A estabilidade das bases de RNA: implicações para a origem da vida

The stability of the RNA bases: Implications for the origin of life

1. Matthew Levy and 
2. Stanley L. Miller*

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Author Affiliations

1. Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093-0506

1. Contributed by Stanley L. Miller

Abstract

High-temperature origin-of-life theories require that the components of the first genetic material are stable. We therefore have measured the half-lives for the decomposition of the nucleobases. They have been found to be short on the geologic time scale. At 100°C, the growth temperatures of the hyperthermophiles, the half-lives are too short to allow for the adequate accumulation of these compounds (t _1/2 for A and G ≈ 1 yr; U = 12 yr; C = 19 days). Therefore, unless the origin of life took place extremely rapidly (<100 yr), we conclude that a high-temperature origin of life may be possible, but it cannot involve adenine, uracil, guanine, or cytosine. The rates of hydrolysis at 100°C also suggest that an ocean-boiling asteroid impact would reset the prebiotic clock, requiring prebiotic synthetic processes to begin again. At 0°C, A, U, G, and T appear to be sufficiently stable (t _1/2 ≥ 10⁶ yr) to be involved in a low-temperature origin of life. However, the lack of stability of cytosine at 0°C (t _1/2 = 17,000 yr) raises the possibility that the GC base pair may not have been used in the first genetic material unless life arose quickly (<10⁶ yr) after a sterilization event. A two-letter code or an alternative base pair may have been used instead.

• nucleobase hydrolysis/RNA world/chemical evolution

Footnotes

• ↵ * To whom reprint requests should be addressed. e-mail:smiller@ucsd.edu. [Deceased/Falecido]
• Copyright © 1998, The National Academy of Sciences
• PDF gratuito deste artigo aqui.
NOTA DESTE BLOGGER: O Mysterium tremendum continua Mysterium tremendum, e o que temos sobre a origem da vida é nada mais do que meras especulações do tipo Abracadabra, Alakazam, Presto, Voilá la vie, como se isso fosse muito fácil de ser realizado, como tirar doce de criança. 
Atualmente, nós não temos uma teoria sobre a origem da vida, mas os livros didáticos aprovados pelo MEC/SEMTEC/PNLEM trazem os modelos arcaicos de Oparin e Miller como se fossem o supra sumo de modelos científicos quando na verdade já foram rejeitados pela comunidade científica há muito tempo.
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