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Characterization of RNA-Like Oligomers from Lipid-Assisted Nonenzymatic Synthesis: Implications for Origin of Informational Molecules on Early Earth.

Mungi CV, Rajamani S - Life (Basel) (2015)

Bottom Line: The resultant products were characterized to understand their chemical makeup.Formation of such oligomers would have permitted sampling of a large variety of bases on a preformed polymer backbone, resulting in "prebiotic phosphodiester polymers" prior to the emergence of modern RNA-like molecules.This suggests that primitive genetic polymers could have utilized bases that conferred greater N-glycosyl bond stability, a feature crucial for information propagation in low pH and high temperature regimes of early Earth.

View Article: PubMed Central - PubMed

Affiliation: Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India. cvmungi@students.iiserpune.ac.in.

ABSTRACT
Prebiotic polymerization had to be a nonenzymatic, chemically driven process. These processes would have been particularly favored in scenarios which push reaction regimes far from equilibrium. Dehydration-rehydration (DH-RH) cycles are one such regime thought to have been prevalent on prebiotic Earth in niches like volcanic geothermal pools. The present study defines the optimum DH-RH reaction conditions for lipid-assisted polymerization of nucleotides. The resultant products were characterized to understand their chemical makeup. Primarily, our study demonstrates that the resultant RNA-like oligomers have abasic sites, which means these oligomers lack information-carrying capability because of losing most of their bases during the reaction process. This results from low pH and high temperature conditions, which, importantly, also allows the formation of sugar-phosphate oligomers when ribose 5'-monophosphates are used as the starting monomers instead. Formation of such oligomers would have permitted sampling of a large variety of bases on a preformed polymer backbone, resulting in "prebiotic phosphodiester polymers" prior to the emergence of modern RNA-like molecules. This suggests that primitive genetic polymers could have utilized bases that conferred greater N-glycosyl bond stability, a feature crucial for information propagation in low pH and high temperature regimes of early Earth.

No MeSH data available.


Graphical representation of HPLC chromatograms obtained from Cyc7 samples of DH-RH reactions of 5'-AMP (5 mM) and POPC (1 mM) performed at various temperatures (as indicated) at pH 2. The areas under relevant HPLC peaks are used as a proxy for comparing peak abundance observed in the different reactions. Higher temperatures (90 and 105 °C) promoted better polymerization but were also accompanied by greater breakdown.
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life-05-00065-f004: Graphical representation of HPLC chromatograms obtained from Cyc7 samples of DH-RH reactions of 5'-AMP (5 mM) and POPC (1 mM) performed at various temperatures (as indicated) at pH 2. The areas under relevant HPLC peaks are used as a proxy for comparing peak abundance observed in the different reactions. Higher temperatures (90 and 105 °C) promoted better polymerization but were also accompanied by greater breakdown.

Mentions: At 60 °C, less polymerization was observed, which increased over cycles; a similar trend was also observed for the 75 °C reaction. In both cases, breakdown was less but so was the extent of polymerization. The cycling reaction that was carried out at 90 °C resulted in greater yields of oligomers even at lower cycles, which further improved with an increasing number of DH-RH cycles. However, at an even higher temperature of 105 °C, although polymerization was observed, oligomer yields did not alter much with subsequent cycles and the breakdown observed was also considerably high. On comparing reactions that were carried out for seven cycles at various temperatures (Figure 4), it was observed that higher temperatures promoted better polymerization, but this was also accompanied by greater breakdown (as seen in 105 °C reaction). Given our observations, it seems that temperatures of 80–90 °C are optimal for carrying out multiple DH-RH cycles.


Characterization of RNA-Like Oligomers from Lipid-Assisted Nonenzymatic Synthesis: Implications for Origin of Informational Molecules on Early Earth.

Mungi CV, Rajamani S - Life (Basel) (2015)

Graphical representation of HPLC chromatograms obtained from Cyc7 samples of DH-RH reactions of 5'-AMP (5 mM) and POPC (1 mM) performed at various temperatures (as indicated) at pH 2. The areas under relevant HPLC peaks are used as a proxy for comparing peak abundance observed in the different reactions. Higher temperatures (90 and 105 °C) promoted better polymerization but were also accompanied by greater breakdown.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390841&req=5

life-05-00065-f004: Graphical representation of HPLC chromatograms obtained from Cyc7 samples of DH-RH reactions of 5'-AMP (5 mM) and POPC (1 mM) performed at various temperatures (as indicated) at pH 2. The areas under relevant HPLC peaks are used as a proxy for comparing peak abundance observed in the different reactions. Higher temperatures (90 and 105 °C) promoted better polymerization but were also accompanied by greater breakdown.
Mentions: At 60 °C, less polymerization was observed, which increased over cycles; a similar trend was also observed for the 75 °C reaction. In both cases, breakdown was less but so was the extent of polymerization. The cycling reaction that was carried out at 90 °C resulted in greater yields of oligomers even at lower cycles, which further improved with an increasing number of DH-RH cycles. However, at an even higher temperature of 105 °C, although polymerization was observed, oligomer yields did not alter much with subsequent cycles and the breakdown observed was also considerably high. On comparing reactions that were carried out for seven cycles at various temperatures (Figure 4), it was observed that higher temperatures promoted better polymerization, but this was also accompanied by greater breakdown (as seen in 105 °C reaction). Given our observations, it seems that temperatures of 80–90 °C are optimal for carrying out multiple DH-RH cycles.

Bottom Line: The resultant products were characterized to understand their chemical makeup.Formation of such oligomers would have permitted sampling of a large variety of bases on a preformed polymer backbone, resulting in "prebiotic phosphodiester polymers" prior to the emergence of modern RNA-like molecules.This suggests that primitive genetic polymers could have utilized bases that conferred greater N-glycosyl bond stability, a feature crucial for information propagation in low pH and high temperature regimes of early Earth.

View Article: PubMed Central - PubMed

Affiliation: Indian Institute of Science Education and Research (IISER), Pune, Maharashtra 411008, India. cvmungi@students.iiserpune.ac.in.

ABSTRACT
Prebiotic polymerization had to be a nonenzymatic, chemically driven process. These processes would have been particularly favored in scenarios which push reaction regimes far from equilibrium. Dehydration-rehydration (DH-RH) cycles are one such regime thought to have been prevalent on prebiotic Earth in niches like volcanic geothermal pools. The present study defines the optimum DH-RH reaction conditions for lipid-assisted polymerization of nucleotides. The resultant products were characterized to understand their chemical makeup. Primarily, our study demonstrates that the resultant RNA-like oligomers have abasic sites, which means these oligomers lack information-carrying capability because of losing most of their bases during the reaction process. This results from low pH and high temperature conditions, which, importantly, also allows the formation of sugar-phosphate oligomers when ribose 5'-monophosphates are used as the starting monomers instead. Formation of such oligomers would have permitted sampling of a large variety of bases on a preformed polymer backbone, resulting in "prebiotic phosphodiester polymers" prior to the emergence of modern RNA-like molecules. This suggests that primitive genetic polymers could have utilized bases that conferred greater N-glycosyl bond stability, a feature crucial for information propagation in low pH and high temperature regimes of early Earth.

No MeSH data available.