Oligomerization of glycine and alanine on metal(II) octacynaomolybdate(IV): role of double metal cyanides in prebiotic chemistry

Role of metal(ii) hexacyanocobaltate(iii) surface chemistry for prebiotic peptides synthesis

Double metal cyanide (DMC), a heterogeneous catalyst, provides a surface for the polymerization of amino acids. Based on the hypothesis, the present study is designed to evaluate favorable environmental conditions for the chemical evolution and origin of life, such as the effects of temperature and time on the oligomerization of glycine and alanine on metal(ii) hexacyanocobaltate(iii), MHCCo. A series of MHCCo complexes were synthesized and characterized by XRD and FT-IR techniques. The effect of outer metal ions present in the MHCCo complexes on the condensation of glycine and alanine was studied. Our results revealed that Zn2+ ions in the outer sphere showed high catalytic activity compared to other metal ions in the outer sphere. Manganese(ii) hexacyanocobaltate(iii) (MnHCCo), iron(ii) hexacyanocobaltate(iii) (FeHCCo), nickel(ii) hexacyanocobaltate(iii) (NiHCCo) complexes condense the glycine up to trimer and the alanine up to dimer. At the same time, ZnHCCo showed the most valuable catalytic properties that change glycine into a tetramer and alanine into a dimer with a high yield at 90 °C after four weeks. ZnHCCo showed high catalytic activity because of its high surface area compared to other MHCCo complexes. High-Performance Liquid Chromatography (HPLC) and Electron Spray Ionization-Mass Spectroscopy (ESI-MS) techniques were used to confirm the oligomer products of glycine and alanine formed on MHCCo complexes. The results also exposed the catalytic role of MHCCo for the oligomerization of biomolecules, thus supporting chemical evolution.

From Catalysis of Evolution to Evolution of Catalysis

The mystery of the origins of life is one of the most difficult yet intriguing challenges to which humanity has grappled. How did biopolymers emerge in the absence of enzymes (evolved biocatalysts), and how did long-lasting chemical evolution find a path to the highly selective complex biology that we observe today? In this paper, we discuss a chemical framework that explores the very roots of catalysis, demonstrating how standard catalytic activity based on chemical and physical principles can evolve into complex machineries. We provide several examples of how prebiotic catalysis by small molecules can be exploited to facilitate polymerization, which in biology has transformed the nature of catalysis. Thus, catalysis evolved, and evolution was catalyzed, during the transformation of prebiotic chemistry to biochemistry. Traditionally, a catalyst is defined as a substance that (i) speeds up a chemical reaction by lowering activation energy through different chemical mechanisms and (ii) is not consumed during the course of the reaction. However, considering prebiotic chemistry, which involved a highly diverse chemical space (i.e., high number of potential reactants and products) and constantly changing environment that lacked highly sophisticated catalytic machinery, we stress here that a more primitive, broader definition should be considered. Here, we consider a catalyst as any chemical species that lowers activation energy. We further discuss various demonstrations of how simple prebiotic molecules such as hydroxy acids and mercaptoacids promote the formation of peptide bonds via energetically favored exchange reactions. Even though the small molecules are partially regenerated and partially retained within the resulting oligomers, these prebiotic catalysts fulfill their primary role. Catalysis by metal ions and in complex chemical mixtures is also highlighted. We underline how chemical evolution is primarily dictated by kinetics rather than thermodynamics and demonstrate a novel concept to support this notion. Moreover, we propose a new perspective on the role of water in prebiotic catalysis. The role of water as simply a "medium" obscures its importance as an active participant in the chemistry of life, specifically as a very efficient catalyst and as a participant in many chemical transformations. Here we highlight the unusual contribution of water to increasing complexification over the course of chemical evolution. We discuss possible pathways by which prebiotic catalysis promoted chemical selection and complexification. Taken together, this Account draws a connection line between prebiotic catalysis and contemporary biocatalysis and demonstrates that the fundamental elements of chemical catalysis are embedded within today's biocatalysts. This Account illustrates how the evolution of catalysis was intertwined with chemical evolution from the very beginning.

The Effect of Goethites on the Polymerization of Glycine and Alanine Under Prebiotic Chemistry Conditions

