Redox and pH gradients drive amino acid synthesis in iron oxyhydroxide mineral systems

Iron oxyhydroxide minerals, known to be chemically reactive and significant for elemental cycling, are thought to have been abundant in early-Earth seawater, sediments, and hydrothermal systems. In the anoxic Fe^(2+)-rich early oceans, these minerals would have been only partially oxidized and thus redox-active, perhaps able to promote prebiotic chemical reactions. We show that pyruvate, a simple organic molecule that can form in hydrothermal systems, can undergo reductive amination in the presence of mixed-valence iron oxyhydroxides to form the amino acid alanine, as well as the reduced product lactate. Furthermore, geochemical gradients of pH, redox, and temperature in iron oxyhydroxide systems affect product selectivity. The maximum yield of alanine was observed when the iron oxyhydroxide mineral contained 1:1 Fe(II):Fe(III), under alkaline conditions, and at moderately warm temperatures. These represent conditions that may be found, for example, in iron-containing sediments near an alkaline hydrothermal vent system. The partially oxidized state of the precipitate was significant in promoting amino acid formation: Purely ferrous hydroxides did not drive reductive amination but instead promoted pyruvate reduction to lactate, and ferric hydroxides did not result in any reaction. Prebiotic chemistry driven by redox-active iron hydroxide minerals on the early Earth would therefore be strongly affected by geochemical gradients of E_h, pH, and temperature, and liquid-phase products would be able to diffuse to other conditions within the sediment column to participate in further reactions

Greenalite Nanoparticles in Alkaline Vent Plumes as Templates for the Origin of Life

Mineral templates are thought to have played keys roles in the emergence of life. Drawing on recent findings from 3.45–2.45 billion-year-old iron-rich hydrothermal sedimentary rocks, we hypothesize that greenalite (Fe₃Si₂O₅ (OH)₄) was a readily available mineral in hydrothermal environments, where it may have acted as a template and catalyst in polymerization, vesicle formation and encapsulation, and protocell replication. We argue that venting of dissolved Fe²⁺ and SiO₂ (aq) into the anoxic Hadean ocean favored the precipitation of nanometer-sized particles of greenalite in hydrothermal plumes, producing a continuous flow of free-floating clay templates that traversed the ocean. The mixing of acidic, metal-bearing hydrothermal plumes from volcanic ridge systems with more alkaline, organic-bearing plumes generated by serpentinization of ultramafic rocks brought together essential building blocks for life in solutions conducive to greenalite precipitation. We suggest that the extreme disorder in the greenalite crystal lattice, producing structural modulations resembling parallel corrugations (∼22 Å wide) on particle edges, promoted the assembly and alignment of linear RNA-type molecules (∼20 Å diameter). In alkaline solutions, greenalite nanoparticles could have accelerated the growth of membrane vesicles, while their encapsulation allowed RNA-type molecules to continue to form on the mineral templates, potentially enhancing the growth and division of primitive cell membranes. Once self-replicating RNA evolved, the mineral template became redundant, and protocells were free to replicate and roam the ocean realm

Abiotic ammonium formation in the presence of Ni-Fe metals and alloys and its implications for the Hadean nitrogen cycle

Experiments with dinitrogen-, nitrite-, nitrate-containing solutions were conducted without headspace in Ti reactors (200°C), borosilicate septum bottles (70°C) and HDPE tubes (22°C) in the presence of Fe and Ni metal, awaruite (Ni80Fe20) and tetrataenite (Ni50Fe50). In general, metals used in this investigation were more reactive than alloys toward all investigated nitrogen species. Nitrite and nitrate were converted to ammonium more rapidly than dinitrogen, and the reduction process had a strong temperature dependence. We concluded from our experimental observations that Hadean submarine hydrothermal systems could have supplied significant quantities of ammonium for reactions that are generally associated with prebiotic synthesis, especially in localized environments. Several natural meteorites (octahedrites) were found to contain up to 22 ppm Ntot. While the oxidation state of N in the octahedrites was not determined, XPS analysis of metals and alloys used in the study shows that N is likely present as nitride (N3-). This observation may have implications toward the Hadean environment, since, terrestrial (e.g., oceanic) ammonium production may have been supplemented by reduced nitrogen delivered by metal-rich meteorites. This notion is based on the fact that nitrogen dissolves into metallic melts

