15:30 〜 15:45
[MIS02-05] Effects of borate on sugar phosphorylation in the evaporitic environment on early Earth.
キーワード：ホウ酸、リン酸、ヌクレオチド、リボースリン酸
In the evolution from organic molecules to life, one of the most essential steps has been regarded as the emergence of RNAs, molecules that can act as biocatalysts and hold a part of gene information. RNAs are polymers of ribonucleotides which are consisted of ribose, nucleobase, and phosphate. Most of the previous research attempted to synthesize nucleotides by phosphorylation of nucleosides. Nucleoside synthesis by this approach is chemically possible, but might not have been possible geologically since this reaction’s source materials are substantially unstable in aqueous environments. Thus, it is not clear whether nucleotides were formed from nucleoside phosphorylation on the early Earth. Current life synthesizes nucleotides from ribose 5’-phosphate and nucleobase in their cell. This motivated us to investigate the phosphorylation of ribose as the similar pathway to the biosynthesis. This reaction was investigated previously and found that it does not happen, due to the selective formation of ribose 1’-phosphate. In this study, the phosphorylation of ribose was investigated in the presence of borate and urea because borate forms a complex with ribose and stabilize it and urea catalyzes the phosphorylation of hydroxyl. Since the phosphorylation of sugars is a dehydration reaction, the dry condition is thermodynamically advantageous. Sample drying was carried out in a furnace at 80℃ for 24 hours. Orthoboric acid was used as the borate source, and disodium phosphate was used as the phosphate source. As a result of liquid chromatography-mass spectrometry of the experimental products, ribose 5’-phosphate was detected with high intensities in the samples containing borate, whereas they were detected with very low intensities in the samples without borate. The extent of the phosphorylation was the most significant with ribose compared with other aldopentoses. These results suggest that ribose 5’-phosphate was preferentially formed in borate-rich evaporitic environments on the early Earth leading to further chemical evolution to RNA.