Theoretical studies of structural properties and reaction pathways of prebiotically relevant molecules

Abstract

The present thesis is focused on understanding the origin as well as the composition of primitive genetics. The RNA World hypothesis suggests that RNA was the first biopolymer capable of self-replication and catalysis. In this context, an alternative school of thought suggests the existence of a primitive informational biopolymer called pre RNA as the precedent of modern RNA that contains prebiotic nucleobases that have the ability to spontaneously form glycosidic bonds and select pairing partners. Out of many heterocycles suggested as candidates for prebiotic nucleobase, barbituric acid (BA), melamine (MM), 2,4,6-triaminopyrimidine (TAP) and cyanuric acid (CA) have been found to be most promising. In order to evaluate the candidature of BA, MM, CA and TAP, their physicochemical properties have been evaluated. Further, the structural, energetic and dynamical properties of plausible prebiotic informational polymers formed from incorporation of the CA and TAP have also been investigated using classical molecular dynamics simulation. The inferences from this study blend agreeably with previous experimental results to strengthen the candidature of BA, TAP, CA and MM and derived polymers as components of prebiotic genetics. Additionally, our results from the assessment of noncovalent interactions favour the existence of an intermediate informational polymer containing components of both preRNA and RNA, and the probable evolution of RNA from preRNA via intermediate polymer. The second part of the present thesis explores plausible radical-assisted pathways for the formation of natural nucleobases and prebiotic heterocycles (BA, TAP, CA and MM) from plausible precursors using B3LYP functional coupled with a variety of basis sets. Our computational results from these studies highlight the prebiotic relevance of radical pathways for the formation of natural nucleobases and these heterocycles.