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  • THE ELECTRONIC ALADDIN NEWSLETTER NO. 36

    June 2004


    Wadsworth beamline now available to Users
    Scientists uncover possible templating process for biomineralization
    Synchrotron hosts US Particle Accelerator School
    SRC REU Program begins third summer
    Notes
     
     
    Wadsworth beamline now available to Users
     
    The new Wadsworth beamline at SRC has successfully completed the commissioning phase and proposals are being accepted for beamtime. The beamline utilizes the permanent magnet undulator source in long straight section two, port 041, of the Aladdin storage ring. It is the first SRC beamline without an entrance slit, meaning the Wadsworth performance is critically related to Aladdin undulator source characteristics. This novel optical design provides high flux density at the sample location. The Wadsworth beamline covers the energy range from 8 to 40 eV using three interchangeable gratings. The source size limited resolution is less than 5 meV throughout the range with a small final image of less than 0.5 X 0.5 mm.
     
    Initial testing indicates that the excellent source stability results in very reproducible spectra from the beamline. The system is capable of delivering world-class resolution photoemission experiments. Results from commissioning work done with the Scienta ARPES system are available at the SRC website, www.src.wisc.edu. Measurements of a gold Fermi edge resulted in a total width of 6.8 meV, one of the highest resolution PES spectra ever recorded with a synchrotron based light source.
     
     
    Scientists uncover possible templating process for biomineralization
    By Kendra Rand
     
    Biomineralization has intrigued scientists for years because of its possible applications to materials science­for example in simulating mollusks in their ability to create shells 3,000 times harder than the mineral alone. However, the templating process by which organisms form inorganic crystal structures has remained something of a mystery. In an article published in the March 12th issue of Science, a team of researchers from UW Madison, UC Berkeley, and the Istituto di Struttura della Materia in Rome announced how their work with a microbe found in the flooded Piquette mine in Tennyson, WI, indicates that polysaccharide polymers may contain the templation sites that direct crystal formation.
     
    Jillian Banfield, a geology professor, was intrigued when some recreational divers contacted her about a strange mineral deposit and the cloudy water above it in the flooded mine. SEM and TEM images of water samples revealed that the water was cloudy because it contained thousands of amorphous iron oxyhydroxide filaments, 20-200 nm wide and many micrometers long. Some of them appeared to be connected to microbes, evidence that the mineralized filaments were all connected to cells at one time, but when they became too long to be supported by the cell they broke off.  Subsequent analysis of the biofilm revealed similar structures, but the filaments in the biofilm had crystals in their cores with aspect ratios on the order of 1:1000. Discovering filaments 2-3 nm wide but thousands of nanometers long in the mine was particularly unusual, because this type of crystal usually forms only in environments with higher salinity.
     
    Because only the filaments in the biofilm, and not in the cloudy water, had akaganeite ( -FeOOH) crystals in their core (indicating crystal development over time) and those with the crystal cores also converted the remaining amorphous iron oxide into ferrihydrite, Banfield suspected that the polymer extruded by the cell was directing the crystallization process. In order to test this hypothesis and investigate the nature of the polymer, Banfield’s group joined forces with Gelsomina De Stasio and her group at the Synchrotron Radiation Center to use X-PEEM, an x-ray spectromicrosope. Unique in its ability to look at samples of various thicknesses over a range of energies with high sensitivity, X-PEEM could do what traditional instruments used in microchemical analysis, such as the SEM and TEM, could not do­it could look at the inorganic and organic parts of a filament at the same time.
     
    By using X-PEEM, De Stasio and her team found that some cells were extruding both mineralized and nonmineralized strands, leading them to hypothesize that the microbes extruded the polymer strands to induce mineralization. The group used iron spectromicroscopy to differentiate between the mineralized and nonmineralized strands and then correlated these results with carbon analysis results from x-ray absorption near-edge structure spectroscopy. They found that the spectrum of the nonmineralized polymers matched that of alginate­an acidic polysaccharide. Spectra from the mineralized filaments also indicated the presence of alginate, although they had an added C-O carbon peak which provides evidence that the COO- groups along the polysaccharides are the binding sites for iron oxyhydroxides, therefore the sites involved in the templation of akaganeite crystal cores.
     
    In the article the group also laid out a possible motive for the filament production and shedding. Mineralization occurs when the polysaccharide strands come in contact with oxidized iron. Both the process of iron oxidation and the precipitation of iron oxyhydroxide on the polymers release protons­decreasing the pH outside the cell membrane. This creates a proton gradient across the membrane, and therefore contributes to the proton motive force that generates metabolic energy. So, by extruding more of the polysaccharide when it is in a neutral or alkaline pH environment, the microbe can generate metabolic energy and then live on it. When the microbe can no longer support the growing mineralized filament, it sheds it. Over time the polysaccharide polymer directs the formation of the crystal at its core.
     
    Banfield, De Stasio, and their teams have made significant progress in uncovering­at the molecular level­the process through which biomineralization occurs. Identifying the polysaccharide chains as likely templation sites is an important step toward the ability to reproduce this mechanism in the lab and create stronger and better synthetic materials.
     
     
    Synchrotron hosts US Particle Accelerator School
     
    This summer UW-Madison and the Synchrotron Radiation Center (SRC) will host the semi-annual US Particle Accelerator School at the Madison Concourse Hotel from June 21 to July 2. The program will consist of courses offered for credit on a variety of topics relevant to accelerator studies.  SRC staff will be teaching a "Beam Instrumentation Laboratory at the SRC". This course will be a hands-on introduction to the experimental techniques used in measuring the properties of beams, accelerators, and related systems. Additional information is available at the USPAS web site uspas.fnal.gov.
     
     
    SRC REU Program begins third summer
     
    Four students from across the country arrived at SRC in early June for the third annual SRC Research Experience for Undergraduates program.  The students each work under a mentor with whom they develop and execute a research program.  Andrew Au is a junior at UW Madison majoring in chemical and biological engineering.  He is working with Franz Himpsel on molecular memory. Kathleen Barger is a senior at Western Washington University majoring in physics and minoring in math and astronomy. She is working with Ralf Wehlitz on molecular materials studies.  Maria Bravo is a senior at UW Madison majoring in genetics and French.  She is working with Gelsomina “pupa” De Stasio on prion diseases. Gabriel Pendas is a senior at Florida State University majoring in physics.  He is working with Joe Bisognano on accelerator physics.  During the nine weeks of the program, the students conduct research, attend seminars, and participate in activities with students from other REU programs at UW-Madison.
     
     
    Notes:
     
    The 37th SRC Users' Meeting will be held October 15-16 2004.
     
    Giorgio Margaritondo, former Associate Director of Research at SRC, was nominated Provost (Vice President for Academic Affairs) of the Ecole Polytechnique Federale-Lausanne, Switzerland.