Aqueous abiotic methane concentrations in a range of geologic settings are below levels expected for equilibrium with coexisting CO2 and H-2, indicating that kinetics can control the speciation of reduced carbon-bearing fluids. Previous studies have suggested that mineral catalysts or gas-phase reactions may increase the rate of methanogenesis. Here, we report on experiments that indicate pressure can also accelerate aqueous reduction of CO2 to CH4. Four series of cold-seal hydrothermal experiments were performed from 1 to 3.5 kbar at 300 degrees C for two weeks and analyzed using gas chromatography/mass spectrometry. The starting fluids were 10-20-mu L solutions of 70-mmolal C-13-labeled formic acid ((HCOOH)-C-13) contained in welded gold capsules. Increasing pressure (P) resulted in a systematic, reproducible log-linear increase in (CH4)-C-13 yields. The pressure effect could be quantified the log-linear slope, Delta log[(CH4)-C-13]/Delta P (log mmolal per kbar). The mean slope was 0.66 +/- 0.05 (+/- 1s.e.), indicating that (CH4)-C-13 yields increased by an average factor of 40-50 over a P range of 2.5 kbar. Pressure-independent variations in [(CH4)-C-13] were observed as scatter about the log-linear regressions and as variations in the y-intercepts of the regressions. These variations were attributed to trace amounts of catalytic Fe along the inner capsule wall that remained despite cleaning the Au capsules in nitric acid prior to each experimental series. The mechanism for the pressure-dependent effect was interpreted to result from one or more of the following three processes: reduction of a metastable reaction intermediate such as methanol, formation of Fe-carbonyl complexes in the fluid, and/or heterogeneous catalysis by Fe. The results suggest that pressure may influence aqueous abiotic CH4 yields in certain geological environments, particularly when the relative effects of other kinetic factors such as temperature are diminished, e. g., in cool forearcs or other settings with a steep geothermal gradient. Because the experiments were performed over a limited pressure range, even modest isothermal increases in pressure may substantially enhance CH4 yields. A kinetic pressure effect may be especially important on the deep ocean floors of planetary bodies where pressure may compensate for the otherwise sluggish reaction kinetics expected at low T. (C) 2014 Elsevier Ltd. All rights reserved.

Proteins are responsible multiple biological functions, such as ligand binding, catalysis, and ion channeling. This functionality is enabled by proteins' three-dimensional structures that require long polypeptides. Since plausibly prebiotic synthesis of functional polypeptides has proven challenging in the laboratory, we propose that these functions may have been initially performed by alternative macromolecular constructs, namely hyperbranched polymers (HBPs), during early stages of chemical evolution. HBPs can be straightforwardly synthesized in one-pot processes, possess globular structures determined by their architecture as opposed to folding in proteins, and have documented ligand binding and catalytic properties. Our initial study focuses on glycerol-citric acid HBPs synthesized via moderate heating in the dry state. The polymerization products consisted of a mixture of isomeric structures of varying molar mass as evidenced by NMR, mass spectrometry and size-exclusion chromatography. Addition of divalent cations during polymerization resulted in increased incorporation of citric acid into the HBPs and the possible formation of cation-oligomer complexes. The chelating properties of citric acid govern the makeup of the resulting polymer, turning the polymerization system into a rudimentary smart material.

Low-dimensional carbon nanomaterials such as fullerenes, nanotubes, graphene and diamondoids have extraordinary physical and chemical properties(1,2). Compression-induced polymerization of aromatic molecules could provide a viable synthetic route to ordered carbon nanomaterials(3,4), but despite almost a century of study(5-9) this approach has produced only amorphous products(10-14). Here we report recovery to ambient pressure of macroscopic quantities of a crystalline one-dimensional sp(3) carbon nanomaterial formed by high-pressure solid-state reaction of benzene. X-ray and neutron diffraction, Raman spectroscopy, solid-state NMR, transmission electron microscopy and first-principles calculations reveal close-packed bundles of subnanometre-diameter sp(3)-bonded carbon threads capped with hydrogen, crystalline in two dimensions and short-range ordered in the third. These nanothreads promise extraordinary properties such as strength and stiffness higher than that of sp(2) carbon nanotubes or conventional high-strength polymers(15). They may be the first member of a new class of ordered sp(3) nanomaterials synthesized by kinetic control of high-pressure solid-state reactions.

Acetonitrile (CH3CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C N triple bond, while the C-H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonstrated that C-H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH center dot center dot center dot N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp(2) and sp(3) bonded carbon. Finally, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C-H can be activated by high pressure, even at room temperature and without a catalyst.

Primitive xenolithic clasts, often referred to as `` dark clasts", are well known in many regolith breccias. The Sharps H3.4 ordinary chondrite contains unusually large dark clasts up to similar to 1 cm across. Poorly-graphitized carbon (PGC), with Fe, Ni metal and described as `` carbon-rich aggregates", has been reported in these clasts (Brearley, 1990). We report detailed analyses of carbonaceous matter in several identical Sharps clasts using FTIR, Raman, C-XANES, and TEM that provide insight on the extent of thermal processing and possible origin of such clasts. We also prepared acid residues of the clasts using the HCl/HF method and conducted mass spectrometric analysis of the entrained noble gases.

