Experimentally Tracing the Key Steps in the Origin of Life: The Aromatic World

Abstract

Life is generally believed to emerge on Earth, to be at least functionally similar to life as we know it today, and to be much simpler than modern life. Although minimal life is notoriously difficult to define, a molecular system can be considered alive if it turns resources into building blocks, replicates, and evolves. Primitive life may have consisted of a compartmentalized genetic system coupled with an energy-harvesting mechanism. How prebiotic building blocks self-assemble and transform themselves into a minimal living system can be broken into two questions: (1) How can prebiotic building blocks form containers, metabolic networks, and informational polymers? (2) How can these three components cooperatively organize to form a protocell that satisfies the minimal requirements for a living system? The functional integration of these components is a difficult puzzle that requires cooperation among all the aspects of protocell assembly: starting material, reaction mechanisms, thermodynamics, and the integration of the inheritance, metabolism, and container functionalities. Protocells may have been self-assembled from components different from those used in modern biochemistry. We propose that assemblies based on aromatic hydrocarbons may have been the most abundant flexible and stable organic materials on the primitive Earth and discuss their possible integration into a minimal life form. In this paper we attempt to combine current knowledge of the composition of prebiotic organic material of extraterrestrial and terrestrial origin, and put these in the context of possible prebiotic scenarios. We also describe laboratory experiments that might help clarify the transition from nonliving to living matter using aromatic material. This paper presents an interdisciplinary approach to interface state of the art knowledge in astrochemistry, prebiotic chemistry, and artificial life research.

Photochemically driven redox chemistry induces protocell membrane pearling and division

“…PAHs are the most abundant polyatomic organic molecules in the universe, have been postulated to play important roles in the origin of life (16,17), and have been shown to stabilize short-chain fatty acid membranes (18). We therefore asked whether oxygenated derivatives of PAHs, such as 1-hydroxypyrene (while HPTS itself is also a hydroxypyrene derivative, it is unlikely to be prebiotically abundant), can be incorporated into vesicle membranes and act as photosensitizers that can absorb UV radiation, generate ROS, and facilitate the division of protocells.…”

The Role of Biomacromolecular Crowding, Ionic Strength, and Physicochemical Gradients in the Complexities of Life's Emergence

“…Possibly, the first communities of such physicochemical units were the gel-like membranous FeS bubbles produced at alkaline hydrothermal vents (66,98). Later, with the appearance of land, organic microspaces could have appeared, e.g., they could have emerged and evolved by drying and rewetting cycles from dissolved and suspended "cosmological oligomers" derived from hydrogen cyanide and from polyaromatic hydrocarbons (12,25,68), as further described in "Organic polymers and oligomers available on Hadean Earth" in the Appendix.…”

Formation and stability of hydrogenated PAHs in the gas phase

“…Despite this, their role in interstellar chemistry remains largely unexplored. It has been suggested that PAHs may be intimately involved in the molecular origin of life (Ehrenfreund et al 2006;Herd et al 2011) and that they may act as interstellar catalysts for the formation of molecular hydrogen (H 2 ; Habart et al 2004;Rauls & Hornekaer 2008), the most abundant molecule in space.…”