SSRL Science Highlights Archive

Approximately 1,700 scientists visit SSRL annually to conduct experiments in broad disciplines including life sciences, materials, environmental science, and accelerator physics. Science highlights featured here and in our monthly newsletter, Headlines, increase the visibility of user science as well as the important contribution of SSRL in facilitating basic and applied scientific research. Many of these scientific highlights have been included in reports to funding agencies and have been picked up by other media. Users are strongly encouraged to contact us when exciting results are about to be published. We can work with users and the SLAC Office of Communication to develop the story and to communicate user research findings to a much broader audience. Visit SSRL Publications for a list of the hundreds of SSRL-related scientific papers published annually. Contact us to add your most recent publications to this collection.

SCIENCE HIGHLIGHT BANNER IMAGES

April 2004
Figure 1.

In ice, each water molecule is surrounding by 4 other molecules in a tetrahedral arrangement (left). The new result on liquid water shows that the molecules are connected only with 2 others. This implies that most molecules are arranged in strongly hydrogen bonded rings (middle) or chains (right) embedded in a disordered clusternetwork connected mainly by weak hydrogen bonds. The oxygen atoms are red and the hydrogen atoms grey in the water (H2O) molecules.

X-ray Absorption Spectroscopy, X-ray RAMAN spectroscopy
March 2004
John M. Zachara, Calvin C. Ainsworth, Gordon E. Brown, Jr., Jeffrey G. Catalano
Table 1.

Toxic and carcinogenic chromate (hexavalent chromium as CrO42-) has contaminated the groundwater in Hanford, Washington. At Hanford, hexavalent chromium was used in the industrial process to recover plutonium from irradiated nuclear fuels. The resulting high-level waste corroded its storage tanks and leaked into the desert subsoils. Plumes of contaminated groundwater reaching the Columbia River pose a risk to spawning salmon.

BL4-3, BL11-2
February 2004
P. Emma, K. Bane, M. Cornacchia, Z. Huang, H. Schlarb, D. Walz
Figure 1.

Computer simulations have shown that by using a cleverly placed piece of slotted foil, the Linac Coherent Light Source (LCLS) will be able to produce brilliant x-ray pulses that are extremely short, a few femtoseconds (a femtosecond is a quadrillionth of a second), in duration. This pulse length, which is a factor of more than 200 times shorter than the LCLS baseline design, will dramatically increase LCLS' x-ray time resolution, giving scientists the ability to study the movement of matter at atomic scales and accessing the structural changes occurring in the making or breaking of chemical bonds.

February 2004
David A. Bushnell, Kenneth D. Westover, Ralph E. Davis, Roger D. Kornberg
Figure 1.

Professor Roger D. Kornberg and his group in the Stanford University School of Medicine have devoted more than 20 years to the study of the process by which genetic information encoded in all living things by DNA is processed into a message (a process called transcription that produces messenger RNA) that then directs the synthesis of proteins. A breakthrough paper detailing the structures of the core RNA Polymerase II protein was published in Science in April 2000 and followed by two more papers in Science a year later.

Macromolecular Crystallography
BL9-2, BL11-1
January 2004
Kottayil I. Varughese, Zaverio M. Ruggeri, Reha Celikel
Figure 1.

When a blood vessel is cut, the body activates a repair mechanism that eventually seals the cut and prevents further blood loss. This life saving process becomes life threatening when clots form inside a functional blood vessel. Arrest of bleeding works through platelet adhesion and thrombin-induced fibrin formation at the site of injury. In order for the platelets to stick to the injured tissues and to each other, they need to be activated. Thrombin is an essential protease (a type of enzyme) that activates platelets and forms blood clots in response to vascular injury.

Macromolecular Crystallography
BL9-2
December 2003
Olivier Pelletier, Elena Pokidysheva, Linda S. Hirst, Nate Bouxsein, Youli Li, Cyrus R. Safinya
Figure 1.

With the completion of the Human Genome Project and the emerging proteomics era, the biosciences community is beginning the daunting task of understanding the structures and the structure-function relations of collections of interacting proteins. Cellular activity, which is tightly regulated, often results from protein-protein and protein-nucleic acid interactions, leading to the formation of large assemblies of biomolecules for distinct functions. Examples include DNA condensation during the cell cycle, and bundle and network formation of filamentous actin proteins in cell attachment, motility, and cytokinesis.

BL4-2, BL10-2
November 2003
Christopher C. Fuller, John R. Bargar, James A Davis
Figure 1.

A new technology that acts like a giant underground filter is successfully beginning to clean up the uranium contaminating an aquifer in a remote Utah canyon. Uranium contamination in groundwater is a serious problem because the toxic metal can travel long distances in underground aquifers, which are vital sources of fresh water for people, animals and agriculture. Recent research at SSRL showed that the filters-called PRBs (permeable reactive barrier) do intercept uranium, but in an unexpected way that has important implications for monitoring, costs, and future technology selection.

X-ray Absorption Spectroscopy
BL2-1, BL4-3, BL11-2
October 2003
Raquel L. Lieberman, Amy C. Rosenzweig, Timothy L. Stemmler
Figure 1.

A team headed by Timothy Stemmler of Wayne State University's School of Medicine and Amy Rosenzweig at Northwestern University, has isolated a new form of a bacterial enzyme that efficiently converts methane to methyl alcohol. This enzyme is isolated from methanotropic bacteria, which are found in soil, landfills, groundwater, seawater, hot springs and even the Antarctic. 

BL7-3
September 2003
B. L. Boyce, A. Mehta, J. O. Peters, R. O. Ritchie
Figure 1.

Aircraft turbine engines are prone to ingesting pebbles and other debris that can damage jet engine fan blades, dramatically reducing the longevity of the components - sometimes catastrophically. Failures associated with such "foreign object damage" cost the aerospace industry an estimated $4 billion a year. Studies at SSRL have helped show how and why fan blades - which normally experience significant stresses during flying - fatigue sooner than expected from foreign object damage.

X-ray diffraction
BL2-1
August 2003
Tuna

The presence of "methyl mercury" in fish is well-known, but until now the detailed chemical identity of the mercury has remained a mystery. In an x-ray absorption spectroscopy study published in the August 29 issue of Science (Science 301, 2003: 1203;Science now: Murky Picture on Fish Mercury), SSRL scientists report that the chemical form of mercury involves a sulfur atom (most likely in a so-called aliphatic form). The study presents significant new knowledge - because the toxic properties of mercury (or any element) are critically dependent upon its chemical form - and represents an important milestone in developing an understanding of how harmful mercury in fish might actually be. The study was carried out by SSRL staff scientists Ingrid Pickering and Graham George and postdoctoral fellow Hugh Harris using SSRL's structural molecular biology beam line 9-3. The very high flux, excellent beam stability and state-of-the-art detector technology allowed the team to measure samples of fish containing micromolar levels of mercury, much lower than had previously been possible.

X-ray Absorption Spectroscopy
BL9-3

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