Molecular Evolution in a Peptide-Vesicle System

Based on a new model of a possible origin of life, we propose an efficient and stable system undergoing structural reproduction, self-optimization, and molecular evolution. This system is being formed under realistic conditions by the interaction of two cyclic processes, one of which offers vesicles as the structural environment, with the other supplying peptides from a variety of amino acids as versatile building blocks. We demonstrate that structures growing in a combination of both cycles have the potential to support their own existence, to undergo chemical and structural evolution, and to develop unpredicted functional properties. The key mechanism is the mutual stabilization of the peptides by the vesicles and of the vesicles by the peptides together with a constant production and selection of both. The development of the proposed system over time would not only represent one of the principles of life, but could also be a model for the formation of self-evolving structures ultimately leading to the first living cell. The experiment yields clear evidence for a vesicle-induced accumulation of membrane-interacting peptide which could be identified by liquid chromatography combined with high-resolution mass spectroscopy. We found that the selected peptide has an immediate effect on the vesicles, leading to (i) reduced vesicle size, (ii) increased vesicle membrane permeability, and (iii) improved thermal vesicle stability

Chemical Analysis of a “Miller-Type” Complex Prebiotic Broth: Part II: Gas, Oil, Water and the Oil/Water-Interface

We have analyzed the chemical variety obtained by Miller-Urey-type experiments using nuclear magnetic resonance (NMR) spectroscopy and coherent anti-Stokes Raman scattering (CARS) spectroscopy, gas chromatography followed by mass spectrometry (GC/MS) and two-dimensional gas chromatography followed by mass spectrometry (GCxGC/MS). In the course of a running Miller-Urey-type experiment, a hydrophobic organic layer emerged besides the hydrophilic aqueous phase and the gaseous phase that were initially present. The gas phase mainly consisted of aromatic compounds and molecules containing C≡C or C≡N triple bonds. The hydrophilic phase contained at least a few thousands of different molecules, primarily distributed in a range of 50 and 500 Da. The hydrophobic phase is characterized by carbon-rich, oil-like compounds and their amphiphilic derivatives containing oxygen with tensioactive properties. The presence of a wide range of oxidized molecules hints to the availability of oxygen radicals. We suggest that they intervene in the formation of alkylated polyethylene glycol (PEG) in the oil/water interface. CARS spectroscopy revealed distinct vibrational molecular signatures. In particular, characteristic spectral bands for cyanide compounds were observed if the broth was prepared with electric discharges in the gaseous phase. The characteristic spectral bands were absent if discharges were released onto the water surface. NMR spectroscopy on the same set of samples independently confirmed the observation. In addition, NMR spectroscopy revealed overall high chemical variability that suggests strong non-linearities due to interdependent, sequential reaction steps. © 2016 The Author(s)Saarland UniversityHSFPEU/FP7/HEALTH-F5-2008-20082

Organic compounds in fluid inclusions of Archean quartz—Analogues of prebiotic chemistry on early Earth

<div><p>The origin of life is still an unsolved mystery in science. Hypothetically, prebiotic chemistry and the formation of protocells may have evolved in the hydrothermal environment of tectonic fault zones in the upper continental crust, an environment where sensitive molecules are protected against degradation induced e.g. by UV radiation. The composition of fluid inclusions in minerals such as quartz crystals which have grown in this environment during the Archean period might provide important information about the first organic molecules formed by hydrothermal synthesis. Here we present evidence for organic compounds which were preserved in fluid inclusions of Archean quartz minerals from Western Australia. We found a variety of organic compounds such as alkanes, halocarbons, alcohols and aldehydes which unambiguously show that simple and even more complex prebiotic organic molecules have been formed by hydrothermal processes. Stable-isotope analysis confirms that the methane found in the inclusions has most likely been formed from abiotic sources by hydrothermal chemistry. Obviously, the liquid phase in the continental Archean crust provided an interesting choice of functional organic molecules. We conclude that organic substances such as these could have made an important contribution to prebiotic chemistry which might eventually have led to the formation of living cells.</p></div

Organic compounds identified in hydrothermally grown quartz crystals near Jack Hills in Western Australia.

<p>The index letter “a” refers to the technical approach used for the analysis: a = 1 for one-dimensional gas chromatography with flame ionization detector⁸, a = 2 for comprehensive two-dimensional gas chromatography coupled to a quadrupole MS and a = 3 for liquid chromatography with a high-resolution TOF-MS.</p

Stable carbon (δ¹³C) and hydrogen isotope (δ²H) composition of CH₄ in the fluid inclusions of Australian quartz samples.

<p>For comparison, the plot shows data regions typical for biogenic sources (green), thermogenic sources (red) and abiotic sources (black) (modified after Etiope and Sherwood Lollar [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177570#pone.0177570.ref023" target="_blank">23</a>]). The codes assigned to the data points (black open squares) refer to the sample locations and are explained in Text A in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177570#pone.0177570.s001" target="_blank">S1 File</a>.</p

Remnant of a typical hydrothermal quartz dyke in the northern Jack Hills region / Western Australia which crystallized presumably in Archaean time in deeper parts of a shear-dominated crust (photograph by Thomas Kirnbauer, with permission).

<p>Remnant of a typical hydrothermal quartz dyke in the northern Jack Hills region / Western Australia which crystallized presumably in Archaean time in deeper parts of a shear-dominated crust (photograph by Thomas Kirnbauer, with permission).</p