Scientists have long wondered how life could have erupted from the primordial soup of organic material billions of years ago.
Researchers hypothesized that RNA, which is similar to DNA but with a simpler structure, could have been the catalyst. The problem with this idea is that RNA itself is made of four chemicals (adenine, guanine, cytosine, uracil), called nucleotides and usually abbreviated to A, G, C and U — but these are components that don't spontaneously assemble in water. Origin-of-life scientists speculate that a kind of proto-RNA could have emerged first.
Science Magazine reports that researchers in Spain and the U.S. are experimenting to see whether or not proto-RNA might have eventually evolved toward RNA. Nicholas Hud, a chemist at Georgia Tech, told Science Magazine that because RNA is so perfect, "it has to be the product of evolution."
Some chemical candidates for proto-RNA include cyanuric acid (CA) and triaminopyrimidine (TAP). When placed in an organic solvent, the chemicals would form rings, or rosettes, and these rosettes would stack on top of each other to make long strands. In water, CA and TAP clump together and fall out of the solution.
To make the process of self-assembly possible in water, Hud and his colleagues at the Institute for Research in Biomedicine in Barcelona tweaked TAP, giving it a short chemical tail and turning it into a chemical they dubbed TAPAS. Chemicals under a certain size have hydrophobic properties, so tweaking TAP and increasing its surface area allowed it to form rosettes with CA, and as many as 18,000 TAPAS and CA components to stack themselves into long chains.
This experiment does not prove that CA and TAP were the components of proto-RNA definiteively, but it does offer a possible explanation for how life first emerged from an eclectic mix of organic material. The next step, Hud said, was to see if these chains can encode genes and evolve from stacks into the double-helix structure of DNA and RNA.
Hud's research, titled "Efficient Self-Assembly of Long Noncovalent Polymers by Nucleobase Analogues," was reported in the Journal of the American Chemical Society.
