Corporate Banner
Satellite Banner
Crystallography
Scientific Community
 
Become a Member | Sign in
Home>News>This Article
  News
Return

A New Way of Looking at Photosynthesis

Published: Tuesday, June 12, 2012
Last Updated: Tuesday, June 12, 2012
Bookmark and Share
Future prospects for clean, green, renewable energy may hinge upon our ability to mimic and improve upon photosynthesis.

An artificial version of photosynthesis, for example, could use sunlight to produce liquid fuels from nothing more than carbon dioxide and water. First, however, scientists need a better understanding of how a large complex of proteins, called photosystem II, is able to split water molecules into oxygen, electrons and hydrogen ions (protons). A new road to reaching this understanding has now been opened by an international team of researchers, led by scientists at the U.S. Department of Energy (DOE)'s Lawrence Berkeley National Laboratory (Berkeley Lab) and SLAC National Accelerator Laboratory.

Using ultrafast, intensely bright pulses of X-rays from SLAC's Linac Coherent Light Source (LCLS), the research team produced the first ever images at room temperature of microcrystals of the photosystem II complex. Previous imaging studies, using X-rays generated via synchrotron radiation sources, required cryogenic freezing, which alters the samples. Also, to catalyze its reactions, photosystem II relies upon an enzyme that contains a manganese-calcium cluster that is highly sensitive to radiation. With the high-intensity femtosecond X-ray pulses of the LCLS, the research team was able to record intact images of these clusters before the radiation destroyed them.

"We have demonstrated that the ‘probe before destroy' strategy of the LCLS is successful even for the highly-sensitive oxygen bridged manganese-calcium cluster in photosystem II at room temperature," says Vittal Yachandra, a chemist with Berkeley Lab's Physical Biosciences Division. "This is an important step toward future studies for resolving the composition and atomic structure of the manganese-calcium cluster in the photosystem II complex during the critical formation of oxygen molecules."

For more than two billion years, nature has employed photosynthesis to oxidize water into molecular oxygen. Photosystem II, the only known biological system that can harness visible light for the photooxidation of water, produces most of the oxygen in Earth's atmosphere through a five-step catalytic cycle (S0-to-S4 oxidation states). Light-harvesting proteins in the complex capture solar photons that energize the manganese-calcium cluster and drive a series of oxidations and proton transfers that in the final S4 state forms the bond between oxygen atoms that yields molecular oxygen.
Scientific teams in the past, including several led by Yachandra and Yano, have shed much light on the S0 through S3 oxidation states of the manganese-calcium cluster, which remain stable for several seconds. However, the S4 state is highly reactive and has not yet been fully characterized in experiments.

"Capturing the S4 state in a time-resolved manner will be essential for understanding the water-oxidation mechanism,"  Yano says. "While X-ray diffraction is clearly the technique of choice for such detailed structural studies, the inherent radiation sensitivity of the manganese-calcium cluster poses a major challenge for protein crystallography on synchrotron radiation sources."

SLAC's LCLS is an X-ray laser powered by a two-mile-long linear accelerator (or linac) that generates pulses of X-ray light on a femtosecond timescale. These pulses are more than a billion times brighter than those from the most powerful synchrotrons. Yachandra, Yano and their colleagues suspended photosystem II microcrystals in a liquid that was jet-streamed into the path of the pulsed light. The diffraction of LCLS X-rays passing through the photosystem II microcrystals created patterns that computers reconstructed into images of the complex's composition and atomic structure at a resolution of 6.5 angstroms - one ten-billionth of a meter or about the diameter of a hydrogen atom.

"We hope that with improved samples, in the future we will be able to get to a higher resolution - perhaps 3 angstroms or better," says Jan Kern, a research scientist at Berkeley Lab and SLAC who was the lead author on the PNAS paper.

Photosystem II microcrystals (approximately 10 micrometers in diameter)were used as a matter of efficiency. Molecular reconstruction through X-ray diffraction requires the examination of literally millions of crystals, since each shot from the LCLS destroys the specimen.

"Because it takes months to grow sufficient quantities of the photosystem II complex in bacterial culture, the use of microcrystals made the most efficient use of time and materials," says Kern. "Also, microcrystals were much easier to direct toward the LCLS X-ray beam using the liquid-stream sample delivery system developed by our collaborators at SLAC."

Paul Adams and Nicholas Sauter, also with Berkeley Lab's Physical Biosciences Division and also co-authors of the PNAS paper, led the data analysis in this study, writing new software to manage the computations.

"Doing this study was a monumental achievement that required a large team to make it happen," Sauter says. "We injected crystal samples into the beam at a rate of 120 per second, and after a week we had 63 Terabytes of data from which we selected the best 7,000 diffraction images to reconstruct photosystem II's molecular structure."

Further studies at the LCLS by the research team are already underway using both X-ray diffraction and spectroscopy techniques to investigate the intermediate reaction states formed in the photosystem II complex as it undergoes photooxidation.

"We hope to learn from nature's design principles and apply that knowledge to the design and development of artificial photosynthetic systems," Yano says.


Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,400+ scientific posters on ePosters
  • More than 3,700+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Structure of Key Pain-Related Protein Unveiled
In a technical tour de force, scientists have determined, at near-atomic resolution, the structure of a protein that plays a central role in the perception of pain and heat.
Friday, December 06, 2013
Preventing Cells from Getting the Kinks Out of DNA
Discovery could pave the way for new research into how to re-design these drugs to make them more effective poisons for cancer cells and harmful bacteria.
Monday, May 24, 2010
University of California Demonstrates Wyatt’s Dynapro is Effective for Protein Unfolding
The aim of this experiment was to follow the unfolding process using Dynamic Light Scattering.
Friday, July 21, 2006
Scientific News
TOPLESS Plants Provide Clues to Human Molecular Interactions
Scientists at Van Andel Research Institute have revealed an important molecular mechanism in plants that has significant similarities to certain signaling mechanisms in humans, which are closely linked to early embryonic development and to diseases such as cancer.
Advancing Cancer Drug Design with Image of Key Protein
Scientists have pioneered the use of a high-powered imaging technique to picture in exquisite detail one of the central proteins of life – a cellular recycling unit with a role in many diseases.
Mould Unlocks New Route to Biofuels
Scientists at The University of Manchester have made an important discovery that forms the basis for the development of new applications in biofuels and the sustainable manufacturing of chemicals.
'Invisible' Protein Structure Explains the Power of Enzymes
A research group at Umeå University in Sweden has managed to capture and describe a protein structure that, until now, has been impossible to study.
Unraveling the Elusive Structure of HIV Protein
Snapshots of HIV virus’ proteins may help design new ways to fight the disease.
Blueprinting Cell Membrane Proteins
Recent breakthrough will make the blueprinting process faster, easier and cheaper, and should have major implications in the field of drug discovery and development.
Bacteria Use Chemical Harpoons to Hold on Their Hosts
Researchers reveal how a common disease causing bacteria latches on to the body during an infection.
Solving Streptide from Structure to Biosynthesis
Researchers reveal new information about how bacteria communicate via the protein, streptide.
Near-Atomic Resolution of Protein Structure Holds Promise for Drug Discovery
A new study shows that it is possible to use an imaging technique called cryo-electron microscopy to view the architecture of a metabolic enzyme bound to a drug that blocks its activity.
X-ray Study May Aid in Designing Better Blood Pressure Drugs
New atomic-scale details could help create more effective medications with fewer side effects.
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,400+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,700+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FREE!