- Noncanonical RNA Nucleosides as Molecular Fossils of an Early Earth—Generation by Prebiotic Methylations and Carbamoylations
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The RNA-world hypothesis assumes that life on Earth started with small RNA molecules that catalyzed their own formation. Vital to this hypothesis is the need for prebiotic routes towards RNA. Contemporary RNA, however, is not only constructed from the four canonical nucleobases (A, C, G, and U), it also contains many chemically modified (noncanonical) bases. A still open question is whether these noncanonical bases were formed in parallel to the canonical bases (chemical origin) or later, when life demanded higher functional diversity (biological origin). Here we show that isocyanates in combination with sodium nitrite establish methylating and carbamoylating reactivity compatible with early Earth conditions. These reactions lead to the formation of methylated and amino acid modified nucleosides that are still extant. Our data provide a plausible scenario for the chemical origin of certain noncanonical bases, which suggests that they are fossils of an early Earth.
- Schneider, Christina,Becker, Sidney,Okamura, Hidenori,Crisp, Antony,Amatov, Tynchtyk,Stadlmeier, Michael,Carell, Thomas
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supporting information
p. 5943 - 5946
(2018/04/30)
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- Methylation study of ribonucleosides, deoxyribonucleosides, and 2′-O-methylribonucleosides with trimethylsulphonium hydroxide and trimethylsulphonium iodide. Influence of the 2′-hydroxy-groups on the reactivity of the base moieties of ribonucleosides
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Methylations of the naturally occuring ribonucleoside (1), deoxyribonucleoside (2), and 2′-O-methylribonucleoside (3) were carried out using trimethylsulphonium hydroxide (Me3SOH) and trimethylsulphonium iodide (Me3Sl). The base moiety of (2) and (3) are more reactive than the corresponding base moiety of (1). The sites and extent of methylation of (2) are considerably different from those of (1), but are almost identical with those of (3). The reactivities of (1)-(3) are discussed in connection to an intramolecular interaction of the 2′-OH groups with the base moiety of (1). The methylating characteristics of Me 3SOH and Me3Sl are also described. The kinetics indicate an SN2 mechanism for methylation of nucleosides by Me 3S+ ions.
- Yamauchi, Kiyoshi,Nakagima, Toru,Kinoshita, Masayoshi
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p. 2787 - 2792
(2007/10/02)
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