Research Highlights and New Publications

The reactions that convert light to chemical energy happen in a millionth of a millionth of a second, which makes experimental observation extremely challenging. A premier ultrafast laser spectroscopic detection system established at the Biodesign Institute, with the sponsorship of the National Science Foundation, acts like a high-speed motion picture camera. It splits the light spectrum into infinitesimally discrete slivers, allowing the group to capture vast numbers of ultrafast frames from the components of these exceedingly rapid reactions. These frames are then mathematically assembled, allowing the group to make a figurative "movie" of the energy transfer events of photosynthesis.

May 13, 2009

Pliable proteins keep photosynthesis on the light path
Su Lin, Neal Woodbury, Aaron Tufts and James P. Allen publish in the Proceedings of the National Academy of Sciences...

Photosynthesis is a remarkable biological process that supports life on earth. Plants and photosynthetic microbes do so by harvesting light to produce their food, and in the process, also provide vital oxygen for animals and people. Now, a large, international collaboration between Arizona State University, the University of California San Diego and the University of British Columbia, has come up with a surprising twist to photosynthesis by swapping a key metal necessary for turning sunlight into chemical energy.

The team, which includes: ASU scientists Su Lin, Neal Woodbury, Aaron Tufts and James P. Allen; UBC colleagues J. Thomas Beatty, Paul R. Jaschke, Federico I. Rosell and A. Grant Mauk; Mark Paddock, UCSD; Haiyu Wang, Jilin University, China, described their findings in the May 11 early online edition of the Proceedings of the National Academy of Sciences (http://www.pnas.org/content/early/2009/05/12/0812719106.abstract).

The results may enable researchers to explore a deeper understanding of the structure, function, and evolution of photosynthesis reaction centers in photosystems I and II. Of particular interest, are studies that focus on the interaction between chlorophylls and protein, which differs in naturally occurring reaction center variants. The team may also conduct future experiments to understand the metal substitution limitations of the reaction center and track the protein movements that may be occurring in the reaction center that helps to optimize photosynthesis.

Their results may have long-term practical applications for the development of next-generation solar cells, which could, through biomimicry of photosynthesis, greatly boost the energy efficiency compared with current technology. The robustness of the natural system may offer some useful lessons for engineers trying to improve on current technologies, and bring the costs of solar panels down to the average consumer.

Woodbury has proposed that there might be a way to increase the flexibility of the system used in organic solar cells by incorporating solvents that move on a variety of time scales that could "tune" the molecules to work in a wider variety of conditions.

"Electron transfer in the Rhodobacter sphaeroides reaction center assembled with zinc bacteriochlorophyll", Su Lin, Paul R. Jaschke, Haiyu Wanga, Mark Paddock, Aaron Tufts, James P. Allen, Federico I. Rosell, A. Grant Mauke, Neal W. Woodbury, J. Thomas Beatty, PNAS published online before print May 13, 2009, doi:10.1073/pnas.0812719106.

Link to the Abstract

Full story in EurekAlert

April 20, 2009

Unlikely life thriving at Antarctica's Blood Falls
Anbar group analyzes samples...

An unmapped reservoir of briny liquid chemically similar to sea water, but hidden under an inland Antarctic glacier, appears to support microbial life in a cold, dark, oxygen-poor environment- a most unexpected setting to be teeming with life.

The McMurdo Dry Valleys of Antarctica are devoid of animals and complex plants and scientists consider them to be one of the Earth's most extreme deserts. The Valleys receive, on average, only 10 cm (3.93 inches) of snow each year. Despite the lack of precipitation, during the Antarctic summer, temperatures rise just enough for glaciers protruding into the valleys to begin melting. The meltwater forms streams that enter lakes covered by ice that is two-to-three-stories thick.

Even less forgiving are the conditions found below the Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet in the otherwise ice-free Dry Valleys. The lack of light beneath the glacier makes the process of photosynthesis improbable, causing researchers to wonder how organisms found below the glacier could survive.

The research, which appears in the April 17 issue of Science, suggests that over the past 1.5 million years the microbes adapted to manipulate sulfur and iron compounds to survive. In place of photosynthesis, the microbes converted Fe(III) to Fe(II) to create food and energy.

