Abiotic Synthesis of Substances Relative to the Origin of Life under the Oxidizing Atomosphere

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One of the objects of the investigation of "origin of life" is the estimation of the atomosphere of the primitive earth where living organisms were born. In the present work, it has been demonstrated that amino acids and nucleic acid bases can be synthesized from anaqueous solution containing both of CO_2 and NH_3 or ammonium carbonate by the irradiation of UV-light of wave length shorter than 280 nm at a temperature higher than 80ﾟC.This finding suggests that the abiotic synthesis of substances relative to the origin of life can be attained notonly under the reducing atomosphere composed of CH_4 and H_2 but also under the oxidizing atomosphere composed of CO_2 and O_2. Since the synthesis was found to be promoted remarkably by the addition of Mg^<2+> into the aqueous solution, the view can be drawn that the life was originated in the sea water, the aqueous salt solution. High concentrations of ammonuim oxalate and oxamic acid were found in the UV-irradiated solution, and hence these compounds were considered to be the possible intermediates in the photosynthesis. On the basis of the detailed investigation on the relation between the synthetic conditions and the yields of amino acids or nucleic acid bases and the effect of the coexistence of Mg^<2+> or the intermediates, the mechanism for the photosyntesis was elucidated as follows ; (1) The UV-irradiation of the aqueous ammonium carbonate solution produces ammonium oxalate. (2) Ammonium oxalate thus produced decomposes thermally resulting oxamic acid. Here, because of the strong complex formation between Mg^<2+> and oxamic acid, coexistence of Mg^<2+> promotes the thermal decomposition to oxamic acid and depresses the further decomposition of oxamic acid. (3) Oxamic acidproduces amino acids and nucleic acid bases absorbing UV-light of wave length shorter than 280 nm. (4) Relatives of saccharides might be synthesized from the intermediates such as oxalic