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.


August 2003

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
August 2003
Sompop Bencharit, Matthew R. RedinboSSRL has played an important role in characterizing a family of enzymes that detoxify heroin and cocaine, and
Figure 1.

SSRL has played an important role in characterizing a family of enzymes that detoxify heroin and cocaine, and have the potential to metabolically eliminate the nerve poisons sarin, soman, and tabun, which have claimed thousands of lives. Using x-ray crystallographic data, the Redinbo group at the University of North Carolina at Chapel Hill has uncovered the specific and general ways the carboxylesterase enzymes bind to those dangerous substances. 

Macromolecular Crystallography
BL7-1, BL9-1, BL9-2
July 2003
Irimpan I. Mathews, Ashley M. Deacon, Jaume M. Canaves, Daniel McMullan, Scott A. Lesley, Sanjay Agarwalla, Peter Kuhn
Figure 1.

SSRL scientists have determined key binding sites in an enzyme family common to Anthrax, Botulism, Syphilis, Diarrhea and Lyme's disease. The protein x-ray crystallography data have already enabled the scientists to create a computer model of a molecule that could inhibit the enzyme's activity, which is essential for many single-celled organisms to replicate. 

Macromolecular Crystallography
June 2003
Figure 1.

Electron transfer, the process of moving an electron from one place to another, is vital to almost all chemical systems. It is a fundamental process in organic synthesis, in catalysis, and in the biochemistry of all living organisms. In biological systems, transition metal centers (such as iron and copper) often play the central role in an electron transfer protein, shuttling electrons within or between proteins.

May 2003
Colleen M. Hansel, Bruce W. Wielinga, Scott Fendorf
Figure 1.

Industrial activities have led to widespread chromium (Cr) contamination in the environment. Although Cr is an essential element for humans, the hexavalent form is toxic, mutagenic and carcinogenic. Consequently, the presence of Cr in the environment poses a serious threat to human and animal welfare. However, the toxicity of Cr is a function of oxidation state. For example, hexavalent Cr has a high solubility in soils and groundwater and, as a consequence, tends to be mobile in the environment.

X-ray Absorption Spectroscopy
BL4-1, BL4-3
April 2003
Andrey S. Krasilnikov, Xiaojing Yang, Tao Pan, Alfonso Mondragón
Figure 1.

One of the primary ways people find structure and coherence in the world is to identify fundamental characteristics common within and between apparently different classes - plants, humans, atoms, stars, etc. In the case of diverse biological life we know that RNA and/or DNA are common to them all. Thus, a deeper understanding of the architecture and interactions of RNA and DNA will lead to a greater understanding of the commonalities underlying all biological life.

Macromolecular Crystallography
March 2003
Rick Russell, Ian S. Millett, Sebastian Doniach, Daniel Herschlag
Figure 1

Determining how RNA (ribonucleic acid) folds, or "ravels", may offer a key to un-raveling how and why anomalies occur in the human genome. RNA is now known to play a pivotal role in gene silencing, gene shuffling, protein regulation and disease. However in contrast to proteins, very little is known about how RNA takes its three-dimensional shape and under certain circumstances works as an enzyme. Getting a good look at RNA in the process of folding from its initial 1-D "ribbon" state, into a 3-D "knot" (the form in which RNA is biologically functional) would be very valuable information

Biological Small-angle X-ray Scattering (BioSAXS)
February 2003
John A Pople, SSRL, Willy Wiyatno
Figure 1

Much of our manufactured environment - many metals, plastics, glasses, ceramics, fiberglass and papers - consists of extrusion-molded products. To minimize waste, extrusion-molding plants must balance quality of product, speed of process and cost of production (primarily electricity) for each particular material. They need to know how fast each material can be processed at what energy cost while maintaining the quality of the finished bulk material. Fundamental changes in the macromolecular arrangement of materials occur at critical deformation rates.

Materials Small-angle X-ray Scattering (SAXS)
January 2003
N. M. Markovic, LBNL, C. A. Lucas, University of Liverpool
Figure 1

Electrocatalysis is the science of modifying the overall rates of electrochemical reactions so that selectivity, yield and efficiency are maximized. Studies in electrocatalysis have resulted in tools such as highly selective multicomponent gas mixture sensors and better electrocatalysts for the fuel cells. Markovic and Lucas have been very active in studying the mechanisms by which these catalysts operate and developing in-situ surface x-ray scattering (SXS) techniques for their studies. 

X-ray scattering
December 2002
Katharina Lüning, Sean Brennan, Piero Pianetta

Increasing the speed and complexity of semiconductor integrated circuits requires advanced processes that put extreme constraints on the level of metal contamination allowed on the surfaces of silicon wafers. Such contamination degrades for example the performance of the ultra thin SiO2 gate dielectrics (< 4nm) that form the heart of the individual transistors. Ultimately, reliability and yield are reduced to levels that must be improved before new processes can be put into production. Much of this metal contamination occurs during the wet chemical etching and rinsing steps required for the manufacture of integrated circuits and industry is actively developing new processes that have already brought the metal contamination to levels beyond the detection capabilities of conventional analytical techniques.



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