The study was led by Jill Mikucki, a National Science Foundation-funded researcher at Dartmouth College. Mikucki and a team of researchers based their analysis on samples taken at the ominously, but aptly named Blood Falls, a water-fall-like feature at the edge of the glacier that flows irregularly, but often has a strikingly bright red appearance in stark contrast to the icy background.

The key piece of data supporting the hypothesis that the microbes were in fact surviving by turning Fe(III) to Fe(II) came from samples analyzed by Ariel Anbar, one of the authors of the study and an associate professor at Arizona State University, and researchers in his group, using instruments in the W. M. Keck Laboratory for Environmental Biogeochemistry at ASU.

"We found that the isotopes of Fe(II) in the brines are shifted in a way that is consistent with this microbial process,''said Anbar, who holds joint appointments in the School of Earth and Space Exploration and the Department of Chemistry and Biochemistry in the College of Liberal Arts and Sciences.

Even the earliest explorers noted the massive red stain at the snout of the glacier and speculated as to what may have caused it. Some guessed that red alga was responsible for the bright color.''In fact, the red color is a result of all that Fe(II) produced by bacteria,''said Anbar.''When the Fe(II)-rich water reaches the surface, the Fe(II) reacts with oxygen in the air to make Fe(III) compounds that are sort of like rust. That's the source of the red color.''

The microbes are remarkably similar in nature to species found in marine environments, leading to the conclusion that the populations under the glacier are the remnants of a larger population of microbes that once occupied a fjord or sea that received sunlight. Many of these marine lineages likely declined, while others adapted to the changing conditions when the Taylor Glacier advanced, sealing off the system under a thick ice cap.

In the paper, however, Mikucki and her colleagues argue that the creatures that survive under the Taylor Glacier are both far more exotic and far more adaptable than the early explorers thought.

Because the outflow from the glacier follows no clear pattern, it took a number of years to obtain the samples needed to conduct an analysis. Finally Mikucki obtained a sample of an extremely salty and clear liquid for analysis.

"When I started running the chemical analysis on it, there was no oxygen,''she said.''That was when this got really interesting; it was a real ‘eureka' moment.''

Further genetic analysis suggests that of the relatively small numbers of microorganisms found in the brine,''the majority of these organisms are from marine lineages,''she said.

In other words, microorganisms more similar to those found in an ocean than on land, but capable of surviving without the food and light sources available in the open ocean.

"The salts associated with these features are marine salts, and given the history of marine water in the dry valleys, it made sense that subglacial microbial communities might retain some of their marine heritage,''she added.

This led to the conclusion that the ancestors of the microbes beneath the Taylor Glacier probably lived in the ocean many millions of years ago. When the floor of the Valleys arose more than 1.5 million years ago, a pool of seawater from the fjord that penetrated the area was trapped. The pool was eventually capped by the flow of the glacier.

The briny pond, whatever its size''is a unique sort of time capsule from a period in Earth's history,''Mikucki said.''I don't know of another environment quite like this on Earth.''

Life below the Taylor Glacier may help scientist address questions about life on''Snowball Earth”, the period of geological time when large ice sheets covered the Earth's surface. But it's also a rich laboratory for studying life in other hostile environments, including the subglacial lakes of Antarctica and perhaps even on other icy planets in the solar system such as below the Martian ice caps or in the ice-covered oceans of Jupiter's moon Europa.  

ASU MEDIA CONTACT: Nikki Staab, nstaab@asu.edu 480-727-9329
NSF MEDIA CONTACT: Peter West, pwest@nsf.gov 703-292-7761  

"A Contemporary Microbially Maintained Subglacial Ferrous "Ocean"", Jill A. Mikucki, Ann Pearson,David T. Johnston, Alexandra V. Turchyn, James Farquhar, Daniel P. Schrag, Ariel D. Anbar, John C. Priscu, Peter A. Lee, Science 17 April 2009: Vol. 324. no. 5925, pp. 397 - 400 DOI: 10.1126/science.1167350

Link to the Abstract

April 2, 2009

Scanning tunneling microscopy (STM) helps with DNA sequencing...Stuart Lindsay, Otto Sankey and colleagues have recently published in Nature Nanotechnology...

