The Effect of the Presence of Amino Acids on the Precipitation of Inorganic Chemical-Garden Membranes: Biomineralization at the Origin of Life

Abstract

If life developed in hydrothermal vents, it would have been within mineral membranes. The first proto-cells must have evolved to manipulate the mineral membranes that formed their compartments in order to control their metabolism. There must have occurred a biological takeover of the self-assembled mineral structures of the vents, with the incorporation of proto-biological molecules within the mineral membranes to alter their properties for life’s purposes. Here, we study a laboratory analogue of this process: chemical-garden precipitation of the amino acids arginine and tryptophan with the metal salt iron chloride and sodium silicate. We produced these chemical gardens using different methodologies in order to determine the dependence of the morphology and chemistry on the growth conditions, as well as the effect of the amino acids on the formation of the iron-silicate chemical garden. We compared the effects of having amino acids initially within the forming chemical garden, corresponding to the internal zones of hydrothermal vents, or else outside, corresponding to the surrounding ocean. The characterization of the formed chemical gardens using X-ray diffraction, Fourier transform infrared spectroscopy, elemental analysis, and scanning electron microscopy demonstrates the presence of amino acids in these structures. The growth method in which the amino acid is initially in the tablet with the iron salt is that which generated chemical gardens with more amino acids in their structures.

Shape Evolution of Precipitate Membranes in Flow Systems

“…Inorganic precipitation reactions can form a wealth of spatial structures ranging from complex three-dimensional microstructures to macroscopic membranes that compartmentalize the reaction system and self-regulate the formation of additional precipitate. − Many of these structures share no similarities with euhedral crystals but are smoothly curved and reminiscent of shapes more closely associated with living systems. − This morphological similarity between abiotic and biological systems continues to cause problems for the identification of Earth’s earliest microfossils as well as the search for remnants of life on other planets. − Inorganic precipitate membranes are also of interest to origins of life research. − In this context, hydrothermal vents have attracted considerable attention. − They arise near fissures on the ocean floor, eject mineral-rich hot water into the cold ocean, and erect tall chimney structures. These precipitate towers are usually classified as white or black smokers depending on their hue and mineral composition. , Black smokers are rich in iron and nickel precipitates, whichas slurries in laboratory settingscatalyze the carbon-monoxide-driven formation of α-hydroxy and α-amino acids. , …”

Nitrate Reactivity in Iron (Oxy)hydroxide Systems: Effect of pH, Iron Redox State, and Phosphate

“…We originally hypothesized that the discrepancy could be due to different minerals forming at different pH values; however, VNIR showed that both reactions showed low reflectance consistent with magnetite (Figure A); this was further corroborated with XRD (Figure ) that suggested magnetite was formed in both reactions (RRUFF ID: R061111.9). The additional XRD peaks located at 32 and 46° likely correspond to highly crystalline halite (NaCl); and in these samples, no other crystalline material was observed to be present.…”

Prebiotic Chemistry Experiments Using Microfluidic Devices

“…Different methods can be employed to put the two solutions in contact, e.g., by adding drops of one solution to the other [ 54 , 68 ] or by injecting the hydrothermal fluid into a reservoir containing the oceanic solution [ 64 , 65 , 66 , 67 ]. The contact of the two solutions creates hollow structures called chemical gardens [ 69 , 70 ]. Chemical gardens are thus inorganic structures formed by the reaction of a soluble metallic salt and an aqueous solution of anions [ 71 ].…”