Researchers from the University of Pennsylvania have developed a chemical model that can simulate how cells were formed four billion years ago. Using "macromolecules" called polymers, scientists have created the original cell-like structure of fused RNA-RNA is considered to be the genetic material on earth before DNA appeared, and this research also shows this molecule How chemical reactions take place in the early possible earth environment. The research results were published in the Nature Chemistry magazine under Nature Press. (The picture shows that RNA strands (blue) and RNases (red) are grouped together in dextran droplets. Scientists at Penn University found that this division helps to catalyze chemical reactions. Modern biology believes that all life, except some viruses, uses DNA as a genetic storage material. According to the "RNA World" hypothesis, RNA first appeared on the earth. This kind of molecule can be used as a genetic storage material, or it can be used to catalyze chemical reactions, and then DNA and proteins. The latter two evolved much later. Unlike DNA, RNA has many different molecular conformations, so it can interact at the molecular level. In the latest article, two professors, Christine Keating and Philip Bevilacqua, and two graduate students, Christopher Strulson and Rosalynn Molden, explored this. A mystery repeatedly studied in the RNA world hypothesis. "The missing piece in the RNA world hypothesis puzzle is compartmentalization," Bevilacqua said. "Just appearing RNA molecules floating around is not enough. It is also necessary to divide these molecules functionally and ensure that they can stay together. This kind of packaging needs to be carried out in a small enough space-this is like a modern cell, the reason is simple: chemical reactions require various molecules to find each other and react. " To examine how early cell-like structures were formed and how RNA molecules were divided in the absence of the lipid molecules that modern cells possess, Strulson and Molden constructed a simple, non-living model "cell" in the laboratory, "Our research team used two kinds of polymers: polyethylene glycol (PEG) and dextran solutions to build spaces," Keating explained. "These solutions form different polymer-enriched spatial structures, helping RNA like The molecules of the class are locally concentrated. " The team members found that once RNA was encapsulated in a dextran-rich space structure, RNA molecules could be physically connected, and a chemical reaction took place. "Interestingly, the denser the RNA, the faster the reaction occurs," explains Bevilacqua. "We found that the chemical reaction rate can be as high as about 70 times. The most important thing is that RNA" what "can be strictly divided Just like a cell, our experiments with the Two-Phase Aqueous System (ATPS) have shown that some partitioning mechanisms may play a catalytic role in the early Earth environment. " Although this is not to say that polyethylene glycol and dextran were the special polymers that existed on the early Earth, this study proposed a reasonable route for phase separation—phase separation. When different types of polymers occur, phase separation will occur. These samples will not mix, but form two different liquids, similar to oil and water. "Keating said," We only found that using dextran and PEG The water phase space can promote biochemical reactions by increasing the concentration of local reactants, so there may be other types of polymers to promote the division of the early earth, "Strulson added." In addition to the RNA world hypothesis, these results may also be related to modern biology. The RNA localization of the membrane space in Central Africa is related to function. " The researchers also found that the longer the RNA strand, the higher the concentration of RNA wrapped in the ATPS space of the two-phase system, and the shorter RNA strand was excluded. "We speculate that this may indicate some original sorting method," Bevilacqua said. As the RNA becomes shorter, its enzyme activity also decreases. Therefore, in the early Earth system similar to the dextran-PEG model, full-length, functional RNA was sorted and sorted, concentrated into a phase, and Short RNA not only has fewer functions, but it may also inhibit important chemical reactions, so it is not included in this phase. " In the next step, researchers will verify this model with other polymers, Keating said, "We are interested in polymer systems that are closer to the existence of early Earth, hoping to understand the events that occur in space biology, where RNA partitioning participates in a variety of Biological processes. "
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