////////////////////Study suggests how DNA building block might have formed
Nov. 2, 2007Courtesy University of Georgiaand World Science staff
Many experiments have shown it: simple molecules can combine chemically—outside of living things—to form the building blocks of DNA, the key component of life. But just how this combination occurs is unknown. Scientists want to find out, since that might explain how DNA originated.
The basic structure of DNA. (Courtesy U.S. Nat'l Library of Medicine)
Now, chemists have proposed what they call the first detailed, feasible account of how one of DNA’s major building blocks could have arisen on an early, lifeless Earth. The necessary ingredients: five cyanide molecules, they said.Just where “biomolecules,” such as DNA’s components, originated isn’t known, said University of Georgia chemist Paul von Ragué Schleyer, one of the researchers. “One can only speculate. They could have formed from smaller molecules present on primitive Earth, either very slowly over millions of years or rapidly before the Earth cooled down. Asteroids may have brought them from outer space,” he added, thought this doesn’t explain how they would have formed there.DNA is life’s molecular blueprint, passed from generation to generation. First isolated in 1869 by a Swiss doctor from pus in discarded bandages, DNA’s structure was discovered in 1953. It’s shaped somewhat like a twisted ladder with rungs anchored by interlocking pairs of two out of four molecules, known as nucleic acid bases. The four are adenine, guanine, cytosine and thymine.Schleyer’s team focused on adenine because of its prevalence and ability to form from simple components in the dark. Along with other building blocks of life, adenine has even been detected in outer space, though there, the great distances among its smaller molecular ingredients make its emergence trickier to explain.But many experiments have shown that simulated primitive Earth conditions can lead to the formation of essential compounds of life including amino acids, nucleotides and carbohydrates, the researchers wrote in their study. The work was published Oct. 30 in the scientific journal Proceedings of the National Academies of Science.Remarkably, they said, adenine has been found to arise from highly poisonous cyanide dissolved in ammonia and frozen in a refrigerator for 25 years. A high-temperature experiment designed to simulate early volcano-like environments also produced adenine. But the question is how.Schleyer’s team devised an answer by solving a series of key riddles. They worked out processes in which five cyanide molecules might combine to make adenine under terrestrial conditions. The proposal was based on computer-assisted studies that involved quantum mechanics, the sometimes illogical-seeming rules that govern atomic interactions.The researchers said the report provides a more detailed understanding of some of the processes of “chemical evolution,” and a partial answer to the basic question of how life’s chemistry emerged. The investigation should trigger similar probes into the origins of the three remaining bases and of other biologically relevant molecules, they added.
CREDIT=http://www.world-science.net/othernews/071102_adenine.htm
////////////////////MOVING STORY OF HUMAN GREED=Heroes star Hayden's surfboard protest fails to stop dolphin bloodbathLast updated at 09:27am on 2nd November 2007
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Heroes star Hayden Panettiere wept yesterday after watching the salvage slaughter of a pod of dolphins.
The actress was among 30 protesters who paddled on surfboards to block mounted an extraordinary attack on Japanese fisherman during their annual dolphin massacre.
But before the Australian and American surfers could reach the dolphins, a fishing boat intervened using the boat's propellers to block their way.
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