The role of montmorillonite in its catalysis of RNA synthesis

Montmorillonite catalyzes the oligomerization of activated nucleotides to form RNA. However, the mechanism of the montmorillonite catalysis, used as a model for similar prebiotic chemistry, is still not well understood. We have observed that the extent of catalysis depends not only upon the magnitude of the negative charge on the montmorillonite lattice and the number of cations associated with it, but also on the pH at which the reaction is promoted. The isotherm and catalysis studies have been extended to provide binding information and catalytic outcomes over a wide pH range. The optimal binding occurs in the region of maximal oligomer formation. X-ray diffraction studies revealed changes in layer separations of montmorillonite as reaction occurs. The application of the Scherrer equation to the X-ray diffraction data showed differences in domain size. Modeling of the size of the activated nucleotide monomers and the charge on the montmorillonite surface provided an interpretation of how these factors influence adsorption. This research provides a basis for further understanding of the physical processes in the mechanism of this catalysis.