Survival of the fittest before the beginning of life: selection of the first oligonucleotide-like polymers by UV light
1 Division of Biophysics, Department of Biology and Chemistry, Universität Osnabrück, D-49069 Osnabrück, Germany
2 A.N.Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow, 119899, Russia
3 Institute of Electrochemistry, Russian Academy of Sciences, Leninskii prosp. 31, 117071 Moscow, Russia
4 National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
BMC Evolutionary Biology 2003, 3:12 doi:10.1186/1471-2148-3-12Published: 28 May 2003
A key event in the origin of life on this planet has been formation of self-replicating RNA-type molecules, which were complex enough to undergo a Darwinian-type evolution (origin of the "RNA world"). However, so far there has been no explanation of how the first RNA-like biopolymers could originate and survive on the primordial Earth.
As condensation of sugar phosphates and nitrogenous bases is thermodynamically unfavorable, these compounds, if ever formed, should have undergone rapid hydrolysis. Thus, formation of oligonucleotide-like structures could have happened only if and when these structures had some selective advantage over simpler compounds. It is well known that nitrogenous bases are powerful quenchers of UV quanta and effectively protect the pentose-phosphate backbones of RNA and DNA from UV cleavage. To check if such a protection could play a role in abiogenic evolution on the primordial Earth (in the absence of the UV-protecting ozone layer), we simulated, by using Monte Carlo approach, the formation of the first oligonucleotides under continuous UV illumination. The simulations confirmed that UV irradiation could have worked as a selective factor leading to a relative enrichment of the system in longer sugar-phosphate polymers carrying nitrogenous bases as UV-protectors. Partial funneling of the UV energy into the condensation reactions could provide a further boost for the oligomerization.
These results suggest that accumulation of the first polynucleotides could be explained by their abiogenic selection as the most UV-resistant biopolymers.