It turns out that heated rocks may have been key to life on Earth. Scientists have found that temperature gradients within pores in rock would have helped separate primitive biopolymers on the bases of their sequences.

When life first arose on Earth, it had to undergo several different processes. More specifically, it likely involved selective interactions between simple probiotic molecules that allowed them to form progressively more complex chemical structures. The structures eventually started to store genetic information and began to replicate.

The most likely lifeforms that were first present on Earth are polymeric molecules. These were made up of subunits called ribonucleotides. Now, scientists are studying how ribonucleotides and other precursor molecules could have accumulated in concentrations high enough where they could interact.

In earlier experiments, researchers showed that temperature differences in tiny water-filled channels, such as those found at hydrothermal vents, can partition DNA molecules based on their lengths.

In this latest study, the researchers continued to focus on how rocks may have separated "good" molecules from "bad." They used glass capillary tubes filled with an aqueous solution containing mixtures of two DNA fragments with slightly different nucleotide sequences. Then, the researchers heated the pores on one side to generate a gradient of about 17 degrees Celsius within the capillary. Afterwards, the researchers analyzed the distribution of DNA molecules.

"The separation is so effective that certain types of fragments actually condense into gels when they hybridize with complementary partner molecules," said Christof Mast, one of the researchers involved in the new study from LMU in Munich. "Even more strikingly, sequences that differ by only a few bases are partitioned into different gels."

This particular degree of specificity was a surprise. It's likely that the temperature gradient within the pores is what makes the crucial difference. In other words, temperature-driven sorting may have been an important mechanism for the partitioning and concentration of biomolecules that could readily interact with each other. It's likely that this interaction allowed them to form longer and longer polymer chains. This, in turn, is an important prerequisite for the origin of life.

The findings were published in the April 6 issue of the journal Angewandte Chemie.

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