Clays as possible catalysts for peptide formation in the prebiotic era.

From the point of view of prebiotic synthesis, clays might have performed functions of concentration, catalysis, and protection of molecules. The degree of polymerization obtained when amino acid adenylates are added to montmorillonite suspensions in water, are much iigher than those obtained by polymerization in the absence of such a clay. In addition, they are of a discrete spectrum, usually multiplies of 6 or 7, and reach values of up to 40 mers. In the absence of clay a continuous spectrum of degrees of polymerization is obtained, and usually up to 4-6 mers only. Copolymerization in the absence of clays yields mostly random copolymers in their presence mostly block copolymers are obtained. Optical density measurements show that after adsorption has taken place on the clay, stacking of its layers occurs. Polymerization starts only after these stacked layers have been formed. The distance between the layers - as measured by X-rays - increase during polymerization, probably because the resulting polymers settle in their interspace, while the adsorption site of the active monomers is at the edges of the clay.     

Clays and other minerals in prebiotic processes

Clays and other minerals have been investigated in context with prebiotic processes, mainly in polymerization of amino acids. It was found that peptides adsorbed on the clay, prior to polymerization, influence the reaction. The ratio between the amount of the peptides adsorbed and that of the clay is important for the yield as well as for the degrees of polymerization obtained. Adsorption prior to reaction produces a certain order in the aggregates of the clay particles which might induce better reaction results. Excess of added peptides disturbs this order and causes lesser degrees of polymerization. In addition to adsorption, clays are also able to occlude between their layers substances out of the environment, up to very high concentrations.     

Clays and other minerals in prebiotic processes

Clays and other minerals have been investigated in context with prebiotic processes, mainly in polymerization of amino acids. It was found that peptides adsorbed on the clay, prior to polymerization, influence the reaction. The ratio between the amount of peptides adsorbed and that of the clay is important for the yield as well as for the degrees of polymerization obtained. Adsorption prior to reaction produces a certain order in the aggregates of the clay particles which might induce better reaction results. Excess of added peptides disturbs this order and causes lesser degrees of polymerization. In addition to adsorption, clays are also able to occlude between their layers substances out of the environment, up to very high concentrations.     

Clays in prebiological chemistry

Summary In this review an attempt is made to highlight the structures and properties of clay that may contribute to a better understanding of the role of clays in chemical evolution. The adsorption of organic molecules on clays has been demonstrated, as has the synthesis of bioorganic monomers in the presence of clays. For instance, amino acids (glycine, aspartic acid, threonine, alanine and others) as well as purines and pyrimidines, have been obtained from CO and NH₃ in the presence of clays at relatively high temperatures (250-325°C). Carbohydrates are also easily derived from formaldehyde at relatively low temperatures (80°C). The oligomerization of biochemical monomers, mediated by clays has also been shown to result in the formation of polymer molecules basic to life. For instance the condensation of amino acyl adenylates at room temperature in the presence of montmorillonite is known to yield polypeptides in discrete ranges of molecular weights with degrees of polymerization up to 56. Clays have also been found to affect the condensation of mononucleotides to oligonucleotides. Although the role of clays in the origin of metabolic pathways has not been demonstrated, it is possible that clays may have played a cooperative role with catalytic peptides in an intermediate stage of prebiological chemistry preceding the emergence of life on this planet.     

The polymerization of amino acid adenylates on sodium-montmorillonite with preadsorbed polypeptides

We studied the spontaneous polymerization of amino acid adenylates on Na-montmorillonite in dilute, neutral suspension, after polypeptides were adsorbed on the clay. This led to the unexpected finding that the degrees of polymerization (DP's) of the oligo- and poly-peptides obtained depended on the amounts of polypeptides that were preadsorbed. Plotting average molecular weights obtained against c-spacings of the clay platelet aggregates which widened as a result of polypeptide addition and adsorption before the polymerization, does not permit an obvious explanation of these observations. The best correlation assigns a role to the fractional occupation of the individual intercalation layers of the polypeptides, as the adsorption increases towards a first complete mono-interlayer, then to an incipient and eventually to a complete double layer on to a third interlayer, after which the clay stacking breaks up. Spacings which correspond to an intermediate occupation of any of the three successive interlayers favor amino acids self-addition to polymers. The opposite is true for nearly empty or filled intercalation layers. We hypothesize and describe, how a catalytic activity may derive from c-spacings that offer adsorption sites for the reagent amino acid adenylate within the peripheral recesses of irregularly stacked clay platelets by bringing the anhydride bonds and neutral amino groups into favorable reaction distances. Moderately filled intercalation spaces may also act as sinks for the newly formed oligomers and facilitate the freeing of reaction sites for the occupation by fresh reagent. The c-spacings required for these mechanisms are the result of the intercalation of the preadsorbed polymer, but similar conditions prevail when polymers are adsorbed as they are generated during polymerization.     

The possible role of clays in prebiotic peptide synthesis

Hypotheses of macromolecule formations during the prebiotic era are described. The presumed role of minerals and clays in these reactions are: concentration of monomers, proton release by ion exchange whenever the reaction demands it, scattering of the charges of the interacting substances, thus allowing such substances to interact, which in the absence of clays repel each other due to their charges. Because of these reasons the polymerization mechanism in the presence of clays is different from that in their absence. While in the absence of clays only free amino acids or peptides can interact with active amino acid anhydrides, giving thus peptides increased by only one unit, in the presence of clays two molecules of amino acid anhydrides can interact, giving a still active peptide anhydride which can interact with another active peptide. Clays catalyze polymerization only in these cases where the amino acid is small enough to enter between the sheets of the clay. Apparently most of the reactions also occur there and not on the surface of the clay. Copolymerization of different pairs of amino acids proceeds selectively in the presence of clay. The relationship between this selecitvity and prebiotic parent proteins is discussed.     

Geology and environmental significance of sediment distributions in an area of the submerged Niagara escarpment,Georgian Bay

The study site covers a spur of the submerged Niagara escarpment and part of the Flowerpot basin of Georgian Bay. Bedrock outcrops occur on islands and shoals but much of the area is covered by glacial till (10–20 m thick). Glaciolacustrine clay occurs in thin patches on the spur; in the deepest parts of the area, however, it is nearly 70 m thick. The distributions of Recent sediments which comprise lag-gravels, sands and silty clays, reflect major postglacial lake level changes in the Huron — Georgian Bay basin.Sediment geochemistry in Georgian Bay is similar to many other parts of the Great Lakes but calcium charbonate levels are lower than expected, except in some deposits of gaciolacustrine clay. There is little evidence of anthropogenic impact in the content of trace metals, although Pb likely includes a portion derived from atmospheric loading; Hg is usually present at very low levels but there are anomalously high values in some deepwater modern muds.In the bottom sediment habitat of modern benthos, the distribution of chironomids seems to reflect silt content. Oligochaetes are least in areas of thin Recent mud or exposed glaciolacustrine clay. Pontoporeia and sculpins are most numerous at depths between 50–110 m. Bottom tracks and other bed marks cover extensive areas of the deepwater lake sediments.     

Improved Yield of High Molecular Weight DNA Coincides with Increased Microbial Diversity Access from Iron Oxide Cemented Sub-Surface Clay Environments

Despite over three decades of progress, extraction of high molecular weight (HMW) DNA from high clay soils or iron oxide cemented clay has remained challenging. HMW DNA is desirable for next generation sequencing as it yields the most comprehensive coverage. Several DNA extraction procedures were compared from samples that exhibit strong nucleic acid adsorption. pH manipulation or use of alternative ion solutions offered no improvement in nucleic acid recovery. Lysis by liquid N₂ grinding in concentrated guanidine followed by concentrated sodium phosphate extraction supported HMW DNA recovery from clays high in iron oxides. DNA recovered using 1 M sodium phosphate buffer (PB) as a competitive desorptive wash was 15.22±2.33 µg DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25 µg DNA/g clay with the Powerlyzer system (MoBio). Increasing PB concentration in the lysis reagent coincided with increasing DNA fragment length during initial extraction. Rarefaction plots of 16S rRNA (V1–V3 region) pyrosequencing from A-horizon and clay soils showed an ∼80% and ∼400% larger accessed diversity compared to the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more operational taxonomic units (OTU) recovered.     

Molecular Modelling of The Mechanism of Action of Organic Clay-Swelling Inhibitors

Abstract

It is well known that the sodium smectite class of clays swells macroscopically in contact with water, whereas under normal conditions the potassium form does not. In recent work using molecular simulation methods, we have provided a quantitative explanation both for the swelling behaviour of sodium smectite clays and the lack of swelling of potassium smectites [1]. In the present paper, we apply similar modelling methods to study the mechanism of inhibition of clay-swelling by a range of organic molecules.

Experimentally, it is known that polyalkylene glycols (polyethers) of intermediate to high relative molecular mass are effective inhibitors of smectite clay swelling. We use a range of atomistic simulation techniques, including Monte Carlo and molecular dynamics, to investigate the interactions between a selection of these compounds, water, and a model smectite clay mineral. These interactions occur by means of organised intercalation of water and organic molecules within the galleries between individual clay layers.

The atomic interaction potentials deployed in this work are not as highly optimised as those used in our clay-cation-water work [1]. Nevertheless, our simulations yield trends and results that are in qualitative and sometimes semi-quantitative agreement with experimental findings on similiar (but not identical) systems. The internal energy of adsorption of simple polyethers per unit mass on the model clay is not significantly different from that for water adsorption; our Monte Carlo studies indicate that entropy is the driving force for the sorption of the simpler organic molecules inside the clay layers: a single long chain polyethylene glycol can displace a large number of water molecules, each of whose translational entropy is greatly enhanced when outside the clay. Hydrophobically modified polyalkylene glycols also enjoy significant van der Waals interactions within the layers which they form within the clay galleries.

In conjunction with experimental studies, our work furnishes valuable insights into the relative effectiveness of the compounds considered and reveals the generic features that high performance clay-swelling inhibitors should possess. For optimal inhibitory activity, these compounds should be reasonably long chain linear organic molecules with localised hydrophobic and hydrophilic regions along the chain. On intercalation of these molecules within the clay layers, the hydrophobic regions provide an effective seal against ingress of water, while the hydrophilic ones enhance the binding of the sodium cations to the clay surface, preventing their hydration and the ensuing clay swelling.     

The mechanism of clay catalyzed polymerization of amino acid adenylates.

Amino acid adenylates were adsorbed on montmorillonite when either the interspatial faces or the edges of the latter were blocked. By this method it could be observed that adsorption of the amino acid adenylates takes place mostly on the planes of the clay. However, for polymerization to take place, the edges of the clay have to be free as well and apparently only these molecules polymerize which are attached to the planes of the clay by their amino groups and to the edges of the clay by their phosphate group. Thus all the charges of the molecules which might produce their repulsion from each other would be neutralized. As a consequence of these attachments polymerization on the clay would take place on its planar sites, but only on those neighboring its edges. The question whether neutralization of charges is also the reason why biochemical substrates have to attach themselves by several points to enzymes and thus make biochemistry fit into the framework of general chemistry, is raised.     

The effect of clays on the oligomerization of HCN

Summary The reaction of 0.1 M HCN and dilute solutions of diaminomaleonitrile (DAMN) at pH 8–9 and 25°C in the presence of suspensions of montmorillonite (bentonite) clays were investigated. Montmorillonite clays inhibit the oligomerization of aqueous solutions of HCN. Yields of colored oligomers, urea, and DAMN, are all diminished by clays, but the rate of loss of cyanide is not significantly decreased. The inhibition of oligomer formation is due to the clay-catalyzed decomposition of DAMN. The absence of strong binding of DAMN to clays was suggested by our failure to detect DAMN when a clay that had been incubated with DAMN was washed with spermidine (6 × 10^–3 g/{ie317-1}). It was established that DAMN does not simply bind to the clays by the observation that the bulk of the radioactivity was recovered from the supernatant in the reaction of¹⁴C-DAMN with montmorillonite. The clay-catalyzed decomposition of DAMN was observed when montmorillonite from two different sources was used and with a variety of homoionic montmorillonites and bentonites. A modification of the established procedure for using the cyanide electrode for cyanide analyses was used to follow the release of HCN from DAMN. This new method can be used in both the acidic and basic pH range and it does not result in the destruction of DAMN by the reagents used for the analysis. Quantitative analyses of the reaction solution from the clay-catalyzed decomposition of DAMN revealed the formation of 1–2 equivalents of HCN per mole of DAMN. The possible significance of these clay-catalyzed reactions in chemical evolution is discussed. Chemical Evolution 35: For the previous papers in this series see Ferris, J P. and Joshi, P.C., (1978), Science 201, 361–362; Ferris, J.P., Narang, R.S., Newton, T.A. and Rao, V.R., (1979), J. Org. Chem. 44, 1273–1278; Ferris, J.P. (1979), Science 203, 1135–1136; Ferris, J.P. and Joshi, P.C., (1979), J. Org. Chem. 44, 2133–2137     

