|M.Sc Student||Katz Dana|
|Subject||Composite Particles as Catalytic Substrates for|
Non-Enzymatic Synthesis of Nucleotides from
|Department||Department of Chemical Engineering||Supervisor||Professor Yaron Paz|
|Full Thesis text|
The origin of life is one of the most fundamental enigmas that the human mind has been studying for many years. Among the leading theories is the RNA world hypothesis, suggesting that life originated as a system of self- replicating catalytic RNA.
Titanium dioxide is capable of catalyzing the formation of nucleic bases from formamide. In parallel, the presence of Calcium ions or Magnesium ions can direct the formose reaction forming sugars from formaldehyde to yield ribose. Accordingly, it can be hypothesized that Hydromagnesite, a basic magnesium carbonate natural mineral, may provide the necessary conditions for ribose formation.
We present hereby a new approach that combines composite particles as a mean to form RNA from pre-biotic substances. According to this approach the nucleic bases are formed on one domain of the particles. The ribose is formed at another domain and the two react together with phosphates to form nucleic acids at the contour line between the domains. This scenario allows generating high concentration of each component within short distance. Moreover, it allows for sequential formation under different conditions, provided that the products of each step adsorb on the surface of the composite particle.
To study this approach, composite particles containing titanium dioxide and hydromagnesite were prepared and characterized. The adsorption of nucleic bases, ribose, Adenosine-5'-triphosphate and phosphoric acid on titanium dioxide, hydromagnesite, the composite particles and magnesium hydroxide was measured by FTIR and UV-Vis spectroscopy. It was found that nucleic bases do adsorb on the surface of titanium dioxide, hydromagnesite and on the composite particles, while ribose molecules were not adsorbed on none of these substrates, even at low temperatures.
Borate ions are known for stabilizing ribose molecules. It was shown by us that boric acid molecules do adsorb on the surface of magnesium hydroxide, but no indications of ribose adsorption on the pre-adsorbed borate were found. In addition, the possibility that ribose could have been adsorbed from a formaldehyde-water solution had to be studied. Similarly to the previous case, no indications for the adsorption of ribose on hydromagnesite and Mg(OH)2 were observed.
The fact that ribose does not adsorb on the surface poses a severe challenge to the hypothesized mechanism. There are several ways to detour this problem, for example, the formation of a phosphateribose complex. While we cannot report on solving this difficult enigma, this work still provides valuable conclusions that may be relevant in future studies.