregate."

Schulten told scientists at the AAAS that his model protein shows how "nature uses some very irregular forms to create something beautiful." But, he said: "I'm not saying that with this model we can cure Alzheimer's. There are many steps in understanding various biological systems. This model shows the structure of a protein in one of the purest, simplest systems. It has much to teach us about adhesion forces that govern self-assembly and how certain drugs may be targeted to interfere when assembly begins to occur at the wrong time."

Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.

Cite This Page:

University Of Illinois At Urbana-Champaign. "How Nature Harvests Sunlight." ScienceDaily. ScienceDaily, 26 January 1999. <www.sciencedaily.com/releases/1999/01/990126081107.htm>.
University Of Illinois At Urbana-Champaign. (1999, January 26). How Nature Harvests Sunlight. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/1999/01/990126081107.htm
University Of Illinois At Urbana-Champaign. "How Nature Harvests Sunlight." ScienceDaily. www.sciencedaily.com/releases/1999/01/990126081107.htm (accessed July 23, 2014).

Share This

More Matter & Energy News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Government Approves East Coast Oil Exploration

Government Approves East Coast Oil Exploration

AP (July 18, 2014) The Obama administration approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles. (July 18) Video provided by AP
Powered by NewsLook.com
Sunken German U-Boat Clearly Visible For First Time

Sunken German U-Boat Clearly Visible For First Time

Newsy (July 18, 2014) The wreckage of the German submarine U-166 has become clearly visible for the first time since it was discovered in 2001. Video provided by Newsy
Powered by NewsLook.com
Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Obama: U.S. Must Have "smartest Airports, Best Power Grid"

Reuters - US Online Video (July 17, 2014) President Barak Obama stopped by at a lunch counter in Delaware before making remarks about boosting the nation's infrastructure. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

Crude Oil Prices Bounce Back After Falling Below $100 a Barrel

TheStreet (July 16, 2014) Oil Futures are bouncing back after tumbling below $100 a barrel for the first time since May yesterday. Jeff Grossman is the president of BRG Brokerage and trades at the NYMEX. Grossman tells TheStreet the Middle East is always a concern for oil traders. Oil prices were pushed down in recent weeks on Libya increasing its production. Supply disruptions in Iraq fading also contributed to prices falling. News from China's economic front showing a growth for the second quarter also calmed fears on its slowdown. Jeff Grossman talks to TheStreet's Susannah Lee on this and more on the Energy Department's Energy Information Administration (EIA) report. Video provided by TheStreet
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.


Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News


Free Subscriptions

Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile

Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?

Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins