Chemists find a recipe that may have jump-started life on Earth [View all]

[muriel_volestrangler]

How to produce the RNA bases from very simple chemicals:

Those building blocks—cytosine, uracil, adenine, and guanine—have previously been re-created in the lab from other starting materials. In 2009, chemists led by John Sutherland at the University of Cambridge in the United Kingdom devised a set of five compounds likely present on early Earth that could give rise to cytosine and uracil, collectively known as pyrimidines. Then, 2 years ago, researchers led by Thomas Carell, a chemist at Ludwig Maximilian University in Munich, Germany, reported that his team had an equally easy way to form adenine and guanine, the building blocks known as purines. But the two sets of chemical reactions were different. No one knew how the conditions for making both pairs of building blocks could have occurred in the same place at the same time.
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Carell’s story starts with only six molecular building blocks—oxygen, nitrogen, methane, ammonia, water, and hydrogen cyanide, all of which would have been present on early Earth. Other research groups had shown that these molecules could react to form somewhat more complex compounds than the ones Carell used.

To make the pyrimidines, Carell started with compounds called cyanoacetylene and hydroxylamine, which react to form compounds called amino-isoxazoles. These, in turn, react with another simple molecule, urea, to form compounds that then react with a sugar called ribose to make one last set of intermediate compounds.

Finally, in the presence of sulfur-containing compounds called thiols and trace amounts of iron or nickel salts, these intermediates transform into the pyrimidines cytosine and uracil. As a bonus, this last reaction is triggered when the metals in the salts harbor extra positive charges, which is precisely what occurs in the final step in a similar molecular cascade that produces the purines, adenine and guanine. Even better, the step that leads to all four nucleotides works in one pot, Carell says, offering for the first time a plausible explanation of how all of RNA’s building blocks could have arisen side by side.

https://www.sciencemag.org/news/2018/10/chemists-find-recipe-may-have-jump-started-life-earth