Hybrid organic-inorganic structures trigger the formation of primitive cell-like compartments

Abstract

Alkaline hydrothermal vents have become a candidate setting for the origins of life on Earth and beyond. This is due to several key features including the presence of gradients of temperature, redox potential, pH, the availability of inorganic minerals, and the existence of a network of inorganic pore spaces that could have served as primitive compartments. Chemical gardens have long been used as experimental proxies for hydrothermal vents. This paper investigates-10pc]Please note that the spelling of the following author name in the manuscript differs from the spelling provided in the article metadata: Richard J. G. Löffler. The spelling provided in the manuscript has been retained; please confirm. a set of prebiotic interactions between such inorganic structures and fatty alcohols. The integration of a medium-chain fatty alcohol, decanol, within these inorganic minerals, produced a range of emergent 3 dimensions structures at both macroscopic and microscopic scales. Fatty alcohols can be considered plausible prebiotic amphiphiles that might have assisted the formation of protocellular structures such as vesicles. The experiments presented herein show that neither chemical gardens nor decanol alone promote vesicle formation, but chemical gardens grown in the presence of decanol, which is then integrated into inorganic mineral structures, support vesicle formation. These observations suggest that the interaction of fatty alcohols and inorganic mineral structures could have played an important role in the emergence of protocells, yielding support for the evolution of living cells.

Keywords: alkaline hydrothermal vents; inorganic mineral surfaces; origin of life; surface chemistry; vesicles.

Fig. 1.

Vertical and horizontal chemical garden (CG) and variants with decanol added (CGD). In (A) CG: Calcium chloride seeds were dropped upon sodium silicate solution. In (B) CGD, calcium chloride seeds were dropped onto a decanol–silicate two-phase system. In (C) CGD after mixing, calcium chloride seeds dropped upon a decanol–silicate mixed two-phase system. In (D) horizontal variant of the CG system and (E) horizontal variant of the CGD system. Scanning electron microscopy images of samples after 1 d (CG 1 (F) and CGD 1 (G)) and 1 mo (CG 1 (H) and CGD 1 (I)).

Fig. 2.

Long-range XPS spectra for samples CGs and CGDs (low resolution, PE = 50 eV) in A. Short-range spectra for (B) Si2p, (C) Na1s, (D) Ca2p, and (E) 01s. Spectra are not normalized in intensity.

Fig. 3.

CGD crystal-directed vesicle assembly. Vesicle formation was monitored in real time using changes in absorbance values. First, 0.2 M bicine buffer was incubated alone (control) or with CG or CGD samples. Fatty acids/soaps decanoate (DA), myristoleate (MA), or oleate (OA) were then added to the buffered solutions (A). Readings were performed in triplicate, normalized over the weight of crystals introduced in each cuvette and also through pure bicine buffer signal subtraction. Absorbance was registered each second for 10 min, and SE is reported for each 20-s interval. In B, fluorescence imaging of decanoic acid CGD-induced vesicle formation. Size bar 50 microns.