Greenalite Nanoparticles in Alkaline Vent Plumes as Templates for the Origin of Life

Mineral templates are thought to have played keys roles in the emergence of life. Drawing on recent findings from 3.45–2.45 billion-year-old iron-rich hydrothermal sedimentary rocks, we hypothesize that greenalite (Fe₃Si₂O₅ (OH)₄) was a readily available mineral in hydrothermal environments, where it may have acted as a template and catalyst in polymerization, vesicle formation and encapsulation, and protocell replication. We argue that venting of dissolved Fe²⁺ and SiO₂ (aq) into the anoxic Hadean ocean favored the precipitation of nanometer-sized particles of greenalite in hydrothermal plumes, producing a continuous flow of free-floating clay templates that traversed the ocean. The mixing of acidic, metal-bearing hydrothermal plumes from volcanic ridge systems with more alkaline, organic-bearing plumes generated by serpentinization of ultramafic rocks brought together essential building blocks for life in solutions conducive to greenalite precipitation. We suggest that the extreme disorder in the greenalite crystal lattice, producing structural modulations resembling parallel corrugations (∼22 Å wide) on particle edges, promoted the assembly and alignment of linear RNA-type molecules (∼20 Å diameter). In alkaline solutions, greenalite nanoparticles could have accelerated the growth of membrane vesicles, while their encapsulation allowed RNA-type molecules to continue to form on the mineral templates, potentially enhancing the growth and division of primitive cell membranes. Once self-replicating RNA evolved, the mineral template became redundant, and protocells were free to replicate and roam the ocean realm

Study on the Performance of New Imidazoline Electromigration Inhibitor in Reinforced Concrete

Steel bars inside reinforced concrete easily become corroded in high chloride environments, bidirectional electromigration rehabilitation is an important method of repairing the durability of reinforced concrete, it can migrate chloride out of concrete and transfer electromigration inhibitor to the surface of the steel bar under the action of an electric field. In this paper, autonomous synthesis electromigration inhibitor was used with bidirectional electromigration rehabilitation to repair the durability of reinforced concrete. Specifically, the effect of a new imidazoline corrosion inhibitor on chloride migration, corrosion potential, and reinforcement of concrete strength was explored. The research results showed that the dechlorination effect and electrochemical dechlorination made no significant difference on the surface of the concrete, where chlorine removal efficiency was more than 70% and the location of steel efficiency of chlorine was more than 90%. The autonomous synthesis electromigration inhibitor was found to be excellent at facilitating chloride migration and ameliorating corrosion, meanwhile, it had a negligible impact on the concrete strength

Oxidation of Cr(III)-Fe(III) Mixed-Phase Hydroxides by Chlorine: Implications on the Control of Hexavalent Chromium in Drinking Water.

The occurrence of chromium (Cr) as an inorganic contaminant in drinking water is widely reported. One source of Cr is its accumulation in iron-containing corrosion scales of drinking water distribution systems as Cr(III)-Fe(III) hydroxide, that is, Fe xCr(1- x)(OH)3(s), where x represents the Fe(III) molar content and typically varies between 0.25 and 0.75. This study investigated the kinetics of inadvertent hexavalent chromium Cr(VI) formation via the oxidation of Fe xCr(1- x)(OH)3(s) by chlorine as a residual disinfectant in drinking water, and examined the impacts of Fe(III) content and drinking water chemical parameters including pH, bromide and bicarbonate on the rate of Cr(VI) formation. Data showed that an increase in Fe(III) molar content resulted in a significant decrease in the stoichiometric Cr(VI) yield and the rate of Cr(VI) formation, mainly due to chlorine decay induced by Fe(III) surface sites. An increase in bicarbonate enhanced the rate of Cr(VI) formation, likely due to the formation of Fe(III)-carbonato surface complexes that slowed down the scavenging reaction with chlorine. The presence of bromide significantly accelerated the oxidation of Fe xCr(1- x)(OH)3(s) by chlorine, resulting from the catalytic effect of bromide acting as an electron shuttle. A higher solution pH between 6 and 8.5 slowed down the oxidation of Cr(III) by chlorine. These findings suggested that the oxidative conversion of chromium-containing iron corrosion products in drinking water distribution systems can lead to the occurrence of Cr(VI) at the tap, and the abundance of iron, and a careful control of pH, bicarbonate and bromide levels can assist the control of Cr(VI) formation