Hydrogen bonding has a ubiquitous role in electron transport and in molecular recognition, with DNA base pairing being the best-known example. Scanning tunnelling microscope images and measurements of the decay of tunnel current as a molecular junction is pulled apart by the scanning tunnelling microscope tip are sensitive to hydrogen-bonded interactions. Here, Lindsay and coworkers show that these tunnel-decay signals can be used to measure the strength of hydrogen bonding in DNA base pairs. Junctions that are held together by three hydrogen bonds per base pair (for example, guanine-cytosine interactions) are stiffer than junctions held together by two hydrogen bonds per base pair (for example, adenine-thymine interactions). Similar, but less pronounced effects are observed on the approach of the tunnelling probe, implying that attractive forces that depend on hydrogen bonds also have a role in determining the rise of current. These effects provide new mechanisms for making sensors that transduce a molecular recognition event into an electronic signal.

"Tunnelling readout of hydrogen-bonding-based recognition", Shuai Chang, Jin He, Ashley Kibel, Myeong Lee, Otto Sankey, Peiming Zhang& Stuart Lindsay, Nature Nanotechnology. Published online: 22 March 2009 | doi:10.1038/nnano.2009.48

Link to the Abstract
Full story on biodesign website

Mar 17, 2009

CREDIT: K. SUTLIFF/SCIENCE

Allen and Williams' research highlighted in Science...

ORIGINS: On the Origin of Photosynthesis
Mitch Leslie
Science March 2009: Vol. 323. no. 5919, pp. 1286 - 1287

Where would we be without photosynthesis? In the third essay in Science's series in honor of the Year of Darwin, Mitch Leslie details researchers' efforts to piece together how and when organisms first began to harness light's energy.

An excerpt from the article follows...

Biochemists James Allen and JoAnn Williams of Arizona State University, Tempe, and colleagues are working out how a bacterial reaction center could have evolved photosystem II's appetite for electrons. Taking a hands-on approach, they have been tinkering with the reaction center of the purple bacterium Rhodobacter sphaeroides to determine if they can make it more like photosystem II. First they targeted bacterio- chlorophyll, the bacterial version of chlorophyll that's at the core of the reaction center, and altered the number of hydrogen bonds. Adding hydrogen bonds hiked the molecule's greed for electrons, they found. The water-cleaving portion of photosystem II sports four manganese atoms that become oxidized, or lose electrons. So the team equipped the bacterial reaction center with one atom of the metal. In this modified version, the added manganese also underwent oxidation, the researchers reported in 2005. James Allen says that their creations aren't powerful enough to split water. But eventually, they hope to engineer a reaction center that can oxidize less possessive molecules, such as hydrogen peroxide, that would have been present on the early Earth. Even if the researchers never replicate photosystem II, "if we define the intermediate stages, we've accomplished a lot," he says.  

   Link to the full article

Mar 3 , 2009

Gust, Moore and Moore publish in the Chem. Soc. Rev.'s 2009 Renewable Energy issue, reviewing the latest developments in renewable energy research

Biology and technology for photochemical fuel production Michael Hambourger, Gary F. Moore, David M. Kramer, Devens Gust, Ana L. Moore and Thomas A. Moore Sunlight is the ultimate energy source for the vast majority of life on Earth, and organisms have evolved elegant machinery for energy capture and utilization. Solar energy, whether converted to wind, rain, biomass or fossil fuels, is also the primary energy source for human-engineered energy transduction systems. This tutorial review draws parallels between biological and technological energy systems. Aspects of biology that might be advantageously incorporated into emerging technologies are highlighted, as well as ways in which technology might improve upon the principles found in biological systems. Emphasis is placed upon artificial photosynthesis, as well as the use of protonmotive force in biology.

"Biology and technology for photochemical fuel production", Michael Hambourger, Gary F. Moore, David M. Kramer, Devens Gust, Ana L. Moore and Thomas A. Moore, Chem. Soc. Rev., 2009, 38, 25 - 35, DOI: 10.1039/b800582f

Link to Abstract

"Engineered and Artificial Photosynthesis: Human Ingenuity Enters the Game", Devens Gust, David Kramer, Ana Moore , Thomas A. Moore, and Wim Vermaas , MRS BULLETIN, VOLUME 33 • APRIL 2008, p383.

