May 20, 2013
Researchers Discover Evidence For How Life May Have Begun
John P. Millis, Ph.D. for redOrbit.com — Your Universe Online
One of the key elements to understanding the proliferation of life on Earth is modeling how electron transfer — the passage of an electron from one element to another — can be catalyzed. But the environmental conditions on Earth some 3 billion years ago were much different than they are today.
For one, there was a distinct lack of molecular oxygen in the atmosphere, because it is readily absorbed and therefore needs to be continually replenished. Not until the process of photosynthesis did molecular oxygen therefore become available.
In this case, though, that turns out to be a good thing because prior to when diatomic oxygen entered the scene the crust of the Earth contained great amounts of soluble iron that would later rust and become banded. It is also at this time where biologists believe that RNA played a much larger role in the evolution of life.
"Our study shows that when RNA teams up with iron in an oxygen-free environment, RNA displays the powerful ability to catalyze single electron transfer, a process involved in the most sophisticated biochemistry, yet previously uncharacterized for RNA," said Loren Williams, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology.
Williams and Chiaolong Hsiao, a Georgia Tech postdoctoral fellow in the School of Chemistry and Biochemistry, prepared peroxidase assays to detect electron transfer in solutions of RNA with various iron and magnesium ions. Of the 10 different types of RNA that were tested, they found that the two oldest forms - 23S ribosomal RNA and transfer RNA — had the two strongest electron transfer rates. Interestingly, none of the magnesium ions catalyzed electron transfer in any of the RNA types.
"Our findings suggest that the catalytic competence of RNA may have been greater in early Earth conditions than in present conditions, and our experiments may have revived a latent function of RNA," added Williams.
The research was published on May 19, 2013, in the journal Nature Chemistry.