Corrosion and Protection of Steels in Marine Environments: State-of-the-Art and Emerging Research Trends

Marine corrosion is a very ancient topic, as humankind has, since antiquity, struggled with the corrosiveness of seawater to exploit the countless and essential natural resources of the sea. It is also a broad topic because it combines chemical, biological, and mechanical factors. Among the numerous materials used for marine applications, iron-based alloys (i.e., steels) are essential in various industrial domains such as (of course) the naval industry (ships, submarines, etc.), the energy industry (pipelines, offshore platforms, renewable energy devices, etc.), and buildings (seaport structures, bridges, steel reinforcement in concrete, etc.). Marine corrosion is still an issue to this day, and the recent and necessary development of marine renewable energy devices has motivated innovative research. Currently, complete mastery of corrosion issues is a key aspect in the profitability of produced energy. Simultaneously, the requirements for environmentally friendly anticorrosion methods and processes are clearly expressed. Numerous fundamental and recent advances in marine corrosion and protection of steels, including carbon steel, low alloy steel, and stainless steel, can then be noted. This Special Issue is necessary to acknowledge the recent and sudden increase in the understanding of steel corrosion processes in marine environments and the associated optimization of anticorrosion methods. Last but not least, a large part of our cultural heritage lies at the bottom of seas and oceans, and it will definitely be lost if scientific research does not include current and historical concerns as well

High-glucose feeding of gilthead seabream (Sparus aurata) larvae: effects on molecular and metabolic pathways

Nutritional programming has begun to arouse interest as a novel tool to alter specific metabolic pathways or functions in farmed animals. The aim of the present study was to explore the potential of early glucose stimuli to induce changes in nutrient metabolism of gilthead seabream. Nutritional conditioning was performed by delivering glucose-rich feed at three distinct recurrent periods of larval feeding regime: during first-feeding with rotifers (3 days after hatching, DAH) and mid-feeding with Artemia metanauplii (20DAH) and the beginning of inert diet feeding (30DAH), called the Recurrent treatment (REC). As opposed, the control treatment (CTRL) did not experience any glucose stimuli. At post-larval stage (from 50 to 60DAH), both treatments were challenged with a high-carbohydrate diet (50%). The immediate response to the early stimuli was assessed through gene expression of metabolic markers and by nutrient metabolism using [C-14] tracers. Each dietary stimulus induced metabolic changes on REC larvae, shown by altered expression of some genes, including those involved in glycolysis, and by a different pattern of glucose utilization. However, none of the molecular adaptations (except G6PDH gene) were persistent in the viscera and muscle of challenged post-larvae from REC group. In contrast, the glucose metabolism of challenged REC post-larvae revealed a shift towards a higher catabolism and lower glucose retention in tissues, compared to the CTRL group, suggesting an improvement of glucose oxidation pathways. In addition, the REC group showed a higher bio-conversion of glucose into lipids, indicating enhanced hepatic lipogenesis. The early stimuli did not affect the relative retention or use of amino acids or the growth and survival of challenged fish, up to 60DAH. In summary, although not substantiated at a molecular level, our data reveal that a recurrent high-glucose stimulus during larval stages affects the short-term modulation of pathways for glucose utilization in gilthead seabream. (C) 2015 Elsevier B.V. All rights reserved