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sábado, maio 08, 2010

Peptides May Hold 'Missing Link' to Life

ScienceDaily (May 7, 2010) — Emory scientists have discovered that simple peptides can organize into bi-layer membranes. The finding suggests a "missing link" between the pre-biotic Earth's chemical inventory and the organizational scaffolding essential to life.

Researchers tagged one end of peptide chains with an NMR label, and then allowed them to assemble to see if the ends would interact. The result was a bi-layer membrane with inner and outer faces and an additional, buried layer that localized functionality within the interior. (Credit: Image courtesy of Emory University)

"We've shown that peptides can form the kind of membranes needed to create long-range order," says chemistry graduate student Seth Childers, lead author of the paper recently published by the German Chemical Society's Angewandte Chemie. "What's also interesting is that these peptide membranes may have the potential to function in a complex way, like a protein."

Chemistry graduate student Yan Liang captured images of the peptides as they aggregated into molten globular structures, and self-assembled into bi-layer membranes. The results of that experiment were recently published by the Journal of the American Chemical Society.

"In order to form nuclei, which become the templates for growth, the peptides first repel water," says Liang, who is now an Emory post-doctoral fellow in neuroscience. "Once the peptides form the template, we can now see how they assemble from the outer edges."

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Many groups studying the origins of life have focused on RNA, which is believed to have pre-dated living cells. But RNA is a much more complicated molecule than a peptide. "Our studies have now shown that, if you just add water, simple peptides access both the physical properties and the long-range molecular order that is critical to the origins of chemical evolution," Childers says.

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