 |
      |
 |
 |
||
 |
|
 |
||
 |
|
 |
||
|
For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. Editor: Amber Jones Contents of this News Tip:
Indian Ocean Pollution Substantially Cuts Sunlight Reaching Earth's SurfaceParticles of soot produced in southern Asia significantly reduce the amount of sunlight reaching Earth's surface, and the effect may have important consequences for the region's climate. That observation is drawn from recent results of the international Indian Ocean Experiment supported by the National Science Foundation (NSF). V. Ramanathan and S.K. Satheesh of the Center for Clouds, Chemistry and Climate, an NSF Science and Technology Center at the University of California at San Diego, used satellite and surface measurements to pinpoint a three-fold decrease in the solar radiation reaching the earth's surface from the amount reaching the upper atmosphere. The difference, the authors say, is largely due to manmade soot aerosol particles that absorb sunlight in the atmosphere. "The atmospheric heating over the northern Indian Ocean is surprisingly
large compared to other oceanic regions and is comparable in magnitude
with that observed over the coastal regions of the Atlantic Ocean," said
Ramanathan. The authors propose that the disruption caused by the soot
aerosols may affect the region's climate by slowing the natural hydrological
cycle and breaking up cloud cover. Although the researchers documented
aerosol particles such as sulfate, nitrate, organics and ash, the sunlight
absorption is largely due to combustion-derived soot. NSF Links U.S., Russian Researchers Through "MIRNET"The NSF has established a high-performance network connection between the United States and research institutions in Russia. Jointly funded by NSF and the Russian Ministry for Science and Technology, MIRnet delivers next-generation Internet services for scientific and educational collaborations. The five-year, $6.5-million project transfers data between Moscow and NSF's international STAR TAP network hub in Chicago at speeds up to 6 million bits per second. The ATM (asynchronous transfer mode) connection became active in mid-1999 and supports applications such as data visualization, remote control of instrumentation, medical imaging and high-quality video conferencing. MIRnet is accessible to 177 U.S. institutions that have received NSF High-Performance Connections grants for linking to the vBNS (veryhigh-performance Backbone Network System) or another research network. Russian participants include the Institute for Public Networks, the Academy of Science, Moscow State University, Friends and Partners-Russia and the VUZTelecom Center of St. Petersburg. Transatlantic telecommunications services are provided by Teleglobe, Inc., and the Russian provider Rascom. [Tom Garritano] For more information, see: http://www.friends-partners.org/friends/mirnet/ Inner Workings of Protein Machinery That Feeds Bacteria UnraveledCell membranes are active barriers that protect the interiors of living cells from the molecular environments outside the cells. Within the membranes are proteins that passively allow the movement of critical nutrients and electrolytes into the cell interior and other proteins that act like pumps to transport needed molecules into the cytoplasm of the cell. The action of these tiny molecular pumps remains largely a mystery, but scientist David Cafiso of the University of Virginia has taken an important step in increasing biologists' understanding of their activity. Cafiso observed the first steps in the action of a protein called BtuB that actively transports vitamin B12 across the outer membrane of E. coli. Though the B12 is coming from outside the cell, the energy needed to pump it comes from the cell interior. Cafiso studied how the protein transmits the energy across the membrane so that it can initiate the pumping process. He first demonstrated that the protein changes shape in response to B12 binding on the outside of the membrane. This shape change transmits a simple message across the membrane: "B12 is bound," putting the molecule in a state that allows it to utilize energy in the pumping process. Next, he found that shape changes at both ends of the molecule are required to initiate the active transport of B12. Once the molecule knows that vitamin B12 has bound to the outside, it acts like a spring being released, pushing the pump into action. "Protein pumps are major players in a host of physiological processes," says Kamal Shukla, director of NSF's biophysics program, which funded the research. "The transport of nutrients and electrolytes though cell membranes is a critically important process for all living organisms. The success of this study represents a major first step in understanding their action at the molecular level." [Cheryl Dybas]
|
||||
 |
|
 |
|
|
 |