Peptides on Stardust May Have Provided a Shortcut to Life

Billions of years ago, an unknown location on the primordial Earth became a cauldron of complex organic molecule from which the first cells emerged. Origin-of-life researchers have proposed a lot of different ideas about how that happened. The most difficult to account for are the proteins, which are made by living cells. How did the first protein form?

Scientists have been looking at Earth. A new discovery suggests that the answer could be found inside dark clouds.

A group of Astrobiologists showed last month in Nature Astronomy that there is a way to form a molecule on the frozen particles of the universe. Some of the starting materials for life could have come from comets and meteorites, as well as other worlds.

Serge Krasnokutski, the lead author on the new paper and a researcher, said that the new space-based mechanism for forming peptides is more promising than the chemical processes that could have occurred on a lifeless Earth. He said that the simplicity suggests that the first molecule involved in the evolutionary process leading to life was the proteins.

It's very much an open question whether those peptides could have contributed meaningfully to the origin of life. The chemistry demonstrated in the new paper is very cool, but it doesn't bridge the phenomenal, said Paul Falkowski, a professor at the School of Environmental and Biological Sciences at Rutgers University.

The finding by Krasnokutski and his colleagues shows that there is more to the universe than scientists thought.

Dust in a vacuum.

Cells make it easy to make something. They manufacture both peptides and proteins extravagantly, because of the environments rich in useful molecules like amino acids and their own stockpiles of genetic instructions and catalytic enzymes.

There wasn't an easy way to do it on Earth before cells existed. The production of peptides is an inefficient two-step process that involves first making and then removing water, and then linking up the two chains in a process called polymerization. Both steps have a high energy barrier, so they only occur if large amounts of energy are available to kick-start the reaction.

Because of these requirements, most theories about the origin of proteins have focused on scenarios in extreme environments, such as near the ocean floor, or assumed the presence of molecules with catalytic properties that could lower the energy barrier enough to push the reactions forward. The most popular origin-of-life theory proposes that the first molecule in life wasRNA. Krasnokutski says that special conditions would need to be met to concentrate the amino acids. It isn't clear how and where those conditions could have arisen on the primordial Earth.