Strand of life Science Photo Library
One of the hardest steps in the origin of life on Earth may be easier than chemists thought.
RNA, or something very like it, has long been a strong candidate as the first self-replicating molecule in the origin of life. This is because it can both catalyse chemical reactions and carry genetic information.
But chemists first needed to explain how a large, complex molecule like RNA could form spontaneously to begin the process. They had done so for some, but not all, components of the RNA molecule.
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The biggest sticking point was that until now, no one had identified a plausible way to generate the two purine nucleosides, adenosine and guanosine – A and G in the genetic code.
Now a team led by Thomas Carell, an organic chemist at the Ludwig Maximilian University of Munich in Germany, may have found a method.
Previous efforts made the parts of a nucleoside separately and then linked them together – a stepwise process that generally yields a useless mess of many possible configurations.
Instead, Carell’s team started with even simpler precursors and let the whole process unfold at once, under mildly acidic conditions that mimicked early Earth. Their approach worked, producing high yields of adenosine. Guanosine can then easily be made from this.
Better yet, Carell’s starting points – formic acid and molecules called aminopyrimidines – or their precursors have been found on comets, and thus were probably available at the origin of life.
Path of life
“We now have a pathway that would allow us to use simple molecules that were likely present on the early Earth,” says Carell. The next step is to link the bases into a full-length RNA strand, he says.
Carell’s discovery removes one of the key stumbling blocks to RNA-based scenarios of the origin of life, whether they involve RNA alone or in concert with primitive proteins, says Nicholas Hud, a chemist at the Georgia Institute of Technology in Atlanta.
Moreover, Carell’s chemical reaction should work equally well with more primitive, RNA-like molecules, making it an excellent candidate for the prebiotic world, says Hud.
Journal reference: Science, DOI: 10.1126/science.aad2808
Read more: Why ‘RNA world’ theory on origin of life may be wrong after all;
First life: The search for the first replicator
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