Subscribe free to our newsletters via your
. Space Travel News .




FARM NEWS
A New Way of Looking at Photosystem II
by Lynn Yarris for Berkeley News
Berkeley CA (SPX) Jun 14, 2012


This electron density map of the manganese-calcium cluster in the photosystem II complex showed that the cluster was not dislocated by the LCLS X-ray beams before image data was acquired, proof that the probe-before-destroy approach is feasible for this system at the LCLS.

Future prospects for clean, green, renewable energy may hinge upon our ability to mimic and improve upon photosynthesis - the process by which green plants, algae and some bacteria convert solar energy into electrochemical energy. 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."

Yachandra is one of the corresponding authors of a paper describing this work in the Proceedings of the National Academy of Sciences (PNAS) titled "Room temperature femtosecond X-ray diffraction of photosystem II microcrystals. The other corresponding authors are Junko Yano, also a chemist with Berkeley Lab's Physical Biosciences Division, and Uwe Bergmann of SLAC.

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.

Other co-authors of the PNAS paper on this research were Roberto Alonso-Mori, Julia Hellmich, Rosalie Tran, Johan Hattne, Hartawan Laksmono, Carina Glockner, Nathaniel Echols, Raymond Sierra, Jonas Sellberg, Benedikt Lassalle-Kaiser, Richard Gildea, Pieter Glatzel, Ralf Grosse-Kunstleve, Matthew Latimer, Trevor McQueen, Dorte DiFiore, Alan Fry, Marc Messerschmidt, Alan Miahnahri, Donald Schafer, Marvin Seibert, Dimosthenis Sokaras, Tsu-Chien Weng, Petrus Zwart, William White, Michael Bogan, Sebastien Boutet, Garth Williams, Johannes Messinger and Athina Zouni. In addition to Berkeley Lab and SLAC, other institutions represented in this study were Stanford University, Germany's Technical University Berlin, the European Synchrotron Radiation Facility in France, and Umea University in Sweden.

.


Related Links
SLAC's Linac Coherent Light Source
Lawrence Berkeley National Laboratory
Farming Today - Suppliers and Technology






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





FARM NEWS
Niger farmland threatened by locusts: official
Niamey (AFP) June 13, 2012
Large swathes of farmland are threatened by locusts in Niger even as the drought-prone African nation is grappling with a severe food crisis, a pest-control official said Wednesday. "Unless swarms are destroyed very early, locusts will reproduce and reach the cropland," Yahaya Garba, director of the CNLA agency in charge of pest-control, said in the latest bulletin of the UN Office for the C ... read more


FARM NEWS
NASA's NuSTAR Mission Lifts Off

Orbital Launches Company-Built NuSTAR Satellite Aboard Pegasus Rocket for NASA

NuSTAR Arrives at Island Launch Site

Another Ariane 5 begins its initial build-up at the Spaceport

FARM NEWS
Impact atlas catalogs over 635,000 Martian craters

e2v imaging sensors launched into space on NASA mission to Mars

NASA Mars Rover Team Aims for Landing Closer to Prime Science Site

NASA's Mars rover zeroes in on August landing

FARM NEWS
Nanoparticles found in moon glass bubbles explain weird lunar soil behaviour

UA Lunar-Mining Team Wins National Contest

NASA Lunar Spacecraft Complete Prime Mission Ahead of Schedule

NASA Offers Guidelines To Protect Historic Sites On The Moon

FARM NEWS
It's a Sim: Out in Deep Space, New Horizons Practices the 2015 Pluto Encounter

Beyond Pluto And Exploring the Kuiper Belt

Uranus auroras glimpsed from Earth

Herschel images extrasolar analogue of the Kuiper Belt

FARM NEWS
Extremely little telescope discovers pair of odd planets

Alien Earths Could Form Earlier than Expected

Planets can form around different types of stars

Small Planets Don't Need 'Heavy Metal' Stars to Form

FARM NEWS
Secret U.S. space plane prepares to land

NASA Surpasses Test Facility Record With Long-Duration J-2X Powerpack Test

NASA Begins Development of Space Launch System Flight Software

Dream Chaser Flight Vehicle Scales Rocky Mountain Summits

FARM NEWS
China's manned spacecraft in final preparations for mid-June launch

Tiangong's Big Tasks

Media Tonedown for Tiangong

Shenzhou-9 full-system drill a success

FARM NEWS
'Unusually large' asteroid to race by Earth

Dawn Mission Video Shows Vesta's Coat of Many Colors

Dawn deep in the asteroid belt orbiting Vesta

UT's Josh Emery Uncovers Clues About Asteroid That Will Pass Near Earth




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement