Large Asteroid Breakup May Have Caused Mass Extinction On Earth 65 Million Years Ago

Source:

http://www.sciencedaily.com/releases/2007/09/070906135629.htm

Science Daily — The impactor believed to have wiped out the dinosaurs and other life forms on Earth some 65 million years ago has been traced back to a breakup event in the main asteroid belt. A joint U.S.-Czech team from Southwest Research Institute (SwRI) and Charles University in Prague suggests that the parent object of asteroid (298) Baptistina disrupted when it was hit by another large asteroid, creating numerous large fragments that would later create the Chicxulub crater on the Yucatan Peninsula as well as the prominent Tycho crater found on the Moon.

The team of researchers, including Dr. William Bottke (SwRI), Dr. David Vokrouhlicky (Charles University, Prague) and Dr. David Nesvorny (SwRI), combined observations with several different numerical simulations to investigate the Baptistina disruption event and its aftermath. A particular focus of their work was how Baptistina fragments affected the Earth and Moon.
At approximately 170 kilometers in diameter and having characteristics similar to carbonaceous chondrite meteorites, the Baptistina parent body resided in the innermost region of the asteroid belt when it was hit by another asteroid estimated to be 60 kilometers in diameter. This catastrophic impact produced what is now known as the Baptistina asteroid family, a cluster of asteroid fragments with similar orbits. According to the team's modeling work, this family originally included approximately 300 bodies larger than 10 kilometers and 140,000 bodies larger than 1 kilometer.
Once created, the newly formed fragments’ orbits began to slowly evolve due to thermal forces produced when they absorbed sunlight and re-radiated the energy away as heat. According to Bottke, "By carefully modeling these effects and the distance traveled by different-sized fragments from the location of the original collision, we determined that the Baptistina breakup took place 160 million years ago, give or take 20 million years."
The gradual spreading of the family caused many fragments to drift into a nearby "dynamical superhighway" where they could escape the main asteroid belt and be delivered to orbits that cross Earth’s path. The team's computations suggest that about 20 percent of the surviving multi-kilometer-sized fragments in the Baptistina family were lost in this fashion, with about 2 percent of those objects going on to strike the Earth, a pronounced increase in the number of large asteroids striking Earth.
Support for these conclusions comes from the impact history of the Earth and Moon, both of which show evidence of a two-fold increase in the formation rate of large craters over the last 100 to 150 million years. As described by Nesvorny, "The Baptistina bombardment produced a prolonged surge in the impact flux that peaked roughly 100 million years ago. This matches up pretty well with what is known about the impact record."
Bottke adds, "We are in the tail end of this shower now. Our simulations suggest that about 20 percent of the present-day, near-Earth asteroid population can be traced back to the Baptistina family."
The team then investigated the origins of the 180 kilometer diameter Chicxulub crater, which has been strongly linked to the extinction of the dinosaurs 65 million years ago. Studies of sediment samples and a meteorite from this time period indicate that the Chicxulub impactor had a carbonaceous chondrite composition much like the well-known primitive meteorite Murchison. This composition is enough to rule out many potential impactors but not those from the Baptistina family. Using this information in their simulations, the team found a 90 percent probability that the object that formed the Chicxulub crater was a refugee from the Baptistina family.
These simulations also showed there was a 70 percent probability that the lunar crater Tycho, an 85 kilometer crater that formed 108 million years ago, was also produced by a large Baptistina fragment. Tycho is notable for its large size, young age and its prominent rays that extend as far as 1,500 kilometers across the Moon. Vokrouhlicky says, "The probability is smaller than in the case of the Chicxulub crater because nothing is yet known about the nature of the Tycho impactor."
This study demonstrates that the collisional and dynamical evolution of the main asteroid belt may have significant implications for understanding the geological and biological history of Earth.
As Bottke says, "It is likely that more breakup events in the asteroid belt are connected in some fashion to events on the Earth, Moon and other planets. The hunt is on!"
The article, "An asteroid breakup 160 Myr ago as the probable source of the K/T impactor," was published in the Sept. 6 issue of Nature.
The NASA Origins of Solar Systems, Planetary Geology and Geophysics, and Near-Earth Objects Observations programs funded Bottke's and Nesvorny's research; Vokrouhlicky was funded by the Grant Agency of the Czech Republic.
Note: This story has been adapted from a news release issued by Southwest Research Institute.

Fausto Intilla

www.oloscience.com

‘Bringing the Ocean to the World,’ in High-Def

Source:

http://www.nytimes.com/2007/09/04/science/04ocea.html?ref=science

By WILLIAM YARDLEY
Published: September 4, 2007

SEATTLE — Thousands of miles of fiber-optic cables are strung across the world’s oceans, connecting continents like so many tin cans in this age of critical global communication. So the fact that about 800 more miles of fiber-optic cable will soon thread the sea floor off the coast of the Pacific Northwest might not seem particularly revolutionary. Until you meet John R. Delaney, part oceanographer, part oracle.

“This is a mission to Planet Ocean,” said Mr. Delaney, a professor at the University of Washington. “This is a NASA-scale mission to basically enter the Inner Space, and to be there perpetually. What we’re doing is bringing the ocean to the world.”
Under a $331 million program long dreamed of by oceanographers and being financed by the National Science Foundation, Professor Delaney and a team of scientists from several other institutions are leading the new Ocean Observatories Initiative, a multifaceted effort to study the ocean — in the ocean — through a combination of Internet-linked cables, buoys atop submerged data collection devices, robots and high-definition cameras. The first equipment is expected to be in place by 2009.
A central goal, say those involved, is to better understand how oceans affect life on land, including their role in storing carbon and in climate change; the causes of tsunamis; the future of fish populations; and the effect of ocean temperature on growing seasons. Oceanographers also hope to engage other scientists and the public more deeply with ocean issues by making them more immediate. Instead of spending weeks or months on a boat gathering data, then returning to labs to make sense of it, oceanographers say they expect to be able to order up specific requests from their desktops and download the results.
Researchers will be able, for example, to assemble a year’s worth of daily data on deep ocean temperatures in the Atlantic or track changes in currents as a hurricane nears the Gulf of Mexico. And schoolchildren accustomed to dated graphics and grainy shark videos will only have to boot up to dive deep in high definition. “It’ll all go on the Internet and in as real time as possible,” said Alexandra Isern, the program director for ocean technology at the National Science Foundation. “This is really going to transform not only the way scientists do science but also the way the public can be involved.”
The program has three main parts, two of which involve placing a range of sensors in the oceans and one that connects through the Internet all the information gathered, so that the public and scientists can have access to it.
A “coastal/global” program will include stand-alone deep-water data-gathering stations far offshore, mostly in the higher latitudes of the Atlantic and Pacific, where cold, rough conditions have made ship-based oceanography difficult.
In American waters, observation systems are planned on both coasts. In the Pacific, off the Oregon coast, the system will study the upwelling of cold water that has led to repeated “dead zones” of marine life in recent summers. In the East, off Martha’s Vineyard, a coastal observation system is planned along the continental shelf, gathering information at the surface, subsurface and on the sea floor, where warm Gulf Stream currents confront colder water from off the coast of Canada.
“That mixing affects surface productivity, weather, carbon cycling,” said Robert S. Detrick, a senior scientist at Woods Hole Oceanographic Institution.
In August, the Joint Oceanographic Institutions, which is administering the Ocean Observatories Initiative for the National Science Foundation, chose Woods Hole to lead the offshore buoy and coastal program. Woods Hole, which will receive about $98 million of the total cost, will partner with the Scripps Institution of Oceanography at the University of California, San Diego, and Oregon State University’s College of Oceanic and Atmospheric Sciences.
In the Northwest, about $130 million of the initiative’s cost is being dedicated to build a regional observatory, a series of underwater cables that will crisscross the tectonic plate named for the explorer Juan de Fuca. Rather than provide an information superhighway that bypasses the ocean, this new network is being put in place to take its pulse. Professor Delaney, whose specialty is underwater volcanoes that form at the seams between tectonic plates and the surprising life those seams support, is among those who have been pursuing the cable network for more than a decade, overcoming hurdles of money, technology and skepticism.
Some scientists have suggested that the Juan de Fuca is an imperfect laboratory, that it is small and lacks some features, like the most intense El Niño fluctuations, that might reveal more about how that phenomenon affects conditions at sea and on land. But Professor Delaney says the Juan de Fuca plate is well-suited for the program precisely because it is self-contained, just offshore and rich with seafloor activity, complicated current patterns and abundant fish and marine mammals. The new network shares many similarities with a plan called Neptune that Professor Delaney and others began pushing for in the 1990s. As part of an earlier effort related to that project, Canada is moving forward with its own cabled network off the coast of British Columbia.
“For the first three or four years, people just laughed when I said we’re going to turn Juan de Fuca Plate into a national laboratory,” Professor Delaney said. “Now they’re not laughing.”

Many oceanographers say the program will transform their field. Oscar Schofield, a biological oceanographer at Rutgers University, has spent nearly a decade helping piece together a small-scale coastal observatory in the Atlantic using a combination of radar, remote-controlled underwater gliders and a 15-kilometer underwater cable. The program, called the Coastal Ocean Observation Lab, which he runs with Scott Glenn, also a professor at Rutgers, has a Web site where outsiders can track currents, water temperatures and salinity levels in parts of the Atlantic. They can also follow measuring instruments guided remotely from the New Jersey coast to south of the Chesapeake Bay.

Professor Schofield said that the data gathered already had upended some of what he was taught in graduate school, from the way rivers flow into the ocean to the complexity of surface currents.
“When there’s a hurricane, when all the ships are running for cover, I’m flying my gliders into the hurricane,” using his office computer, Professor Schofield said. “Then I’m sitting at home drinking a beer watching the ocean respond to a hurricane.”
He added: “What’s great about oceanography is we’re still in the phase of just basic exploration. We’ve discovered things off one of the most populated coasts in the United States that we didn’t know yet. O.O.I. will take us one level beyond that, to where any scientist in the world will be able to explore any ocean.”
Several scientists involved in the project cited improved technology — from increased bandwidth to the ability to provide constant power to instruments at sea by underwater cables or solar or wind power — as critical to making the new program possible. They also say that increased concern about global warming, storms and fisheries has brought new attention to their field.
Some experts say they wish the project included more money for, say, placing buoys in the Indian Ocean, where monsoons and other events make for rich ocean activity. But John A. Orcutt, a professor at Scripps who is directing the effort to link the new research to the Internet, said being able to provide constant new data to scientists around the world, or even to teenagers surfing YouTube, will help build support for expanding the project in the future.
“We want to get the oceans and the sea floor in front of the public now,” Professor Orcutt said, “so they can understand the need for more.”

Fausto Intilla

www.oloscience.com

Earthquakes in Real Time! (Place & Hour)

LINK to see the Real Time Map:

http://earthquake.usgs.gov/eqcenter/recenteqsww

Fausto Intilla (Scientific Popularizer) - www.oloscience.com

NASA Satellites Eye Coastal Water Quality

Source:

http://www.sciencedaily.com/releases/2007/08/070829162748.htm

Science Daily — Using data from instruments aboard NASA satellites, Zhiqiang Chen and colleagues at the University of South Florida in St. Petersburg, found that they can monitor water quality almost daily, rather than monthly.

Such information has direct application for resource managers devising restoration plans for coastal water ecosystems and federal and state regulators in charge of defining water quality standards.
The team's findings, published July 30 in two papers in Remote Sensing of Environment, will help tease out factors that drive changes in coastal water quality. For example, sediments entering the water as a result of coastal development or pollution can cause changes in water turbidity -- a measure of the amount of particles suspended in the water. Sediments suspended from the bottom by strong winds or tides may also cause such changes. Knowing where the sediments come from is critical to managers because turbidity cuts off light to the bottom, thwarting the natural growth of plants.
"If we can track the source of turbidity, we can better understand why turbidity is changing. And if the source is human-related, we can try to manage that human activity," says Frank Muller-Karger, a study co-author from the University of South Florida.
Satellites previously have observed turbidity in the open ocean by monitoring how much light is reflected and absorbed by the water. The technique has not had much success in observing turbidity along the coast, however. That's because shallow coastal waters and Earth's atmosphere serve up complicated optical properties that make it difficult for researchers to determine which colors in a satellite image are related to turbidity, which to shallow bottom waters, and which to the atmosphere. Now with advances in satellite sensors combined with developments in how the data are analyzed, Chen and colleagues show it is possible to monitor turbidity of coastal waters via satellite.
The traditional methods of monitoring coastal water quality require scientists to use boats to gather water samples, typically on a monthly basis because of the high costs of these surveys. The method is sufficient to capture episodic events affecting water quality, such as seasonal freshwater runoff. Chen and colleagues suspected, however, that the monthly measurements were not capturing fast changes in factors that affect water quality, such as winds, tides and human influences including pollution and runoff.
The team set out to see if satellites could accurately measure two key indicators of water quality - turbidity and water clarity -- in Tampa Bay, Fla. An analysis of turbidity takes into account water clarity, a measure of how much light can penetrate into deep water. Satellites, with their wide coverage and multiple passes per week, provided a solution to frequent looks and measuring an entire estuary within seconds.
To determine water clarity in Tampa Bay, the team looked at more than eight years of imagery from GeoEYE's Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument, whose data is analyzed, processed and distributed by NASA for research. The images give a measure of how much light is reflected by the water. The data were put through a two-step calculation to arrive at a measure of clarity. Similarly, data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) instrument onboard the Aqua satellite was compared with measurements of turbidity gathered on the ground and then applied to each whole image to make the maps.
When compared with results from independent field measurements, collected with the help from the U.S. Geological Survey, the researchers found that the satellites offered an accurate measure of water quality in the bay. The method can be applied to coastal waters worldwide with little change in methods, according to Muller-Karger.
Frequent measurements from space could resolve questions about the specific timing and nature of events that led to decreases in water quality. Seasonal freshwater discharge from nearby rivers and runoff into the bay can carry nutrients. If these nutrients are not controlled, they can give rise to large and harmful phytoplankton blooms, which can kill sea grass. Wind conditions, however, are the driving force for a decline in water quality in the dry season between October and June, when bottom sediments are disturbed.
"It's important to look at baseline conditions and see how they change with the seasons and over the years, and whether that change is due to development, coastal erosion, the extraction and dumping of sediments, or digging a channel," Muller-Karger says.
The SeaWiFS sensor was launched aboard the OrbView-2 satellite in 1997 to collect ocean color data. MODIS was launched aboard the Aqua satellite in 2002. The instrument collects measurements from the entire Earth surface every one to two days.
Note: This story has been adapted from a news release issued by NASA/Goddard Space Flight Center.

Fausto Intilla

www.oloscience.com

Volcanoes Key To Earth's Oxygen Atmosphere

Source:

http://www.sciencedaily.com/releases/2007/08/070829143713.htm

Science Daily — A switch from predominantly undersea volcanoes to a mix of undersea and terrestrial ones shifted the Earth's atmosphere from devoid of oxygen to one with free oxygen, according to geologists.

"The rise of oxygen allowed for the evolution of complex oxygen-breathing life forms," says Lee R. Kump, professor of geoscience, Penn State.
Before 2.5 billion years ago, the Earth's atmosphere lacked oxygen. However, biomarkers in rocks 200 million years older than that period, show oxygen-producing cyanobacteria released oxygen at the same levels as today. The oxygen produced then, had to be going somewhere.
"The absence of oxidized soil profiles and red beds indicates that oxidative weathering rates were negligible during the Archaean," the researchers report in the Aug. 30 issue of Nature.
The ancient Earth should have had an oxygen atmosphere but something was converting, reducing, the oxygen and removing it from the atmosphere. The researchers suggest that submarine volcanoes, producing a reducing mixture of gases and lavas, effectively scrubbed oxygen from the atmosphere, binding it into oxygen containing minerals.
"The Archaean more than 2.5 billion years ago seemed to be dominated by submarine volcanoes," says Kump. "Subaerial andesite volcanoes on thickened continental crust seem to be almost absent in the Archaean."
About 2.5 billion years ago at the Archaean/Proterozoic boundary, when stabilized continental land masses arose and terrestrial volcanoes appeared, markers show that oxygen began appearing in the atmosphere.
Kump and Mark E. Barley, professor of geology, University of Western Australia, looked at the geologic record from the Archaean and the Palaeoproterozoic in search of the remains of volcanoes. They found that the Archaean was nearly devoid of terrestrial volcanoes, but heavily populated by submarine volcanoes. The Palaeoproterozoic, however, had ample terrestrial volcanic activity along with continuing submarine vulcanism. Subaerial volcanoes arose after 2.5 billion years ago and did not strip oxygen from the air. Having a mix of volcanoes dominated by terrestrial volcanoes allowed oxygen to exist in the atmosphere.
Terrestrial volcanoes could become much more common in the Palaeoproterozoic because land masses stabilized and the current tectonic regime came into play.
The researchers looked at the ratio of submarine to subaerial volcanoes through time. Because submarine volcanoes erupt at lower temperatures than terrestrial volcanoes, they are more reducing. As long as the reducing ability of the submarine volcanoes was larger than the amounts of oxygen created, the atmosphere had no oxygen. When terrestrial volcanoes began to dominate, oxygen levels increased.
The National Science Foundation, NASA Astrobiology Institute and the Australian Research Council supported this work.
Note: This story has been adapted from a news release issued by Penn State.

Fausto Intilla

www.oloscience.com

"The World without us"

Source: http://www.nytimes.com/2007/09/02/books/review/Schuessler-t.html?_r=1&ref=science&oref=slogin

Starting Over

By JENNIFER SCHUESSLER
Published: September 2, 2007

When Rachel Carson’s “Silent Spring” was published in 1963, the chemical giant Monsanto struck back with a parody called “Desolate Spring” that envisioned an America laid waste not by pesticides but by insects: “The bugs were everywhere. Unseen. Unheard. Unbelievably universal. ... On or under every square foot of land, every square yard, every acre, and county, and state and region in the entire sweep of the United States. In every home and barn and apartment house and chicken coop, and in their timbers and foundations and furnishings. Beneath the ground, beneath the waters, on and in limbs and twigs and stalks, under rocks, inside trees and animals and other insects — and yes, inside man.”

To Alan Weisman, this nightmare scenario would be merely a promising start. In his morbidly fascinating nonfiction eco-thriller, “The World Without Us,” Weisman imagines what would happen if the earth’s most invasive species — ourselves — were suddenly and completely wiped out. Writers from Carson to Al Gore have invoked the threat of environmental collapse in an effort to persuade us to change our careless ways. With similar intentions but a more devilish sense of entertainment values, Weisman turns the destruction of our civilization and the subsequent rewilding of the planet into a Hollywood-worthy, slow-motion disaster spectacular and feel-good movie rolled into one.
A journalist and author of three previous books, Weisman travels from Europe’s last remnant of primeval forest to the horse latitudes of the Pacific, interviewing everyone from evolutionary biologists and materials scientists to archaeologists and art conservators in his effort to sketch out the planet’s post-human future. In even the most heavily fortified corners of the settled world, the rot would set in quickly. With no one left to run the pumps, New York’s subway tunnels would fill with water in two days. Within 20 years, Lexington Avenue would be a river. Fire- and wind-ravaged skyscrapers would eventually fall like giant trees. Within weeks of our disappearance, the world’s 441 nuclear plants would melt down into radioactive blobs, while our petrochemical plants, “ticking time bombs” even on a normal day, would become flaming geysers spewing toxins for decades to come. Outside of these hot spots, Weisman depicts a world slowly turning back into wilderness. After about 100,000 years, carbon dioxide would return to prehuman levels. Domesticated species from cattle to carrots would revert back to their wild ancestors. And on every dehabitated continent, forests and grasslands would reclaim our farms and parking lots as animals began a slow parade back to Eden.
A million years from now, a collection of mysterious artifacts would remain to puzzle whatever alien beings might stumble upon them: the flooded tunnel under the English Channel; bank vaults full of mildewed money; obelisks warning of buried atomic waste (as current law requires) in seven long-obsolete human languages, with pictures. The faces on Mount Rushmore might provoke Ozymandian wonder for about 7.2 million more years. (Lincoln would probably fare better on the pre-1982 penny, cast in durable bronze.) But it’s hard to imagine an alien archaeologist finding poetry in the remote Pacific atolls awash in virtually unbiodegradable plastic bottles, bags and Q-tip shafts, or in the quadrillions of nurdles, microscopic plastic bits in the oceans — they currently outweigh all the plankton by a factor of six — that would continue to cycle uncorrupted through the guts of sea creatures until an enterprising microbe evolved to break them down.
As for the creatures who made this mess, the only residue of our own surprisingly negligible biomass — according to the biologist E. O. Wilson, the six billion-plus humans currently wreaking planetary havoc could all be neatly tucked away in one branch of the Grand Canyon — would be the odd fossil, mingling perhaps with the limbs of Barbie dolls.
Weisman knows from the work of environmental historians that humans have been shaping the natural world since long before the industrial age. His inner Deep Ecologist may dream of Earth saying good riddance to us, but he finds some causes for hope amid the general run of man-bites-planet bad news. At Amboseli National Park in Kenya, he takes comfort in the spectacle of Masai herdsmen living in carefully managed harmony with predators and grazers alike. In the 30-kilometer-radius “Zone of Alienation” around the Chernobyl nuclear plant, where some bridges remain too hot to cross 20 years after the 1986 meltdown, he finds eerie peace in the forests full of moose, lynx and radioactive deer. Watching from inside his protective suit as barn swallows buzz around the reactor, Weisman writes: “You want them to fly away, fast and far. At the same time, it’s mesmerizing that they’re here. It seems so normal, as if apocalypse has turned out to be not so bad after all. The worst happens, and life still goes on.”

