Water–Air Interfaces as Environments to Address the Water Paradox in Prebiotic Chemistry: A Physical Chemistry Perspective

Abstract

The asymmetric water–air interface provides a dynamic aqueous environment with properties that are often very different than bulk aqueous or gaseous phases and promotes reactions that are thermodynamically, kinetically, or otherwise unfavorable in bulk water. Prebiotic chemistry faces a key challenge: water is necessary for life yet reduces the efficiency of many biomolecular synthesis reactions. This perspective considers water–air interfaces as auspicious reaction environments for abiotic synthesis. We discuss recent evidence that (1) water–air interfaces promote condensation reactions including peptide synthesis, phosphorylation, and oligomerization; (2) photochemistry at water–air interfaces may have been a significant source of prebiotic molecular complexity, given the lack of oxygen and increased availability of near-ultraviolet radiation on early Earth; and (3) water–air interfaces can promote spontaneous reduction and oxidation reactions, potentially providing protometabolic pathways. Life likely began within a relatively short time frame, and water–air interfaces offer promising environments for simultaneous and efficient biomolecule production.

Protometabolism as out-of-equilibrium chemistry

“…Energy is not a unique property of hydrothermal vents. The Sun is a clear example of a prebiotic energy source that would have been inaccessible in the deep sea [3,17,44], and chemical energy sources, e.g. isonitriles, likely drove prebiotic chemistry forward [82].…”

“…Regardless of the vantage point, what works on prebiotic analogues of anabolism have in common is an attempt to understand how larger biological molecules could have been synthesized prebiotically from smaller, abundant chemical resources. Although there were early, important studies on the prebiotic synthesis of biological molecules [15,16], modern work applies knowledge of synthetic organic chemistry to reactions in water or at the air–water interface [17], under prebiotically plausible conditions. As CO 2 was more abundant on the prebiotic Earth, and as the Wood–Ljungdahl pathway (or the reductive acetyl-coenzyme A pathway) has been hypothesized to have been exploited by LUCA, CO 2 often features as a carbon source for the synthesis of more complex molecules.…”

Emerging investigator series: surfactants, films, and coatings on atmospheric aerosol particles: a review

“…4–7 Other species form through secondary reactions in the atmosphere—either through heterogeneous reactions, through gas-phase reactions that produce low-volatile, poorly soluble products that adsorb to aerosol particles, or through particle-phase reactions that form surface-active species. 3,8–19…”

“…[4][5][6][7] Other species form through secondary reactions in the atmosphere-either through heterogeneous reactions, through gas-phase reactions that produce low-volatile, poorly soluble products that adsorb to aerosol particles, or through particlephase reactions that form surface-active species. 3,[8][9][10][11][12][13][14][15][16][17][18][19] As a class, surfactants encompass anionic, cationic, and nonionic species. Adsorption isotherms use principles of thermodynamics to model their partitioning to the air-water interface.…”

Interface Asymmetry Induced and Surface Pressure Controlled Valence Tautomerism in Monolayers of bis-Phthalocyaninates of Lanthanides

“…Nevertheless, while the effect of pressure on the processes of redox isomerization is mentioned in the literature for bulk samples [16][17][18], for surface/interfacial systems this issue remains poorly investigated. Meanwhile, the intrinsically asymmetric nature of air/water and air/solid interfaces often enables processes which can be almost impossible in bulk media [19,20].…”