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.

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
BL9-1
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)
BL4-2
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)
BL1-4
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
BL7-2
December 2002
Katharina Lüning, Sean Brennan, Piero Pianetta
Baur

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.

BL6-2
November 2002
Hope Ishii, Sean Brennan, Arthur Bienenstock
Figure 1.

Attempting to determine and describe the atomic arrangements in an amorphous material is a daunting prospect. A considerable advance has been made in the anomalous X-ray scattering approach to determining these arrangements in materials containing two atomic species.

X-ray scattering, X-ray Absorption Spectroscopy
BL10-2
October 2002
M. Greven, L. Zhou, S. Larochelle
Figure 1.

Many condensed matter systems can be described as large collections of microscopic entities, each of which can be in one of two possible states. For example, in many anisotropic magnets spins can point in one of two directions along a unique crystalline axis.  In a liquid-gas phase transition, molecules will be in either the gas or liquid phase.  When the microscopic entities interact, they may exhibit collective long-range order.  A collection of two-state particles with near-neigh bor interactions is known as an Ising system.  This simple system is very important because the behavior that an Ising system displays as it undergoes a transition to long-range order has universal features that are independent of the details of the two-state particles or their interaction.

BL7-2
September 2002
Douglas C. Rees, California Institute of Technology
Figure 1.

The Research group of Douglas Rees at the California Institute of Technology collected X-ray crystallographic data to a resolution of 1.16 Å at SSRL Beam Line 9-2 using the new Quantum-315 CCD detector from crystals of Nitrogenase MoFe-Protein, an extremely efficient enzyme found in bacteria that catalyzes the production of ammonia from dinitrogen. Bacteria produce about half of the world’s bio-nitrogen available for agriculture, the rest comes from nitrogenous fertilizer produced chemically at extreme temperature and pressure, consuming about 1% of the world's total annual energy supply. 

Macromolecular Crystallography
BL9-2
August 2002
Kaspar P. Locher, Allen T. Lee, Douglas C. Rees, Caltech
Figure 1.

Transport proteins, embedded in lipid membranes, facilitate the import of nutrients into cells or the release of toxic products into the surrounding medium. The largest and arguably the most important family of membrane transport proteins are the ABC transporters. They are ubiquitous in biology and power the translocation of substrates across the membrane, often against a concentration gradient, by hydrolyzing ATP (Higgins, 1992). 

Macromolecular Crystallography
BL9-2

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