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In 1924, Russian biochemist Alexander Oparin claimed that life on Earth was developing through gradual chemical changes of organic molecules, in the "primordial soup" that probably existed on Earth four billion years ago. According to him, the complex combination of lifeless molecules, combining forces in small oily droplets, could badume life faculties – self-replication, selection and evolution. Thirty years later, when the structure of DNA was deciphered, it was realized that this molecule was capable of self-replication, apparently solving the enigma of the origin of life without resorting with Oparin droplets. . But critics have argued that life requires not only replicators, but also enzymatic catalysts to control metabolism. Another 30 years has pbaded before the discovery that RNA, a key element in transferring DNA information to proteins, can also be an enzyme. This is how the concept of "RNA World" was born, where life began when the primordial soup gave birth to a ribozyme, able to both replicate and control the metabolism.
Despite these doubts, a replicating ribosome is very complex. molecule, with negligible probability of spontaneous appearance in the soup. This has led to an alternative concept – mutually catalytic networks, allowing the copy of entire molecular sets. This idea echoes the evolutionary combination of simple Oparin molecules, each with a high probability of occurrence in the soup. What was left was to generate a detailed chemical model that will help support such a narrative.
Prof. Doron Lancet and colleagues at the Weizmann Institute of Science, Department of Molecular Genetics, have proposed such a model. First of all, it was necessary to identify the type of appropriate molecules, which can accrete together and effectively form networks of mutual interactions, in line with the droplets. Oparin. Lancet proposed lipids, oily compounds that spontaneously form aggregated membranes surrounding all living cells. Lipid bubbles (vesicles) can grow and divide like living cells. This is how Lancet created the concept "Lipid World" twenty years ago.
To badyze invoked molecular networks, they used systemic biology and computational chemistry tools that instill rigor in the concept of mutually catalytic networks.
They discuss in detail the nagging question of how lipid bademblages can store and transmit information from one growth-split generation to another. They come with a notion so far rarely explored that what is spreading is compositional information, and shows by detailed computer simulations how this is happening. In addition, they indicate a profound similarity of this composition by copying how growing and proliferating living cells retain their epigenetic information, which is independent of DNA replication.
In an article published in Journal of the Royal Society Interface Lancet and colleagues report a large literature study, showing that lipids can exert enzymatic catalysis, similar to ribozymes. This is a crucial property for forming networks of mutual interaction. Subsequently, the authors show, using the tools of systems biology and computational chemistry, that oily droplets can accumulate and store compositional information and, when they undergo fission, transmit the same information. information to offspring
. Scientists have demonstrated that specific lipid compositions, called "composomes," can undergo compositional mutations, be subject to natural selection in response to environmental changes and even undergo Darwinian selection. Professor Lancet comments that such an information system, which relies on compositions and not on the sequence of chemical "letters" as in DNA, recalls the field of epigenetics, where the characters are inherited regardless of the DNA sequence. This accredits the scientists' hypothesis that life could emerge before the advent of DNA and RNA. In their article, they actually define a chemical path that leads to the appearance of genetic material in the context of oily droplets.
The concept of Lancet's "lipid world" depends on the question of whether there was enough water. hate "molecules in the primordial soup." Here again, scientists describe a comprehensive literature search that suggests there is a high probability that such molecules are present on the early Earth, a finding that has been reinforced by a very recent study showing that Enceladus, one of Saturn's moons, has a sub-glacial ocean (primordial ocean) filled with "water-hating" compounds, some of which could form Lipid World-type droplets. argues that these results, as well as calculations based on innovative models, show that the probability of emergence of life is relatively high, including the exciting possibility that Enceladus is currently home to some life-based forms of life. early lipids
