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June 4, 2002

For more information on these science news and feature story tips, contact the public information officer listed at (703) 292-8070. Editor: Josh Chamot

Colorado Alpine Lakes Show Troubling Changes

Researchers believe atmospheric nitrogen from auto emissions and agriculture on the heavily populated Front Range of the Colorado Rockies is causing increased algal growth in high alpine lakes.

Scientist Diane McKnight of the University of Colorado at Boulder found that, since about 1940, nitrogen enrichment and climatic changes have resulted in more algae, shifts in the dominant algal species, and the accumulation of organic sediment in a lake known as Green Lake 4.

"Over the past 20 years, nitrogen deposition has increased in the Green Lakes Valley watershed and the lake ice cover has become progressively thinner," said McKnight, whose research is supported by the National Science Foundation (NSF).

The five lakes in Green Lakes Valley - including Green Lake 4, at 11,500 feet above sea level - account for about 40 percent of Boulder's water supply. "The City of Boulder owns the watershed and makes a substantial effort to protect the water quality of the lakes, including a ban on hikers," McKnight said. "But there are no means for the city to protect the watershed from atmospheric . . . influences on water quality."

Similar trends have been observed in alpine lakes in Rocky Mountain National Park about 20 miles to the north, McKnight said. The Green Lakes study is part of NSF's Long-Term Ecological Research (LTER) program, a network of more than 20 sites in North America and Antarctica where researchers document ecological and climate changes over decades and centuries.

Results of the Green Lake 4 study indicate that more algal growth in the lake can occur at lower nitrogen levels than those that could cause acidification, McKnight said. They also suggest tougher standards than those proposed may be needed to protect water quality in alpine lakes on the Front Range, many of which are sources of water for Front Range communities in Colorado. [Cheryl Dybas]

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New Computational Method Could Shorten Time to Develop New Drugs

Researchers have devised a new way to simulate the interactions between drugs and the molecules they target. The new computer model treats the target molecules as flexible structures that stretch and bend, rather than as rigid objects, potentially improving the accuracy and speed of pharmaceutical tests.

"The race is on between sophisticated lab procedures and their computational analogs," said team leader J. Andrew McCammon of the University of California, San Diego (UCSD). "Our method both verifies and competes with costly lab methods that rely on thousands of trials."

Drugs are typically small molecules (called ligands) that bind tightly to a targeted protein (a receptor) and disrupt the protein's activity. Modern drug designers look for the binding sites, and until now used rigid crystal models for the search. In nature, target proteins are dynamic, flexing molecules.

For their study, funded in part by NSF, McCammon's group used computers at NSF's San Diego Supercomputer Center (SDSC) and an SDSC "satellite site" at UCSD.

The UCSD approach is called the 'relaxed-complex' scheme because the computational scheme allows the receptor protein to relax into any possible conformation. The team then tests various scenarios of ligand and receptor, determining which potential drug binds best to the target protein. "This allows us to use a building-block approach to constructing the best ligands," said Jung-Hsin Lin, a researcher in McCammon's group.

The method could be applied to every conceivable type of drug for which there are three-dimensional structures or predicted structures for the target to which the drug would bind. While it is computationally intensive, McCammon pointed out that by avoiding a brute-force approach in the lab (involving protein synthesis and purification, synthesis of the many ligands, and a large number of trials), drug designers may be able to save both time and money by using the new method. [Cheryl Dybas]

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Seafloor Observatories to Monitor Tsunamis, Earthquakes

New observatories equipped with various instruments, including seismometers, are being built deep below the seabed under the auspices of the Ocean Drilling Program (ODP), which is funded principally by NSF, with substantial contributions from international partners. The project will allow scientists to continuously monitor and record information and develop a long-term understanding of geological hazards such as tsunamis and major earthquakes.

These observatories, funded in part by NSF, fill an important void in scientific monitoring, say researchers. On land, the Global Seismic Network (GSN) provides adequate earthquake monitoring capabilities for most continental regions and islands, but large areas of the ocean floor have remained unmonitored until now.

The U.S. Global Seismic Network and its international affiliate, the Federation of Digital Seismic Networks, operate nearly 200 seismic stations, said scientist John Orcutt of the Scripps Institution of Oceanography.

"Even though nearly every island has a modern seismic observatory, enormous gaps in the coverage exist, limiting scientific and operational coverage for seismic studies of sources and the deep interior of the Earth," said Orcutt.

An ODP expedition on the research ship JOIDES Resolution (Leg 203) next month will drill a hole in the seafloor of the Pacific Ocean that will serve as the location of a future observatory.

The observatory's instrumentation will connect to the Internet through a satellite communications telemetry link. The site is more than 1200 miles from any other seismic observatory and will provide important information on earthquakes affecting Central and South America.

"This station and other future installations at sea will greatly enhance the coverage for these particularly threatening earthquakes," Orcutt said. [Cheryl Dybas]

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Frequency of Undersea Earthquakes Tied to Ocean Tides

Scientists studying an active seafloor volcano in the Pacific Ocean have determined that there is a correlation between hundreds of micro-earthquakes and ocean tides.

In research funded by NSF, geophysicist Maya Tolstoy of the Lamont-Doherty Earth Observatory at Columbia University found that earthquakes coming from the Axial Volcano on the Juan de Fuca Ridge (located off the coasts of Washington and Oregon) are occurring during tidal flows when the weight of the water is at a minimum.

Tolstoy and colleagues also found a tidal correlation with signals for harmonic tremors, which researchers believe result from super-heated water moving in cracks in Earth's crust. The results suggest that seafloor crust is essentially breathing with the ebb and flow of ocean tides, allowing more movement of water through the crust and the release of seismic energy on a regular tidal schedule.

"Scientists have long postulated that earthquakes and tidal movements are somehow connected," said Tolstoy, "but the link has been difficult to identify. It's only within the last decade that the technology has been available to make the long-term seismic recordings of the seafloor necessary to finding this correlation. We now have an interesting and important view into how Axial Volcano's deformation, and perhaps the deformation of other undersea volcanoes, actually works." [Cheryl Dybas]

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