The element chromium is found in the environment in two common forms: Cr(VI), which is easily absorbed by the human body, and Cr(III), which is not. The first of these in the form of chromates can have severe adverse effects on the human body, including cancerous tumor formation and gene damage. Normally Cr(VI) forms are not present in the approximately one billion tons of coal used annually for electricity generation in the U.S., however, a fraction of the Cr(III) in coal can become oxidized during coal combustion ending up as a Cr(VI) component in fly-ash, the major waste product from coal combustion.
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.
June 2011
X-ray Absorption Spectroscopy
BL4-3
June 2011
For decades, people have been using penicillium mold and molecules produced by soil bacteria as a means of fighting off harmful bacteria and treat infection. But resistance to these chemicals is now becoming commonplace. Today many infections are resistant to not only penicillin but also other β-lactam antibiotics, some of which are classified as “last line of defense” drugs for E. coli and Klebsiella pneumoniae.
Macromolecular Crystallography
BL12-2
June 2011
While nitrogen in the air is abundant, nitrogen as a form usable to life is limited. Bacteria associated with legumes use an enzyme called nitrogenase to combine N2 from the atmosphere with water to make ammonia, a form the plant can use. Since the early 1900s, industrial fertilizers have been made through a chemical method called the Haber-Bosch process. Because these reactions require high temperatures, pressures, and fossil fuels, scientists have renewed interest in learning how the bacteria perform their reactions.
Macromolecular Crystallography
BL12-2
June 2011
The selection and transcription of specific areas of DNA is a critical part of gene expression. Genes that code for proteins are transcribed into messenger RNAs by RNA polymerase II. This enzyme is recruited to parts of the genome by a number of transcription factors, which bind to particular DNA sequences like the TATA box. The transcription factor TFIIB brings the polymerase and the proper DNA sequences close together, and it helps define the direction of transcription.
Macromolecular Crystallography
BL12-2
June 2011
Viruses are dependent on the cellular machinery of their host cells, and often evolve tricks that allow them to sidestep the usual cellular protocols and more efficiently take advantage of cellular resources. Such is the case with a group of viruses that use an RNA sequence called an internal ribosome entry site (IRES), which allows their RNA to be efficiently translated into protein without the normal necessity of a more complicated cap structure. Certain IRESs do this by structurally mimicking a tRNA and mRNA in a way that can fit into the ribosome’s internal tRNA binding site.
Macromolecular Crystallography
BL12-2
May 2011
At times, different observational tools do not give the same answer when measuring the same thing. Such was the case when looking at the metalloenzyme transition state species Fe(IV)-O, important as an oxidant in a number of iron-containing enzymes. While x-ray absorption spectroscopic experiments determined the Fe-O bond length to be short (less than 1.7 Å), some results from crystallographic studies indicated that the bond length was longer (1.8-1.9 Å).
Macromolecular Crystallography
BL9-2
May 2011
To expand the use of hydrogen in mobile applications—such as hydrogen-powered buses and cars—researchers will need to design lightweight, compact means of storing it. One possible method is to store hydrogen inside carbon nanotubes. Theoretical predictions suggest that, through a mechanism that forms stable carbon-hydrogen bonds, it would be possible to store one hydrogen atom for every carbon atom inside single-walled carbon nanotubes.
BL13-2
April 2011
While much is known about how the acquired immune system recognizes and responds to pathogens, the innate immune system, which also fights off infections and disease, is much less well understood. The inflammatory responses of the innate immune system can be activated by toll-like receptors (TLRs), which often bind to elements from pathogens that have a regular repeat, such as double-stranded RNA.
Macromolecular Crystallography
BL9-2, BL11-1
April 2011
The nature of the pseudogap, which exists above the superconducting transition temperature (Tc) of high-Tc cuprate superconductors, is one of the most important unsolved problems in condensed matter physics. Many possible origins for the pseudogap, such as fluctuating superconductivity and competing order, have been proposed, however, since its discovery two decades ago, there has not been a conclusive experiment.
Angle-resolved photoelectron spectroscopy
BL5-4
March 2011
Organic or plastic solar cells have achieved efficiencies greater than 8%, close to the estimated 10% needed to make them economically viable. To close the gap, researchers need to improve control of the nanostructure of the active layer of these organic solar cells.
X-ray diffraction
BL11-3
Pages
