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 聽identified a plausible way to generate the two purine nucleosides, adenosine and guanosine 鈥� A and G in the genetic code.
Now a team led by , 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 鈥� a stepwise process that generally yields a useless mess of many possible configurations.
Instead, Carell鈥檚 team started with even simpler precursors and let the whole process unfold at once, under mildly acidic conditions that mimicked early Earth.聽Their approach worked, producing high yields of adenosine. Guanosine can then easily be made from this.
Better yet, Carell鈥檚 starting points 鈥� formic acid and molecules called aminopyrimidines 鈥� or their precursors have been found on comets, and thus were probably available at the origin of life.
Path of life
鈥淲e now have a pathway that would allow us to use simple molecules that were likely present on the early Earth,鈥� says Carell. The next step is to link the bases into a full-length RNA strand, he says.
Carell鈥檚 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 , a chemist at the Georgia Institute of Technology in Atlanta.
Moreover, Carell鈥檚 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:
Read more: Why 鈥楻NA world鈥� theory on origin of life may be wrong after all;
First life: The search for the first replicator