After pre concentration of monomers, polymerization is the second most important step for molecular evolution. The formation of peptides is an important issue for prebiotic chemistry and consequently for the origin of life. In this work, goethite was synthesized by two different routes, named goethite-I and goethite-II. Although both samples are goethite, Far-FT-IR spectroscopy and EPR spectroscopy showed differences between them, and these differences had an effect on the polymerization of glycine and alanine. For the amino acid polymerization, three protocols were used, that resembled prebiotic Earth conditions: a) amino acid plus goethite were mixed and heated at 90 °C for 10 days in solid state, b) a wet impregnation of the amino acid in the goethite, with subsequent heating at 90 °C for 10 days in solid state, and c) 10 wet/dry cycles each one for 24 h at 90 °C. Experiments with glycine plus goethite-II, using protocols B and C, produced only Gly-Gly. In addition, for the C protocol the amount of Gly-Gly synthesized was 3 times higher than the amount of Ala-Ala. Goethite-I presented a decrease in the EPR signal, when it was submitted to the protocols with and without amino acids. It is probable the decrease in the intensity of the EPR signal was due to a decrease in the imperfections of the mineral. For all protocols the mixture of alanine plus goethite-I or goethite-II produced c(Ala-Ala). However, for wet/dry cycles, protocol C presented higher yields (p < 0.05). In addition, Ala-Ala was produced using protocols A and C. The c(Ala-Ala) formation fitted a zero-order kinetic equation model. The surface areas of goethite-I and goethite-II were 35 m² g^-1 and 37 m² g^-1, respectively. Thermal analysis indicated that the mineral changes the thermal behavior of the amino acids. The main reactions for the thermal decomposition of glycine were deamination and dehydration and for alanine was deamination.

Transition metals enhance prebiotic depsipeptide oligomerization reactions involving histidine

Biochemistry exhibits an intense dependence on metals. Here we show that during dry-down reactions, zinc and a few other transition metals increase the yield of long histidine-containing depsipeptides, which contain both ester and amide linkages. Our results suggest that interactions of proto-peptides with metal ions influenced early chemical evolution.

Transition metals enhance prebiotic proto-peptide oligomerization reactions through direct association with histidine.

Quantitative Analysis of Glycine Oligomerization by Ion-Pair Chromatography

This paper describes a method for the quantitative analysis of mixtures of glycine and its oligomers by ion-pair high-performance liquid chromatography (IP-HPLC), with a particular focus on applications in origins-of-life research. We demonstrate the identification of glycine oligomers (Gly _n ) up to 14 residues long-the approximate detectable limit of their solubility in water-and measurement of the concentration of these species in the product mixture of an oligomerization reaction. The molar response factors for higher oligomers of glycine-which are impractical to obtain as pure samples-are extrapolated from direct analysis of pure standards of n = 3-6, which established a clear linear trend. We compare and contrast our method to those in previous reports with respect to accuracy and practicality. While the data reported here are specific to the analysis of oligomers of glycine, the approach should be applicable to the design of methods for the analysis of oligomerization of other amino acids.

Thermal Condensation of Glycine and Alanine on Metal Ferrite Surface: Primitive Peptide Bond Formation Scenario

The amino acid condensation reaction on a heterogeneous mineral surface has been regarded as one of the important pathways for peptide bond formation. Keeping this in view, we have studied the oligomerization of the simple amino acids, glycine and alanine, on nickel ferrite (NiFe₂O₄), cobalt ferrite (CoFe₂O₄), copper ferrite (CuFe₂O₄), zinc ferrite (ZnFe₂O₄), and manganese ferrite (MnFe₂O₄) nanoparticles surfaces, in the temperature range from 50-120 °C for 1-35 days, without applying any wetting/drying cycles. Among the metal ferrites tested for their catalytic activity, NiFe₂O₄ produced the highest yield of products by oligomerizing glycine to the trimer level and alanine to the dimer level, whereas MnFe₂O₄ was the least efficient catalyst, producing the lowest yield of products, as well as shorter oligomers of amino acids under the same set of experimental conditions. It produced primarily diketopiperazine (Ala) with a trace amount of alanine dimer from alanine condensation, while glycine was oligomerized to the dimer level. The trend in product formation is in accordance with the surface area of the minerals used. A temperature as low as 50 °C can even favor peptide bond formation in the present study, which is important in the sense that the condensation process is highly feasible without any sort of localized heat that may originate from volcanoes or hydrothermal vents. However, at a high temperature of 120 °C, anhydrides of glycine and alanine formation are favored, while the optimum temperature for the highest yield of product formation was found to be 90 °C.

Formamide-based synthesis of nucleobases by metal(II) octacyanomolybdate(IV): implication in prebiotic chemistry

We propose that double metal cyanides that formed in primeval seas might have played a vital role in chemical evolution and the origin of life. An array of metal octacyanomolybdates (MOCMos) has been synthesized, and their role as catalyst in the formation of nucleobases from formamide has been studied. Formamide, a hydrolysis product of HCN, was taken as starting material for the formation of nucleobases. Recent studies support the presence of formamide on some celestial bodies. Metal octacyanomolybdates, MOCMos (M = Mn, Fe, Co, Ni, Cu, Zn, Cd), are found to be highly efficient catalysts in the conversion of formamide into different nucleobases. Neat formamide is converted to purine, 4(3H)-pyrimidinone, cytosine, adenine, 9-(hydroxyacetyl)-purine, and thymine in good yield when using MOCMos. The products formed were characterized by high-performance liquid chromatography and electrospray ionization mass spectrometry techniques. The results of our study show that insoluble double metal cyanides might have acted as efficient catalysts in the synthesis of various biologically important compounds (e.g., purines, pyrimidines) under primeval seas on Earth or elsewhere in our solar system.