2014 Annual Science Report
Rensselaer Polytechnic Institute Reporting | SEP 2013 – DEC 2014
Project 6: Prebiotic Chemical Catalysis on Early Earth and Mars
The “RNA World” hypothesis is the current paradigm for the origins of terrestrial life. Our research is aimed at testing a key component of this paradigm: the efficiency with which RNA molecules form and grow under realistic conditions. We are studying abiotic production and polymerization of RNA by catalysis on montmorillonite clays. The catalytic efficiency of different montmorillonites are determined and compared, with the goal of determining which properties distinguish good catalysts from poor catalysts. We are also investigating the origin of montmorillonites, to test their probable availability on the early Earth and Mars, and the nature of catalytic activity that could have led to chiral selectivity on Earth.
We have shown progress in demonstrating chiral selectivity in the montmorillonite-catalyzed synthesis of RNA-type oligomers from 5’-phosphorimidazolides of D, L-adenosine and D, L-uridine. This reaction was in contrast with the non-enzymatic template directed synthesis where elongation terminates after addition of an L-monomer in the RNA chain. Biomolecular chirality is a signature of life; therefore, we are continuing this investigation in an even more complex reaction mixture of 5’-phosphorimidazolides of D, L-adenosine, D, L-uridine, D, L-guanosine and D, L-cytidine. In another study we have shown significant role of mineral salts (e.g., NaCl) in RNA synthesis catalyzed by montmorillonite. Maximum catalytic activity was observed with NaCl at a concentration between 0.8 and 1.2M. This concentration of NaCl resembled its abundance in the ancient oceans (0.9-1.2M). The role of fluoride ions was also investigated and a 5’-phosphorofluoridate adduct with adenosine was identified and characterized. The surface layer charge of catalytic vs. non-catalytic clay minerals was determined for understanding the physical processes in the mechanism of clay mineral catalysis. The results suggested that more clay minerals than hitherto expected may have the ability to catalyze RNA synthesis at short oligonucleotide level. Terahertz frequency optical constants of montmorillonite were characterized for an in-situ evaluation of the catalytic properties of montmorillonite at the molecular level. We are currently investigating whether terrestrial, catalytically active montmorillonites generated on Earth by the Banin procedure can also become catalytically active following a process involving H2SO4, which is a source of acidity for Martian conditions. The presence of montmorillonite on Mars suggests that these processes may have taken place there as well.
PROJECT MEMBERS:Prakash Joshi
RELATED OBJECTIVES:Objective 3.1
Sources of prebiotic materials and catalysts
Origins and evolution of functional biomolecules