Rock crevices are said to have fed proto-life

A great chemical mystery lies at the origin of life. Once upon a time, the precursors of today's complex biomolecules arose from simple molecules in chemical reactions. But how did exactly those building blocks from which the ancestors of proteins and nucleic acids were able to develop come together again and again from the vast variety of chemical substances? A team led by Christof B. Mast from LMU Munich has now proposed a mechanism that has repeatedly accumulated similar substances under similar conditions over millions of years. As the team reports in the scientific journal Nature, temperature differences in cracks and fissures in rocks can sort the building blocks of life. Such fissure systems are also being discussed as the origin of life.

The precursors of RNA, DNA and proteins must have repeatedly formed from similar molecules in roughly the same way over millions of years in order to eventually give rise to the first protoorganisms. And long afterwards, the necessary building blocks must have continued to accumulate so that the chemistry at the origin of life did not break down. This stable supply of specific building blocks over millions of years is difficult to explain - experts have proposed dozens of possible mechanisms, all with their own advantages and disadvantages.

Mast's team has now shown that even small temperature differences are sufficient for the building blocks of life to sort themselves differently in crevice systems. In an experiment, they showed that two chemically similar substances accumulate in different areas of a thin tube if one side of the tube is 15 degrees Celsius warmer than the other. On the one hand, liquid rises on the warm side and sinks on the cold side, and on the other hand, the molecules are driven away from the warm wall to different degrees. The second process is known as thermophoresis. Together, these two processes result in the molecules remaining in the upflow for different lengths of time and being enriched to different degrees at the ends of the tube.

In order to show that a network of such water-filled gaps can sort building blocks of life, the team constructed a system of three cavities that was 16 degrees warmer on one side than on the other. The experiments with building blocks of proteins, RNA and DNA show that substances arrange themselves spatially differently there. It also showed that the effect enriches the reactive molecule trimetaphosphate enough to drive a reaction between amino acids. The advantage of Mast's team's hypothesis is that water-filled rock crevices were present everywhere on the young Earth, and so the accumulation of substances could take place in a similar way over millions of years - wherever a heat source was nearby. This explains why there were areas with stable conditions and a constant supply of substances for a very long time. Complex and later animate chemical systems could develop there.

Spectrum of Science

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