Thermodynamics of peptide bond formation at clay mineral surfaces

Summary The possibility of surface catalysed condensation of unsubstituted amino acids on kaolinite in aqueous systems at elevated temperatures was investigated; no evidence of clay catalysed polycondensation has been found. The thermodynamic feasibility of the hypothetical lysine/dilysine condensation reaction in the temperature-range up to 90° C was evaluated for a range of experimental conditions by the combination of measured free energies of lysine/dilysine cation exchange on kaolinite and on montmorillonite, and free energies for the analogous condensation reaction in homogeneous solution. The results indicate that, in spite of the high selectivity of the clays for the adsorption of cation dimers from dilute solutions, the thermodynamic barrier to the surface condensation of unsubstituted amino acids on clay minerals in aqueous systems up to 90° C is not lower than it is in homogeneous solution.     

Insecticidal Activity of the Toxins from Bacillus thuringiensis subspecies kurstaki and tenebrionis Adsorbed and Bound on Pure and Soil Clays

The release of transgenic plants and microorganisms expressing truncated genes from various subspecies of Bacillus thuringiensis that encode active insecticidal toxins rather than inactive protoxins could result in the accumulation of these active proteins in soil, especially when bound on clays and other soil particles. Toxins from B. thuringiensis subsp. kurstaki and B. thuringiensis subsp. tenebrionis, either free or adsorbed at equilibrium or bound on pure clay minerals (montmorillonite or kaolinite) or on the clay size fraction of soil, were toxic to larvae of the tobacco hornworm (Manduca sexta) and the Colorado potato beetle (Leptinotarsa decemlineata), respectively. The 50% lethal concentrations (LC(inf50)) of free toxins from B. thuringiensis subsp. kurstaki were higher than those of both bound and adsorbed complexes of these toxins with clays, indicating that adsorption and binding of these toxins on clays increase their toxicity in diet bioassays. The LC(inf50) of the toxin from B. thuringiensis subsp. tenebrionis that was either free or adsorbed on montmorillonite were comparable, whereas the toxin bound on this clay had higher LC(inf50) and the toxin bound on kaolinite had lower LC(inf50) than when adsorbed on this clay. Results obtained with the clay size fraction separated from unamended soil or soil amended with montmorillonite or kaolinite were similar to those obtained with the respective pure clay minerals. Therefore, insecticidal activity of these toxins is retained and sometimes enhanced by adsorption and binding on clays.     

Adsorption of reovirus to clay minerals: effects of cation-exchange capacity, cation saturation, and surface area.

The adsorption of reovirus to clay minerals has been reported by several investigators, but the mechanisms defining this association have been studied only minimally. The purpose of this investigation was to elucidate the mechanisms involved with this interaction. More reovirus type 3 was adsorbed, in both distilled and synthetic estuarine water, by low concentrations of montmorillonite than by comparable concentrations of kaolinite containing a mixed complement of cations on the exchange complex. Adsorption to the clays was essentially immediate and was correlated with the cation-exchange capacity of the clays, indicating that adsorption was primarily to negatively charged sites on the clays. Adsorption was greater with low concentrations of clays in estuarine water than in distilled water, as the higher ionic strength of the estuarine water reduced the electrokinetic potential of both clay and virus particles. The addition of cations (as chloride salts) to distilled water enhanced adsorption, with divalent cations being more effective than monovalent cations and 10(-2) M resulting in more adsorption than 10(-3) M. Potassium ions suppressed reovirus adsorption to montmorillonite, probably by collapsing the clay lattices and preventing the expression of the interlayer-derived cation-exchange capacity. More virus was adsorbed by montmorillonite made homoionic to various mono-, di-, and trivalent cations (except by montmorillonite homoionic to potassium) than by comparable concentrations of kaolinite homoionic to the same cations. The sequence of the amount of adsorption to homoionic montmorillonite was Al greater than Ca greater than Mg greater than Na greater than K; the sequence of adsorption to kaolinite was Na greater than Al greater than Ca greater than Mg greater than K. The constant partition-type adsorption isotherms obtained when the clay concentration was maintained constant and the virus concentration was varied indicated that a fixed proportion of the added virus population was adsorbed, regardless of the concentration of infectious particles. A heterogeneity within the reovirus population was indicated.     