Geometric isomerism in polyacetylene is a basic concept in chemistry textbooks. Polymerization to cis-isomer is kinetically preferred at low temperature, not only in the classic catalytic reaction in solution but also, unexpectedly, in the crystalline phase when it is driven by external pressure without a catalyst. Until now, no perfect reaction route has been proposed for this pressure-induced polymerization. Using in situ neutron diffraction and meta-dynamic simulation, we discovered that under high pressure, acetylene molecules react along a specific crystallographic direction that is perpendicular to those previously proposed. Following this route produces a pure cis-isomer and more surprisingly, predicts that graphane is the final product. Experimentally, polycyclic polymers with a layered structure were identified in the recovered product by solid-state nuclear magnetic resonance and neutron pair distribution functions, which indicates the possibility of synthesizing graphane under high pressure.

Hydrothermal systems may have been favorable environments for the evolution of prebiotic chemistry on early Earth due to the presence of chemical, temperature, and redox gradients that could promote the formation of biomolecules. However, the relevance of these environments in origins of life scenarios has been debated due to rapid decomposition of biologically essential species, such as amino acids, at high temperatures. Little is known about the reactivity of amino acids in the presence of mineral surfaces and reducing conditions, which reflect the geochemical complexities of environments such as serpentinite-hosted hydrothermal vents. We investigated the decomposition of 25 mM aspartate at 200 degrees C and 15.5 bars (P-SAT) in gold capsules both with and without brucite [Mg(OH)(2)], a mineral product of serpentinization, and reducing conditions (NH4Cl and H-2(aq)).We observed that the reaction products of aspartate vary significantly with the initial reaction conditions. Fluids containing aspartate only decomposed to fumarate, maleate, malate, acetate, and trace amounts of succinate and glycine. However, under reducing conditions, the main product was succinate (8 mM) and also approximately 1 mM total of the amino acids glycine, alpha-alanine, and beta-alanine. The amount of a-alanine increased three-fold with brucite. Furthermore, we detected a two-fold decrease in the fumarate concentration, whereas total maleate concentration dramatically decreased over ten-fold and resulted in an overall increase in the trans/cis ratio of these deamination products of aspartate from 0.9 to 4.5 as a function of brucite loading. This net decrease in fumarate and maleate concentration and the five-fold increase in the trans/cis ratio might have been caused by a combination of a pH increase and the formation of magnesite due to increased Mg2+ ion concentration. The results of this study provide evidence that the fundamental properties of a hydrothermal system, including mineral assemblages, reducing conditions, and dissolved species concentrations, will influence the fate of amino acids at high temperature.

Enzymes are biopolymeric complexes that catalyse biochemical reactions and shape metabolic pathways. Enzymes usually work with small molecule cofactors that actively participate in reaction mechanisms and complex, usually globular, polymeric structures capable of specific substrate binding, encapsulation and orientation. Moreover, the globular structures of enzymes possess cavities with modulated microenvironments, facilitating the progression of reaction(s). The globular structure is ensured by long folded protein or RNA strands. Synthesis of such elaborate complexes has proven difficult under prebiotically plausible conditions. We explore here that catalysis may have been performed by alternative polymeric structures, namely hyperbranched polymers. Hyper-branched polymers are relatively complex structures that can be synthesized under prebiotically plausible conditions; their globular structure is ensured by virtue of their architecture rather than folding. In this study, we probe the ability of tertiary amine-bearing hyperbranched polyesters to form hydrophobic pockets as a reaction-promoting medium for the Kemp elimination reaction. Our results show that polyesters formed upon reaction between glycerol, triethanolamine and organic acid containing hydrophobic groups, i.e. adipic and methylsuccinic acid, are capable of increasing the rate of Kemp elimination by a factor of up to 3 over monomeric triethanolamine.

Over the last several hundred years of scientific progress, we have arrived at a deep understanding of the non-living world. We have not yet achieved an analogous, deep understanding of the living world. The origins of life is our best chance at discovering scientific laws governing life, because it marks the point of departure from the predictable physical and chemical world to the novel, history-dependent living world. This theme issue aims to explore ways to build a deeper understanding of the nature of biology, by modelling the origins of life on a sufficiently abstract level, starting from prebiotic conditions on Earth and possibly on other planets and bridging quantitative frameworks approaching universal aspects of life. The aim of the editors is to stimulate new directions for solving the origins of life. The present introduction represents the point of view of the editors on some of the most promising future directions.

Pressure-induced polymerization (PIP) of aromatics is a novel method for constructing sp(3)-carbon frameworks, and nanothreads with diamond-like structures were synthesized by compressing benzene and its derivatives. Here by compressing a benzene-hexafluorobenzene cocrystal (CHCF), H-F-substituted graphane with a layered structure in the PIP product was identified. Based on the crystal structure determined from the in situ neutron diffraction and the intermediate products identified by gas chromatography-mass spectrum, we found that at 20 GPa CHCF forms tilted columns with benzene and hexafluorobenzene stacked alternatively, and leads to a [4+2] polymer, which then transforms to short-range ordered H-F-substituted graphane. The reaction process involves [4+2] Diels-Alder, retro-Diels-Alder, and 1-1' coupling reactions, and the former is the key reaction in the PIP. These studies confirm the elemental reactions of PIP of CHCF for the first time, and provide insight into the PIP of aromatics.