RNA dimer synthesis using montmorillonite as a catalyst: The role of surface layer charge

The oligomerisation of activated nucleotides to form RNA is catalyzed by montmorillonite. However, the mechanism of this process and its use as a model for similar prebiotic chemistry is still under investigation. To date, amongst the more than two hundred clay minerals investigated as catalysts, only a few are excellent. We turned our attention to the less efficient catalysts to see how they performed in the synthesis of nucleotide dimers in which a nucleoside and an activated nucleotide produced only linear products of the form MpN. We have found that representative clay minerals, Otay and Chambers specifically, although poor at catalyzing the direct oligomerization of activated nucleotides, are able to promote these dimer syntheses. Sixteen reactions and thirty two products have been studied and found to vary in their outcome. The yields of 2′–5′ and 3′–5′-products were always less than those obtained with the excellent catalyst Volclay®. The results of this research provide a basis for further understanding of the physical processes in the mechanism of this catalysis and suggest that more clay minerals than hitherto expected may have the ability to catalyze RNA synthesis at the dimer level. These results have an important bearing upon the RNA world scenario for the origin of life.