Prebiotic chemistry: a new modus operandi

Abstract

A variety of macromolecules and small molecules-(oligo)nucleotides, proteins, lipids and metabolites-are collectively considered essential to early life. However, previous schemes for the origin of life-e.g. the 'RNA world' hypothesis-have tended to assume the initial emergence of life based on one such molecular class followed by the sequential addition of the others, rather than the emergence of life based on a mixture of all the classes of molecules. This view is in part due to the perceived implausibility of multi-component reaction chemistry producing such a mixture. The concept of systems chemistry challenges such preconceptions by suggesting the possibility of molecular synergism in complex mixtures. If a systems chemistry method to make mixtures of all the classes of molecules considered essential for early life were to be discovered, the significant conceptual difficulties associated with pure RNA, protein, lipid or metabolism 'worlds' would be alleviated. Knowledge of the geochemical conditions conducive to the chemical origins of life is crucial, but cannot be inferred from a planetary sciences approach alone. Instead, insights from the organic reactivity of analytically accessible chemical subsystems can inform the search for the relevant geochemical conditions. If the common set of conditions under which these subsystems work productively, and compatibly, matches plausible geochemistry, an origins of life scenario can be inferred. Using chemical clues from multiple subsystems in this way is akin to triangulation, and constitutes a novel approach to discover the circumstances surrounding the transition from chemistry to biology. Here, we exemplify this strategy by finding common conditions under which chemical subsystems generate nucleotides and lipids in a compatible and potentially synergistic way. The conditions hint at a post-meteoritic impact origin of life scenario.

A Chemical Engineering Perspective on the Origins of Life

“…Powner and co-workers presented an alternative route to pyrimidine nucleoside formation, using reactants that are chemically distinct from nucleobases or sugars [75]. Powner and co-workers also demonstrated a one-pot system that generates both nucleosides and lipids [76]. The source of the phosphorus in nucleotides has been an open question in the field, since most phosphorus would have been stored in minerals such as apatite that are unreactive.…”

The eightfold path to non-enzymatic RNA replication

“…As recently as 2004, Leslie Orgel, one of the great founding fathers of the field of prebiotic chemistry, suggested that "the abiotic synthesis of RNA is so difficult that it is unclear that the RNA World could have evolved de novo on the primitive earth" [3]. While a complete solution to the problem is not yet in hand, major advances have recently been made in this area, primarily from the Sutherland lab [4][5][6], such that there is now considerable optimism that a robust pathway to the assembly of ribonucleotides and RNA oligomers will eventually be found.…”

Prebiotic Systems Chemistry: Complexity Overcoming Clutter

“…1 The small constellation of the core biological metabolites all share an atomic constitution of predominantly hydrogen, carbon, nitrogen, oxygen, phosphorus and sulfur, and these elements serve as the foundations of the triad of organic molecules-nucleic acids, lipids and proteins-that are thought to be immutably linked with sustained biological evolution. [2][3][4][5] There is an irrevocable link between the genetic code, the structure of the 20 proteinogenic amino acids, and the structure of the canonical nucleic acids (RNA and DNA) that is universal across all domains of life. The persistent conservation of these core organic structures is highly indicative of a single origin of life on Earth.…”

“…To some extent, however, understanding why RNA is the ideal candidate as the first information biopolymer of life has been hindered by approaches that have solely concentrated on realizing the prebiotic syntheses of a single class of metabolic macromolecule. 4,5 Replicating nucleic acids are not solitary actors within the biological systems. Cells require a number of chemical subsystems including peptides for functional support, lipids for compartmentalization, and numerous other small molecules that are part of the intricate network that forms the basis of metabolism.…”