The RNA world is a beautiful hypothesis of spontaneous generation of life, and yesterday her evidence was a step closer. In 2009, British scientist John Sutherland was able to offer a scheme in which “promobolan” could be synthesized cytosine and uracil, two of the four building blocks of RNA. Yesterday, the journal Science published a report that recreated the conditions of the Autonomous synthesis of adenine and guanine, or purine bases (purines).
Proteins could not give the beginning of life on our planet — they are not able to store and transmit information. DNA can store information but by itself is not viable: it can’t reproduce without assistance and are generally quite reluctant to react. Therefore, even in the 80-ies of XX century, scientists assumed that if life originated by itself, then it started with RNA molecules, which may enter into various reactions and store the genetic code.
It only remains to prove that RNA could be reproduced accidentally from the “primordial soup” — hot water and the first molecules based on carbon chains.
To synthesize the separate strands of RNA ribozymes in the lab learned quickly. Some great challenging task to obtain ribozymes with polymerase activity, that is, those strands of RNA that will be propagated to other ribozymes. The simplest of them, who was able to double short chains, were obtained in the early 2000s, and it was a huge breakthrough. Then biologists came to the conclusion that initially could exist two ways of lengthening, the complications of chain: replication of short RNA with ribozol with polymerase activity and through a simple “Assembly” of the individual nucleic bases: adenine, guanine, cytosine and uracil.
The chemical structure of RNA polinukleotid
Once all required for RNA synthesis processes were completed in the laboratory, it was necessary to make some more complicated thing, namely to prove experimentally that in the conditions of ancient Earth such a reaction could go by themselves. Today the big task of recreating biogenesis was one huge step closer to completion.
First karell and his colleagues noticed that formamidopyrimidine molecule that plays a role in repairing damaged DNA also reacts with the formation of purine. Then biologists began to pick up conditions that could develop on the Earth and which could be synthesized molecule purine.
The first stage required only hydrogen acid residues of hydrocyanic acid and water. It is believed that a simple triatomic hydrogen cyanide was very common on Earth in the period before the emergence of life. In water it readily reacts and gives aminopyrimidines wereexamined containing an amino group. This last is a very reactive substance that scientists have been rather bad — among the many products of their reactions, not all were desired purine.
It was necessary to leave only one of various amines. It turned out that it only takes a little bit to acidify the environment and acids on prehistoric Earth is also enough to able to react with other substances were only aminopyrimidine.
Last year, the Rosetta probe landed on comet Churyumov-Gerasimenko and took samples of the substance, which found formic acid and formamide. Both of these substances reacts with aminopyrimidines and some other substances in izobilii give purine.
Still not solved. For instance, there is this contradiction: the conditions necessary for synthesis of purines and pyrimidines, are slightly different, and for the formation of RNA and they both need to be in one place at one time. Still a lot of work, but each experimental confirmation increases the probability of biogenesis — and maybe, one day, a spontaneous generation of life will cease to seem to us an amazing, nearly impossible coincidence.
