María Colín-García

Adsorption of HCN onto sodium montmorillonite dependent on the pH as a component to chemical evolution

The aim of this work is to study the behaviour of hydrogen cyanide (HCN) adsorbed onto mineral surfaces (sodium montmorillonite, a clay mineral) in different pH environments as a possible prebiotic process for complexation of organics. Our experimental results show that specific sites on the surface of the clay increased the concentration of HCN molecules dependent on the pH values. Moreover, this adsorption can occur through physical and chemical interactions enhanced by the channel structure of the sodium montmorillonite. The three-dimensional channelling structure of the clay accumulates the organics, hindering the releasing (desorption) of the organic molecules. A molecular model developed here also confirms the role of the pH as a regulating factor in the adsorption of HCN onto the inorganic surfaces and the possibility for further reactions forming more complex molecules, as an abiotic mechanism important in prebiotic chemical evolution processes. Received 12 February 2014, accepted 27 March 2014, first published online 12 May 2014

Ultraviolet irradiation of glycine in presence of pyrite as a model of chemical evolution: an experimental and molecular modelling approach

In this work, the molecular interaction of the amino acid glycine and the mineral pyrite was performed to gain insight into the potential role of the mineral as a precursor of chemical complexity in the presence of ultraviolet (UV) radiation. Glycine samples were self-assembled on pyrite with and without exposure to UV radiation and subsequently characterized by scanning electron microscopy, infrared spectroscopy (with the second-derivative method), and AM1 and PM3 semi-empirical molecular computational simulations. In this work, our molecular modelling results suggest that pyrite acts as a template for self-assembly of glycine, and it is a potential catalyst for the glycine dimerization of relevance in interstellar space and ancient Earth conditions. A change in the structural complexity of glycine from the α to its γ polymorph when irradiated with UV radiation can be a condition for chemical evolution towards living forms.

Detection of Peptidic Sequences in the Ancient Acidic Sediments of Río Tinto, Spain

Biomarkers are molecules that are produced by or can be associated with biological activities. They can be used as tracers that give us an idea of the ancient biological communities that produced them, the paleoenvironmental conditions where they lived, or the mechanism involved in their transformation and preservation. As a consequence, the preservation potential of molecules over time depends largely on their nature, but also on the conditions of the environment, which controls the decomposition kinetics. In this context, proteins and nucleic acids, which are biomolecules bearing biological information, are among the most labile molecules. In this research, we report the presence of short-chained peptides obtained from extracts of ferruginous sedimentary deposits that have been produced under the acidic and oxidizing solutions of Río Tinto, Spain. These preliminary results go against the paradigmatic idea that considers the acidic and oxidizing environments inappropriate for the preservation of molecular information.

Radiation-induced catalysis of fatty acids adsorbed onto clay minerals

We studied the behavior of small fatty (acetic acid) and dicarboxylic acids (succinic and malonic acids) adsorbed onto Na+-montmorillonite (a clay mineral) and exposed to gamma radiation. A decarboxylation reaction was found to predominate when the clay was present. This preferential synthesis promoted the formation of a compound with one less carbon atom than its target compound. In the system without clay, dimerization was the predominate outcome following radiolysis.

Radiolysis of succinic acid and its ammonium salt in aqueous solution: relevance in chemical evolution

This research aims to contribute in determining the stability of ammonium succinate and succinic acid in an oxygen-free aqueous medium and exposed to a high radiation field. Both molecules are readily formed in prebiotic experiments and are essential in chemical evolution processes as starting materials for more complex molecules’ formation. Several products were detected, including some N-containing compounds in the ammonium salt experiments. Their formation can be explained via the attack of water radiolysis products. Abstraction and dimerization reactions were the most important in these systems. The decomposition increased with the irradiation dose, giving rise to biologically compounds relevant for chemical evolution processes.

Computer simulation and experimental self-assembly of irradiated glycine amino acid under magnetic fields: Its possible significance in prebiotic chemistry

Ionizing radiation may have played a relevant role in chemical reactions for prebiotic biomolecule formation on ancient Earth. Environmental conditions such as the presence of water and magnetic fields were possibly relevant in the formation of organic compounds such as amino acids. ATR-FTIR, Raman, EPR and X-ray spectroscopies provide valuable information about molecular organization of different glycine polymorphs under static magnetic fields. γ-glycine polymorph formation increases in irradiated samples interacting with static magnetic fields. The increase in γ-glycine polymorph agrees with the computer simulations. The AM1 semi-empirical simulations show a change in the catalyst behavior and dipole moment values in α and γ-glycine interaction with the static magnetic field. The simulated crystal lattice energy in α-glycine is also affected by the free radicals under the magnetic field, which decreases its stability. Therefore, solid α and γ-glycine containing free radicals under static magnetic fields might have affected the prebiotic scenario on ancient Earth by causing the oligomerization of glycine in prebiotic reactions.

Deposition of Carbon Nanotube Films on Polyamide and Polypropylene Substrates: A Computer Simulation Approach

In this work we study hydroxylated carbon nanotube (CNT) assembly on polyamide (PA) and polypropylene (PP) polymers activated by UV radiation from a theoretical and experimental perspective. Molecular computer simulation was done to understand the stable conformations and bulk properties (molecular dynamics) of the polymers before and after exposure to UV radiation at the molecular level. Our experiments suggest that PA presents more -OH active groups, producing a more hydrophilic surface, whereas PP exhibits less potential UV activation. These results suggest that it is possible a facile covalent functionalization method to tune organic polymer surface properties through SWCNT anchoring for nanotechnological applications requiring defined surface roughness and chemical functionality on inexpensive polymers.

Heterogeneous radiolysis of urea. Implications in astrobiology and prebiotic chemistry

Abstract Urea is an organic molecule present in most living organisms. Historically, it was the first organic molecule synthesized in the laboratory. In prebiotic chemistry, urea readily forms in different laboratory simulations using different energy sources. Furthermore, the role of solid surfaces, particularly minerals, might have been crucial to increase the complexity of the organic matter which may have led to the subsequent emergence of life on Earth. In this work, the radiolysis of urea in presence of a clay is studied to determine to what extent the mineral surfaces influence the decomposition of organics. The results indicate that urea is relatively stable to ionizing radiation in aqueous solutions and up to 20 kGy no decomposition is observed. Moreover, the presence of sodium montmorillonite, by a mechanism until now unknown, affects the radiolytic behavior and urea remains in the heterogeneous solution without a change in concentration even at very high doses (140 kGy). These results indicate that solids could have protected some organics, like urea, from degradation enabling them to remain in the environment on the primitive Earth. Graphical Abstract

Piezoelectricidad y ferroelectricidad en biomateriales

En este articulo se presenta una revision de los conceptos de piezoelectricidad y ferroelectricidad, asi como sus aplicaciones en materiales complejos e hibridos organico-inorganicos mediante el uso de las tecnicas de microscopia de fuerza atomica (AFM) y de fuerza de piezorespuesta (PFM). Aunque este tipo de estudios son escasos en las areas biologicas, se sugiere el uso de estas tecnicas para analizar las propiedades de piezorespuesta en peptidos debido a su relevancia en las reacciones prebioticaspero y en el diseno de maquinas nanomoleculares.

Radiation chemistry approach to the study of ice analogs

The aim of this work is to study the chemistry of the irradiation of frozen solutions of HCN. This compound has been detected in comets and other icy bodies. The CN group might have made its first appearance in the early stages of chemical evolution. Therefore, is behavior under irradiation at low temperature is relevant for chemical evolution studies and icy bodies.