How guanine, one of the four building blocks of RNA, came to exist has long been a mystery. The answer, research finds, may be ultraviolet light.
- UV light might have triggered Earth's chemistry into forming the building blocks for biology.
- Early Earth had little atmosphere to block solar UV rays.
- Research is ongoing to mimic day/night cycles and to add minerals to see what else brews in an RNA stew.
In a quest to understand how life began on Earth, scientists have discovered that a blast of ultraviolet light may have been the spoon that stirred the simmering primordial soup.
The research demonstrates a more commonplace scenario for creating RNA -- believed to be an early coding system for life. And that opens a wider door for life's evolution not only on Earth, but possibly elsewhere in the solar system and beyond.
Researchers at Georgia Tech and the University of Roma "La Sapienza" focused on the molecule formamide, the simplest structure containing the required four building blocks of life -- carbon, hydrogen, oxygen and nitrogen.
Previous studies have already shown how heating formamide in a mineral stew creates most of the ingredients for ribonucleic acid, commonly known as RNA. RNA is thought to have served as an early operating system for life, later joined by the more robust deoxyribonucleic acid, or DNA, genetic coder.
Missing from the formamide brew, however, has been guanine, one of RNA's four critical ingredients. (The others are adenine, cytosine and uracil.) One lightning rod for guanine's creation, scientists discovered, is ultraviolet light.
"A lot of things can happen when you put a photon into the mix," Georgia Tech physicist Thomas Orlando told Discovery News.
Today, Earth's atmosphere blocks most UV rays from the sun, but in its early years the planet lacked ozone and other shielding chemicals in its skies.
The research demonstrates a scenario for creating RNA that would not require lots of heat or standing pools of liquid water. The finding could also mean conditions for life elsewhere in the solar system may not be as stringent.
"You don't have to have incredibly special conditions," Orlando said. "A lot of people have prebiotic chemistry scenarios that are aqueous-based. In this way, water is important, but not as important as formamide. That's a big change."
Scientists are now working to mimic the day-night cycles of solar ultraviolet radiation and adding different minerals to see how that changes the resulting RNA brew.
"What we're looking for is the chemistry that gives us the building blocks for life," said Nicholas Hud, head of Georgia Tech's Center for Chemical Evolution. "This is a very significant step."
The findings are reported in this week's issue of ChemBioChem.