| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2004: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2003: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
RNA world hypothesis is important as a principle of origin of life. However, there are some drawbacks from the viewpoint of hydrothermal origin of life. Since RNA is labile, it is unlikely that an RNA world system have emerged under the primitive earth conditions. However, there have been few studies carried out to evaluate this assumption. In this study, some primitive formation reactions of oligonucleotides were examined whether these models are possible to be used as primitive polymerase models under hydrothermal conditions. Moreover, the correlation between the RNA world systems and the chemical evolution of proteins were investigated on the basis of our recent theoretical works on the origin and evolution of life.
1.It is well known that the activated guanosine monomer, which is modified using imidazole on phospoate group of guanosine 5'-monophosphate, forms oligoguanylate in the presence of a polycytidylic acid template(TD reaction). The influence of thermal copolymers of amino ac
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id to the TD reaction was investigated. In addition, the influence of amino acids was also investigated. Conclusively, it was found that thermal copolymers including histidine and histidine itself inhibited the TD reaction.
2.Oligonucleotides which possess 5'-phosphate and 3'-hydroxyl terminals, are condensated to form cyclic oligonucleotides in the presence of water soluble carbodiimide. The rate constants of the cyclization reactions were determined at 0 - 75 ℃. According the kinetic analysis, the rate of the formation of phosphodiester bond could be greater than that of the hydrolysis of phosphodiester bond. Thus, it is strongly assumed that oligonucleotide could have been formed under the hydrothermal conditions on the primitive earth.
3.The elongation reactions of 11 - 16-mers oligonucleotides, which consist of cytosine and guanine and are possibly form hairpin structure, were investigated using water soluble carbodiimide. An HPLC method was investigated for the analysis of these reactions. It was confirmed that some elongations occurred under these reactions.
4.Based on the reaction behavior of formation and degradation of RNA under hydrothermal conditions, it was deduced that the formation of an RNA system consisting of entirely RNA molecules would have been impossible or difficult under hydrothermal environments on the primitive earth. This assumption is consistent with theoretical works on the origin of life. Then, possible formation models of protein-like molecules under hydrothermal conditions were investigated using our hydrothermal flow reactor system to link the RNA world and the RNA-protein world. Based on these studies, it was discovered that some oligopeptides form at 10-20 sec at 250-310 ℃. Less
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