Pose climatisation cenon2/1/2024 Others start with chemistry and find synthetic reactions and pathways that result in greater chemical complexity that synthesize the building blocks of the macromolecules that constitute life, such as DNA, RNA, proteins, and lipids. Some start with biology and investigate how extant metabolic pathways may have come to fruition, concentrating on bacterial and archaeal life that most closely resembles the last universal common ancestor. The starting points for origins of life research are diverse and researchers do not agree about the best place to begin. This suggests the plausibility of the photoproduction of purine deoxyribonucleotides, such as the photoproduction of simple sugars, proceeds more efficiently in the presence of bisulfite. The photoreduction of thioanhydroadenosine with bisulfite produced 2′-deoxyriboadenosine (dA) on the timescale of days. The photoreduction of thioanhydrouridine with hydrogen sulfide did not succeed even after a long period of irradiation, providing a lower limit on the timescale of several years. The photoanomerization of α-thiocytidine would take months to complete, and the production of oxidation products from hydroxyl radicals would take years. We predict that hypophosphite oxidation, HCN reduction, and photoproduction of nitroprusside would all operate on the surface of early Earth in a matter of days to weeks. We compare the output of StarLab to the light of the faint young Sun to constrain the timescales over which these reactions would occur on the surface of early Earth. We then attempt a series of reactions testing different aspects of a prebiotic chemical scenario involving hydrogen cyanide (HCN), sulfites, and sulfides under the UV light of StarLab, including hypophosphite oxidation by UV light and hydrogen sulfide, photoreduction of HCN with bisulfite, the photoanomerization of α-thiocytidine, the production of a chemical precursor of a potentially prebiotic activating agent (nitroprusside), the photoreduction of thioanhydrouridine and thioanhydroadenosine, and the oxidation of ethanol (EtOH) by photochemically generated hydroxyl radicals. We construct a solar simulator for the UV light of the faint young Sun on the surface of early Earth, called StarLab. Here we experimentally investigate whether the UV flux available on the surface of early Earth, given a favorable atmosphere, can facilitate a variety of prebiotic chemical syntheses. Ultraviolet (UV) light has long been invoked as a source of energy for prebiotic chemical synthesis, but experimental support does not involve sources of UV light that look like the young Sun.
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