ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Thursday, August 8, 1996 TAG: 9608080028
SECTION: NATIONAL/INTERNATIONAL PAGE: A-4 EDITION: METRO
DATELINE: NEW YORK
SOURCE: Associated Press
Boosting a theory of how life on Earth first emerged from the primordial soup, scientists have discovered that a short chain-like molecule can reproduce itself in the test tube.
Most scientists believe that some kind of self-reproducing molecule was needed for life to emerge. Its job would be to pass information from one generation to the next. Nowadays, that job is generally handled by DNA.
Popular theory says that originally, a chemical cousin of DNA called RNA may have been the reproducing molecule that let life emerge.
But the new research supports the less popular theory that molecules called peptides may have played that role instead. Scientists found that a peptide was able to promote the formation of new copies of itself.
Scientists should seriously consider a possible role for peptides in the origins of life, said researcher M. Reza Ghadiri of the Scripps Research Institute in La Jolla, Calif. He and colleagues presented the work in Thursday's issue of the journal Nature.
The result is surprising and exciting, said Stanley L. Miller of the University of California at San Diego. While scientists have usually focused on the replicating ability of RNA and DNA, he said, ``this brings another viewpoint into this, with considerable potential.''
Peptide reproduction would be fundamentally different from the way RNA and DNA reproduce, said Dr. Stuart Kauffman of the Santa Fe Institute in New Mexico.
DNA or RNA are strands that form the famous double helix structure. To reproduce, the two strands of the helix separate. An enzyme creates new strands, piece by piece, by using each building block on the original strands as a guide for choosing the next block to add to the growing new strands.
In contrast, Kauffman said, the peptide in the new research encourages the production of new copies of itself by joining two chain-like fragments end-to-end. The combined fragments are a new copy. Miller noted that the peptide did not reproduce itself from scratch. Rather, it joined two existing fragments, one with 15 chemical links, the other with 17.
Kauffman cautioned that the molecule's self-reproduction might be a ``chemical quirk'' that few peptides can do. But the results still raise the possibility that peptides provided the reproducing ability that led to life, he said.
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