Adsorption of reovirus to clay minerals: effects of cation-exchange capacity, cation saturation, and surface area

The adsorption of reovirus to clay minerals has been reported by several investigators, but the mechanisms defining this association have been studied only minimally. The purpose of this investigation was to elucidate the mechanisms involved with this interaction. More reovirus type 3 was adsorbed, in both distilled and synthetic estuarine water, by low concentrations of montmorillonite than by comparable concentrations of kaolinite containing a mixed complement of cations on the exchange complex. Adsorption to the clays was essentially immediate and was correlated with the cation-exchange capacity of the clays, indicating that adsorption was primarily to negatively charged sites on the clays. Adsorption was greater with low concentrations of clays in estuarine water than in distilled water, as the higher ionic strength of the estuarine water reduced the electrokinetic potential of both clay and virus particles. The addition of cations (as chloride salts) to distilled water enhanced adsorption, with divalent cations being more effective than monovalent cations and 10(-2) M resulting in more adsorption than 10(-3) M. Potassium ions suppressed reovirus adsorption to montmorillonite, probably by collapsing the clay lattices and preventing the expression of the interlayer-derived cation-exchange capacity. More virus was adsorbed by montmorillonite made homoionic to various mono-, di-, and trivalent cations (except by montmorillonite homoionic to potassium) than by comparable concentrations of kaolinite homoionic to the same cations. The sequence of the amount of adsorption to homoionic montmorillonite was Al greater than Ca greater than Mg greater than Na greater than K; the sequence of adsorption to kaolinite was Na greater than Al greater than Ca greater than Mg greater than K. The constant partition-type adsorption isotherms obtained when the clay concentration was maintained constant and the virus concentration was varied indicated that a fixed proportion of the added virus population was adsorbed, regardless of the concentration of infectious particles. A heterogeneity within the reovirus population was indicated.     

Influence of suspended clay on phosphorus uptake by periphyton

We investigated the effect of suspended clay upon the phosphorus uptake rate exhibited by lotic periphyton communities. Suspended inorganic clays and periphyton are common to aquatic environments, and both can strongly influence physical and chemical water conditions. We used replicated artificial stream channels to test the prediction that suspended clay particles would affect the uptake of soluble reactive phosphorus (SRP) by periphyton. Commercially available kaolinite and bentonite clays were characterized for their aqueous suspension behavior and affinities for SRP. Periphyton was grown in a recirculating stream system and subjected to simultaneous suspended clay and SRP additions. SRP removal from solution, both in the presence and absence of suspended clays, was used to quantify SRP uptake parameters by periphyton. Clay type and concentrations of 20, 80, and 200 mg l⁻¹ had no significant effect upon SRP uptake rate exhibited by periphyton during three 90-min experiments. Less than 1% of SRP removal was attributable to the suspended clay load or artificial stream construction materials, based on clay isotherm data and material sorption studies, indicating that 99% of SRP removal was attributable to biotic uptake. Removal of SRP (as KH₂PO₄) was described by a first-order equation with rate constants ranging between 0.02 and 0.14 min⁻¹. Our results suggest that high turbidity conditions caused by suspended mineral clays have little immediate effect upon SRP removal from the water column by periphyton. Handling editor: D. Ryder     

A review of conditions affecting the radiolysis due to40K on nucleic acid bases and their derivatives adsorbed on clay minerals: Implications in prebiotic chemistry