So could we ourselves really simply fly away, leaving the rest of nature to slowly clean up our mess? Doomsday rhetoric aside, the fact is that nothing is likely to wipe us out completely, at least not without taking a good chunk of the rest of creation with us. (Even a virus with a 99.99 percent kill rate would still leave more than half a million naturally immune survivors who could fully repopulate the earth to current levels in a mere 50,000 years.) Not that some people aren’t trying to take matters into their own hands. Weisman checks in with Les Knight, the founder of the Voluntary Human Extinction Movement, which advocates gradually putting our species to sleep by collective refusal to procreate. After an initial panic, we would look around and see that the world was actually getting better: “With no more resource conflicts, I doubt we’d be wasting each other’s lives in combat,” Knight says. “The last humans could enjoy their final sunsets peacefully, knowing they have returned the planet as close as possible to the Garden of Eden.” (Apparently he never saw “Children of Men.”)

Weisman has his own flirtation with religious language, his occasionally portentous impassivity giving way to the familiar rhetoric of eco-hellfire as he imagines the earth’s most “narcissistic” species cleansed from the earth as punishment for its “overindulged lifestyle.” But Weisman stops short of calling for our full green burial, arguing instead for a universal “one child per human mother” policy. It would take until 2100 to dwindle to a global population of 1.6 billion, a level last seen in the 19th century, before leaping advances in energy, medicine and food production, but well before then we’d experience “the growing joy of watching the world daily become more wonderful.” And the evidence, Weisman writes, “wouldn’t hide in statistics. It would be outside every human’s window, where refreshed air would fill each season with more birdsong.”
Even readers who vaguely agree that there are “too many of us” (or is it too many of them?) may not all share Weisman’s brisk certainty that trading a sibling for more birdsong is a good bargain, just as those who applaud the reintroduction of the North American wolf may not quite buy the claim by Dave Foreman, a founder of Earth First!, that filling the New World’s empty über-predator niche with African lions and cheetahs is our best chance to avoid what Weisman calls “the black hole into which we’re shoving the rest of nature.” In the end, it’s the cold facts and cooler heads that drive Weisman’s cautionary message powerfully home. When it comes to mass extinctions, one expert tells him, “the only real prediction you can make is that life will go on. And that it will be interesting.” Weisman’s gripping fantasy will make most readers hope that at least some of us can stick around long enough to see how it all turns out.

Fausto Intilla

www.oloscience.com

Secrets Of Red Tide Revealed

Source:

http://www.sciencedaily.com/releases/2007/08/070830150106.htm

Science Daily — In work that could one day help prevent millions of dollars in economic losses for seaside communities, MIT chemists have demonstrated how tiny marine organisms likely produce the red tide toxin that periodically shuts down U.S. beaches and shellfish beds.