Link to the full article

Feb 17 , 2009

Buseck and Adachi publish in a special issue of Elements on nanoparticles in the environment ...

The most continuous and intimate contact the average person has with nanoparticles is almost surely through the air, which is replete with them. Nanoparticles are being generated continuously and in large numbers by vehicles and industries in urban areas and by vegetation and sea spray in rural areas. Volcanoes are sporadic sources of huge numbers. Nanoparticles have large surface area to volume ratios and react rapidly in the atmosphere, commonly growing into particles large enough to interact with radiation and to have serious consequences for visibility and local, regional, and global climate. They also have potentially significant health effects.

The figure on the right shows nanoparticles from biomass burning. Also a photograph of a region of biomass burning, taken near Mexico City (top left). Gases emitted from the fires cooled rapidly and condensed or accumulated as nanoparticles. A low- magnification transmission electron micrograph is shown (bottom left) of biomass-burning particles collected from an airplane and deposited on a substrate of lacey carbon (fibers). This is enlarged to the right and shows nanoparticles trapped within a larger organic particle and therefore observable (red arrows). Other aerosol particles are indicated by white arrows. The compositions were determined using energy dispersive X-ray spectrometry. The sample was collected from aircraft during an international atmospheric campaign called MILAGRO, sponsored by NSF, NASA, DOE, and various other national and international agencies as part of a program to study emissions from tropical megacities. The photo was taken by Kouji Adachi.

"Nanoparticles in the atmosphere", P.R. Buseck and K. Adachi,Elements 4, 389-394, 2008.

Link to Abstract

Jan 31, 2009

Byrne and Angell publish article on biomolecules "out of water"...

In a contribution currently in press Chemical Communications, Nolene Byrne and Austen Angell give another example how use of protic ionic liquid solvents for biomolecule studies can produce interesting phenomena. Although there is only one molecule of water for every two ions present in these solvents, the dissolved proteins behave in many cases as if they are in normal aqueous buffer - except that they seem to be more stable against aggregation. In the present communication these authors show that, also as in aqueous solutions, change of solution conditions to more acidic states can lead to fibril formation. These are the same sort of amyloid fibril that cause Parkinson's and Jacob Kreutz "folding" diseases. However, now, with the right choice of ionic liquids, the fibrils can be readily redissolved. The authors even show that in some cases, most of the original bioactivity can be restored. 

"Formation and dissolution of hen egg white lysozyme amyloid fibrils in protic ionic liquids", Nolene Byrne and C. Austen Angell, Chem. Commun., 2009, 1046

Link to abstract

Jan 6, 2009

Movie showing the 3D architecture of nanotubes formed with 5 nm and 10 nm AuNPs (gold particles). Play Video

Hao Yan and Yan Liu's group publish in this week's Science on the self-assembly of DNA tubules...

DNA tubes are known to form through either self-association of multi-helix DNA bundle structures or closing up of 2D DNA tile lattices. By the attachment of single-stranded DNA to gold nanoparticles, nanotubes of various 3D architectures can form, ranging in shape from stacked rings to single spirals, double spirals, and nested spirals. The nanoparticles are active elements that control the preference for specific tube conformations through size-dependent steric repulsion effects. For example, one can control the tube assembly to favor stacked-ring structures using 10-nanometer gold nanoparticles. Electron tomography reveals a left-handed chirality in the spiral tubes, double-wall tube features, and conformational transitions between tubes.

The future of the nanotechnology field depends on our ability to reliably and reproducibly assemble nanoparticles into 3D structures we can use to develop new technologies. According to Hao Yan and Yan Liu at Arizona State University, the greatest challenges in this burgeoning field include control over nanoscale 3D structure and imaging these tiny materials.

"Control of Self-Assembly of DNA Tubules Through Integration of Gold Nanoparticles", Jaswinder Sharma, Rahul Chhabra, Anchi Cheng, Jonathan Brownell, Yan Liu, and Hao Yan Science 2 January 2009: 112-116.

Link to Abstract