This paper describes the possible effects of ionizing radiation arising from long-lived soluble radionuclides within clays, in particular⁴⁰K, at the epoch of the emergence of life on Earth. The free dispersion of soluble radionuclides constitutes an effectivein situ irradiation mechanism that might have acted upon adsorbed nucleic bases and their derivatives on clays, inducing chemical changes on these organic molecules. Several types of well documented reactions for radiolysis of nucleic acid bases and their derivatives are known, even at low doses (i.e., 0.1 Gy). For example, estimates with a dose rate calculated from⁴⁰K from deep sea clays at 3.8 Ga ago, indicates that over a period of 1000 years the amount of organic material transformated is 1.8 × 10^–7 moles/kg-clay.Although ionizing radiation may also induce synthetic reactions with prebiological interest, all in all these considerations indicate that nucleic acid bases and their derivatives adsorbed on clays were exposed for long periods to degradation conditions. Such situation promotes decomposition of organic molecules rather than protection of them and enhancement of further polymerization, as it has been usually taken for granted.     

Adsorption of Adenine, Cytosine, Thymine, and Uracil on Sulfide-Modified Montmorillonite: FT-IR, M?ssbauer and EPR Spectroscopy and X-Ray Diffractometry Studies

In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe²⁺ to Fe³⁺, thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine????cytosine?>?thymine?>?uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na₂S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH⁺ or NH ₂ ⁺ groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g????2 increased probably because the oxidation of Fe²⁺ to Fe³⁺ by nucleic acid bases and intensity of the line g?=?4.1 increased due to the interaction of Fe³⁺ with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe²⁺ doublet area of the clays due to the reaction of nucleic acid bases with Fe²⁺.     

Extracellular enzyme-clay mineral complexes: Enzyme adsorption, alteration of enzyme activity, and protection from photodegradation

Enzymes released extracellularly by micro-organisms have major functions in nutrient acquisition and organic matter degradation. Clay particles, common in many surface waters, can modify enzyme activity. Clay minerals are known to form aggregates with organic molecules, and the formation of enzyme-clay complexes could alter the level of activity. Montmorillonite clay and clay extracted from Elledge Lake (Tuscaloosa, Alabama) basin soil were combined with alkaline phosphatase, glucosidase, protease, and xylosidase solutions to assess adsorption and the effect of this adsorption on enzyme activity. Adsorption to Elledge Lake basin clay decreased alkaline phosphatase activity, and adsorption to montmorillonite was observed for all four enzymes with reductions in enzyme activities. Adsorption of substrate onto clay surfaces resulted in a concentration effect and increased enzyme activity associated with the particles. When enzyme-clay complexes were exposed to natural sunlight there was a decrease in enzyme activity, but this decrease was usually not significantly different from the adsorption only treatment. The formation of enzyme-clay complexes may serve to protect the enzymes from natural in situ photodegradation. The results indicate the complex interactive effects adsorption of enzymes to clay particles can have on the availability and capability of hydrolysis – reduction of enzyme reactivity, storage attached to clay particles with changes in transport and distribution, and protection from photodegradation.     

Role of the Interchangeable Cations on the Sorption of Fumaric and Succinic Acids on Montmorillonite and its Relevance in Prebiotic Chemistry

It has been proposed that clays could have served as key factors in promoting the increase in complexity of organic matter in primitive terrestrial and extraterrestrial environments. The aim of this work is to study the adsorption–desorption of two dicarboxylic acids, fumaric and succinic acids, onto clay minerals (sodium and iron montmorillonite). These two acids may have played a role in prebiotic chemistry, and in extant biochemistry, they constitute an important redox couple (e.g. in Krebs cycle) in extant biochemistry. Smectite clays might have played a key role in the origins of life. The effect of pH on sorption has been tested; the analysis was performed by UV–vis and FTIR-ATR spectroscopy, X-ray diffraction and X-ray fluorescence. The results show that chemisorption is the main responsible of the adsorption processes among the dicarboxylic acids and clays. The role of the ion, present in the clay, is fundamental in the adsorption processes of dicarboxylic acids. These ions (sodium and iron) were selected due to their relevance on the geochemical environments that possibly existed into the primitive Earth. Different mechanisms are proposed to explain the sorption of dicarboxylic acids in the clay. In this work, we propose the formation of complexes among metal cations in the clays and dicarboxylic acids. The organic complexes were probably formed in the prebiotic environments enabling chemical processes, prior to the appearance of life. Thus, the data presented here are relevant to the origin of life studies.