In the Aug. 31 cover story of Science, the MIT team describes an elegant method for synthesizing the lethal components of red tides. The researchers believe their method approximates the synthesis used by algae, a reaction that chemists have tried for decades to replicate, without success.
Understanding how and why red tides occur could help scientists figure out how to prevent the blooms, which cause significant ecological and economic damage. The New England shellfish industry, for example, lost tens of millions of dollars during a 2005 outbreak, and red tide killed 30 endangered manatees off the coast of Florida this spring.
The discovery by MIT Associate Professor Timothy Jamison and graduate student Ivan Vilotijevic not only could shed light on how algae known as dinoflagellates generate red tides, but could also help speed up efforts to develop cystic fibrosis drugs from a compound closely related to the toxin. Red tides, also known as algal blooms, strike unpredictably and poison shellfish, making them dangerous for humans to eat. It is unknown what causes dinoflagellates to produce the red tide toxins, but it may be a defense mechanism, possibly provoked by changes in the tides, temperature shifts or other environmental stresses.
One of the primary toxic components of red tide is brevetoxin, a large and complex molecule that is very difficult to synthesize.
Twenty-two years ago, chemist Koji Nakanishi of Columbia University proposed a cascade, or series of chemical steps, that dinoflagellates could use to produce brevetoxin and other red tide toxins. However, chemists have been unable to demonstrate such a cascade in the laboratory, and many came to believe that the "Nakanishi Hypothesis" would never be proven.
"A lot of people thought that this type of cascade may be impossible," said Jamison. "Because Nakanishi's hypothesis accounts for so much of the complexity in these toxins, it makes a lot of sense, but there hasn't really been any evidence for it since it was first proposed."
Jamison and Vilotijevic's work offers the first evidence that Nakanishi's hypothesis is feasible. Their work could also help accelerate drug discovery efforts. Brevenal, another dinoflagellate product related to the red tide toxins, has shown potential as a powerful treatment for cystic fibrosis (CF). It can also protect against the effects of the toxins.
"Now that we can make these complex molecules quickly, we can hopefully facilitate the search for even better protective agents and even more effective CF therapies," said Jamison.
Until now, synthesizing just a few milligrams of red tide toxin or related compounds, using a non-cascade method, required dozens of person-years of effort.
The new synthesis depends on two critical factors-giving the reaction a jump start and conducting the reaction in water.
Many red tide toxins possess a long chain of six-membered rings. However, the starting materials for the cascades, epoxy alcohols, tend to form five-membered rings. To overcome that, the researchers attached a "template" six-membered ring to one end of the epoxy alcohol. That simple step effectively launches the cascade of reactions that leads to the toxin chain, known as a ladder polyether.
"The trick is to give it a little push in the right direction and get it running smoothly," said Jamison.
The researchers speculate that in dinoflagellates, the initial jump start is provided by an enzyme instead of a template.
Conducting the reaction in water is also key to a successful synthesis. Water is normally considered a poor solvent for organic reactions, so most laboratory reactions are performed in organic solvents. However, when Vilotijevic introduced water into the reaction, he noticed that it proceeded much more quickly and selectively.
Although it could be a coincidence that these cascades work best in water and that dinoflagellates are marine organisms, water may nevertheless be directly involved in the biosynthesis of the toxins or emulating an important part of it, said Jamison. Because of this result, the researchers now believe that organic chemists should routinely try certain reactions in water as well as organic solvents.
The research was funded by the National Institute of General Medical Sciences, Merck Research Laboratories, Boehringer Ingelheim, and MIT.
"This is an elegant piece of work with multiple levels of impact," said John Schwab, who manages organic chemistry research for the National Institute of General Medical Sciences. "Not only will it allow chemists to synthesize this important class of complex molecules much more easily, but it also provides key insights into how nature may make these same molecules. This is terrific bang for the taxpayers' buck!"
Note: This story has been adapted from a news release issued by Massachusetts Institute of Technology.

Fausto Intilla

www.oloscience.com