2014 Annual Science Report
Rensselaer Polytechnic Institute Reporting | SEP 2013 – DEC 2014
Project 7: Microenvironmental Influences on Prebiotic Synthesis
Before biotic, i.e., “biologically-derived” pathways for the formation of essential biological molecules such as RNA, DNA and proteins could commence, abiotic pathways were needed to form the molecules that were the basis for the earliest life. Much research has been done on possible non-biological routes to synthesis of RNA, thought by many to be the best candidate or model for the emergence of life. Our work focuses on possible physicochemical microenvironments and processes on early earth that could have influenced and even directed or templated the formation of RNA or its predecessors.
Our research has focused on RNA polymerization in prebiotic Earth, emphasizing the interface between prebiotic chemistry and early Earth environments. We have continued our studies of RNA polymerization reactions of activated and unactivated nucleotides in the absence and presence of montmorrilonite clay catalysis, with a view toward understanding the previously unexplored effects of nucleotide aggregation and self-assembly on the polymerization reactions. This includes studies of the unique self-assembly of guanosine nucleotides to form G-quadruplex structures in the presence of other nucleotides, which could affect the availability of the nucleotides for polymerization reactions and also provide potential templates for polymerization (Cassidy et al. 2014). These studies also include inosine monophosphate in addition to the canonical ribonucleotides. Inosine is of particular interest because, like guanosine, it is capable of self-assembly into quadruplex structures. In collaboration with Dr. Laurie Barge of the JPL, we initiated studies of RNA polymerization in simulated hydrothermal vent systems, which has never before been examined. Our results show that, under certain conditions, both activated and unactivated AMP undergo modest polymerization (Burcar, B.T., Barge, L.M., Trail, D., Watson, E.B., Russell, M.J., McGown, L.B., “RNA Oligomerization in Laboratory Analogues of Alkaline Hydrothermal Vent Systems”, submitted to Astrobiology). These preliminary results are important for future consideration of deep ocean hydrothermal environments in RNA World research. We demonstrated the effectiveness of a new approach to nucleotide activation that is performed on-the-fly during the polymerization experiment, instead of the traditional approach of nucleotide pre-activation (Burcar et al., in press). The key advantage of this approach is that it is performed in the aqueous solution in which polymerization occurs, in real time. Building on the chimney studies, we collaborated with NYCA colleagues Karyn Rogers and Bruce Watson to explore the effects of high pressures in combination with temperature on RNA polymerization, nucleotide aggregation, and polymer stability. Initial results indicate that pressure does affect the yield of polymerization and the relative proportion of single, linear strands to aggregates. There is an increase in length of the polymerization products over time, after which the products appear to degrade, and this time varies with pressure.
In a separate study funded in part by NYCA, we explored the structural basis for chiral selectivity exhibited by self-assembled guanosine monophosphate toward enantiomers of amino acids and other compounds (Gupta et al. 2014). This is a potentially important source of chiral selectivity in early life.
Cassidy, L. M., Burcar, B. T., Stevens, W., Moriarty, E. M., & McGown, L. B. (2014). Guanine-Centric Self-Assembly of Nucleotides in Water: An Important Consideration in Prebiotic Chemistry. Astrobiology, 14(10), 876–886. doi:10.1089/ast.2014.1155
Gupta, A. P., Taylor, W. J., McGown, L. B., & Kempf, J. G. (2014). NMR Studies of the Chiral Selectivity of Self-Assembled Guanosinemonophosphate. J. Phys. Chem. B, 118(49), 14243–14256. doi:10.1021/jp5075016
PROJECT MEMBERS:Linda McGown
RELATED OBJECTIVES:Objective 3.1
Sources of prebiotic materials and catalysts
Origins and evolution of functional biomolecules
Origins of energy transduction
Origins of cellularity and protobiological systems