News – Before life appeared on Earth, many of the physical processes on our planet were very chaotic. Plenty of small compounds, and polymers of various lengths, made up of substrates (such as the bases found in DNA and RNA), were present in all possible combinations. Before life-like chemical processes can emerge, the degree of disorder in these systems must be reduced. In a new study, LMU physicists led by Dieter Braun show that basic properties of simple polymers, combined with specific aspects of the prebiotic environment, can trigger selection processes that reduce disorder.
In previous publications, the Braun research group investigated how spatial order could be developed in narrow, waterlogged chambers within porous volcanic rocks on the seabed. These studies showed that, in the presence of temperature differences and a convective phenomenon known as the Soret effect, RNA strands could be collected locally by several orders of magnitude in a length-dependent manner. “The problem is that the basic layers of the longer molecules that a person gets are completely disordered,” Braun says.
Enhanced ribozymes (RNA-based enzymes) have a specific base layer that allows the molecules to fold into specific shapes, and most oligomers formed on Early Earth may have had random sequences. . “The total number of possible basic sequences, known as the ‘space sequence’, is enormous,” said Patrick Kudella, the first author of the new report. -the complex structures resembling action ribozymes or comparable molecules were collected by a random process only. ”This led the LMU team to suspect that the expansion of molecules was going to create larger‘ oligomers ’. depending on the type of selection method.
Since at the time of the Origin of Life there were only a few very simple physical and chemical processes compared to cell reproduction mechanisms, the selection of sequences must be based on the environment and characteristics of the oligomers. This is where Braun’s group research comes in. For the catalytic action and stability of oligomers, it is important that they form double strands as the well-known helical structure of DNA. This is a basic property with many polymers and enables complexing with both two-layer and single-layer. The single-row parts can be rebuilt by two processes. First, with so-called polymerization, in which strands are terminated with single centers to form complete double strands. The other has what is called ligation. In this process, oligomers go further together. Here, both two-layer and single-layer are formed, which enables further growth of the oligomer.
“Our test starts with a large number of short DNA strands, and in our model system for early oligomers we use only two support centers, adenine and thymine,” says Braun. ‘assuming that allowing strands with random sequences leads to the formation of longer strands, whose basal sequences are less chaotic. “Braun’s group then analyzed the given series combinations. in these tests using a method that is also used in the analysis of the human genome.The test confirmed that the entropy was sequential, ie the degree of disorder or randomization within of the series recovered, were reduced in these trials.
The researchers were also able to identify the causes of this ‘self-generated’ order. They found that most of the strains found fell into two classes – with a base of 70% adenine and 30% thymine, or vice versa. “With a much larger portion of one of the two bases, the ligament cannot fold on itself and remain as a reflex partner for the ligation,” Braun explains. Thus, almost any strands with half of each of the two bases are formed in the refraction. “We’ll also see how small splits in the combination of the short DNA pool leave out specific location-dependent motif patterns, especially in long product loops,” Braun says. research, because strands of just two different centers with a specific base ratio are limited ways to differentiate from each other. “Only specific algorithms find such remarkable detail,” says Annalena Salditt, co. -author of the study.
The experiments show that the simplest and most basic features of oligomers and their environment can be the basis for selective processes. Even in a simpler modeling system, different selection mechanisms can come into play, which affect the growth of strands at blades of different lengths, and are the result of a combination of factors. According to Braun, these selection tools were essential for the creation of catalytically active complexes such as ribozymes, and therefore played an important role in the emergence of life from chaos.
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