APS advances frontiers in many fields (continued)

Iron at the core
University of Chicago researchers using the APS diamond anvil cell found experimental evidence that the Earth’s inner core consists largely of two exotic forms of iron instead of only one. These forms of iron seem to be alloyed with silicon, a lighter element.

Scientists had previously determined some of the characteristics of the iron in the core from the way seismic waves travel through Earth from earthquakes and explosives.

The University of Chicago research team used a laser-heated diamond anvil cell to expose a sample of iron to searing subsurface temperatures of approximately 4,200 degrees Fahrenheit and crushing pressures of 840,000 atmospheres. Using the APS helped researchers identify the samples’ chemical composition.

The researchers found that the atomic structure of iron changes under intense temperatures and pressures. A tiny iron sample may take on two different atomic structures under conditions found 1,800 miles beneath Earth’s surface.

The existence of two exotic forms of iron in the Earth’s core could influence the interpretation of seismic data about the core. The research results were reported in Science.

Cleaning up the environment
Researchers used an X-ray microprobe at the APS to examine the microbial processes that strip zinc and other toxic metals from solutions to produce acceptable drinking water.

The microbes convert metal sulfates into harmless sulfides. The results show how microbes control metal concentrations in groundwater and wetland-based remediation systems and suggest biological routes for formation of some low-temperature zinc sulfide deposits. The researchers are from the University of Wisconsin at Madison, the Australian Geological Survey Organization, Diversion Scuba of Madison and Argonne.

The microbes were first discovered by recreational scuba divers from Diversion Scuba exploring the dark, flooded tunnels of an old mine in southwestern Wisconsin.

This evidence can help develop strategies for creating new wetlands, rich in organic matter and to treat acidic drainage from mines. Acid mine drainage is a threat to surface and groundwater near mines and can contaminate wells and other drinking water supplies.

Seeing an important membrane protein
Proteins on cell membranes present a challenge to biologists because they are often large and insoluble, making them difficult to examine in detail. A team of structural biologists at Harvard’s Massachusetts General Hospital, working at the APS, has overcome these obstacles and for the first time determined the structure of aVb3, one of the many integrin proteins.

Integrin proteins are important because they control many cellular activities and are believed to play a major role in tumor growth, bone maintenance and inflammation. In addition, some viruses, including AIDS, enter cells through the integrin.

Knowing the structure should help scientists determine how the protein works and help pharmaceutical companies design drugs to combat diseases.

The X-ray analysis confirmed some suspicions about the integrin structure, but it also contained some surprises for the researchers, showing some bending in parts of the molecules. This bending might help explain how the integrin transmits its signals.

Pharmaceutical companies are already using this information in developing new drugs aimed at the protein.

For more information, please contact Catherine Foster.

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