An experimental and numerical model of the behavior of cytosine in aqueous solution under gamma radiation. Relevance in prebiotic chemistry.

Cytosine is an essential chemical molecule in living systems, such as DNA and RNA, it is essential in astrobiology to study how it behaves under probable primitive conditions. We looked at how cytosine broke down in aqueous solutions exposed to high radiation levels to learn more about how stable it might have been on the early Earth. We conducted various types of analysis, such as ultraviolet-visible spectroscopy and high-pressure liquid chromatography.

Numerical modeling vs experiment of formic acid and formate ion behavior under gamma radiation at several pH values: Implications on prebiotic chemistry.

Formic acid is consistently produced and detected in prebiotic chemistry experiments, constituting a precursor of many carboxylic acids and amino acids. Its behavior with exposure to gamma radiation varies with the pH and solution concentration. This work aimed to model different environmental conditions for formic acid under ionizing radiation using a system of coupled differential equations based on chemical kinetics.

Alkaline saline lakes: A chemical evolution experiment evaluating the stability of formaldehyde in an aqueous saline environment.

Formaldehyde condensation in the presence of a mineral catalyst and under alkaline conditions is considered to be a "messy" chemical system due to its dependence on the complex chemical equilibrium between the reaction intermediates, which has a significant impact on the final products. This chemical system is extremely important in prebiotic chemistry and has been proposed as a potential pathway for carbohydrate formation in the early Earth. Saline and soda lakes are alkaline systems that could concentrate and accumulate a wide variety of ions (such as phosphate) and clay minerals, which can catalyze prebiotic chemical reactions.

Gamma irradiation of adenine and guanine adsorbed into hectorite and attapulgite.

This study focuses on the radiolysis (up to 36 kGy) of guanine and adenine (nitrogenous bases) adsorbed in hectorite and attapulgite to highlight the potential role of clays as protective agents against ionizing radiation in prebiotic processes. In this framework, the study investigated the nitrogenous bases' behavior in two types of systems: a) aqueous suspension of adenine-clay systems and b) guanine-clay systems in the solid state. This research utilized spectroscopic and chromatographic techniques for its analytical purposes.

Stability of DL-Glyceraldehyde under Simulated Hydrothermal Conditions: Synthesis of Sugar-like Compounds in an Iron(III)-Oxide-Hydroxide-Rich Environment under Acidic Conditions.

Researchers have suggested that the condensation of low-molecular-weight aldehydes under basic conditions (e.g., pH > 11) is the prebiotic reaction responsible for the abiotic formation of carbohydrates.

Histidine Self-assembly and Stability on Mineral Surfaces as a Model of Prebiotic Chemical Evolution: An Experimental and Computational Approach.

The abiotic synthesis of histidine under experimental prebiotic conditions has proven to be chemically promising and plausible. Within this context, the present results suggest that histidine amino acid may function as a simple prebiotic catalyst able to enhance amino acid polymerization. This work describes an experimental and computational approach to the self-assembly and stabilization of DL-histidine on mineral surfaces using antigorite ((Mg, Fe)SiO(OH)), pyrite (FeS), and aragonite (CaCO) as representative minerals of prebiotic scenarios, such as meteorites, and subaerial and submarine hydrothermal systems.

Computer and Experimental Simulation of Alloxazine Synthesis from Gamma Irradiation of Amino Acids on Iceland Spar: A Prebiotic Chemistry Perspective.

On ancient Earth, environmental conditions favored prebiotic chemical reactions. In the Archean, some molecules with conjugated rings might have been synthesized, displaying structural stability in the Archean in the presence of ionizing radiation and hydration-dehydration events. Additionally, it is suggested that on ancient Earth, calcite was a common mineral promoting organic compound synthesis.

Adenine Adsorbed onto Montmorillonite Exposed to Ionizing Radiation: Essays on Prebiotic Chemistry.

Most adsorption and radiolysis experiments related to prebiotic chemistry studies are performed in distilled water or sodium chloride solutions. However, distilled water and sodium chloride solutions do not represent the composition of the primitive seas of Earth. In this work, an artificial seawater with ion abundances Mg > Ca >> Na ≈ K and SO >> Cl was used, one that is different from the average composition of seawater today.

Solid adenine and seawater salts exposed to gamma radiation: An FT-IR and EPR spectroscopy analysis for prebiotic chemistry.

Solids of adenine obtained from distilled water and seawater lyophilized solutions were γ irradiated at a 94.52 kGy dose. Results indicate that pure solid adenine had a low degradation rate, likewise the solid containing seawater salts.

Salinity Effects on the Adsorption of Nucleic Acid Compounds on Na-Montmorillonite: a Prebiotic Chemistry Experiment.

Any proposed model of Earth's primitive environments requires a combination of geochemical variables. Many experiments are prepared in aqueous solutions and in the presence of minerals. However, most sorption experiments are performed in distilled water, and just a few in seawater analogues, mostly inconsistent with a representative primitive ocean model.

Effects of temperature during the irradiation of calcium carbonate.

Calcium carbonate received gamma irradiation at different doses (0-309kGy) and temperature regimes (77-298K) to study the effects of irradiation temperature. The changes were followed by EPR spectroscopy. We observed the formation of a composite EPR spectrum, even at low radiation doses and temperature.

Calcium carbonate as a possible dosimeter for high irradiation doses.

The aim of this work is to analyze the interactions of 5MeV electron beam radiation and a 290MeV/u Carbon beam with calcium carbonate (powder) at 298K and at different irradiation doses, for the potential use of calcium carbonate as a high-dose dosimeter. The irradiation doses with the electron beam were from 0.015 to 9MGy, and with Carbon beam from 1.

Characterization of selective antibacterial peptides by polarity index.

In the recent decades, antibacterial peptides have occupied a strategic position for pharmaceutical drug applications and became subject of intense research activities since they are used to strengthen the immune system of all living organisms by protecting them from pathogenic bacteria. This work proposes a simple and easy statistical/computational method through a peptide polarity index measure by which an antibacterial peptide subgroup can be efficiently identified, that is, characterized by a high toxicity to bacterial membranes but presents a low toxicity to mammal cells. These peptides also have the feature not to adopt to an alpha-helicoidal structure in aqueous solution.

The gamma ray response of alanine film dosimeters at low temperatures.

The response of alanine film EPR dosimeters was studied for low temperature gamma irradiation conditions (77-293 K) in the dose interval from 6.3 to 80 kGy. It was found that the response of the dosimeter decreases with decreased irradiation temperature and saturates at lower doses for lower irradiation temperatures.

Organics produced by irradiation of frozen and liquid HCN solutions: implications for chemical evolution studies.

Hydrogen cyanide (HCN), an important precursor of organic compounds, is widely present in extraterrestrial environments. HCN is also readily synthesized in prebiotic simulation experiments. To gain insight into the radiation chemistry of one of the most important and highly versatile constituents of cometary ices, we examined the behavior of over-irradiated frozen and liquid HCN solutions under ionizing radiation.

Prebiotic thermal polymerization of crystals of amino acids via the diketopiperazine reaction.

In this work, we continue our studies on the thermal prebiotic oligomerization of amino acids. The next step is to consider all four types of electromagnetic interactions that our model may admit. In addition, only the polymerization of amino acids via the formation of diketopiperazine, which arises from the cyclodehydration of two amino acids, will be considered.

Optical absorption and thermoluminescence in single NaCl:Cu crystals exposed to 60Co and UV light.

Optical absorption (OA) and thermally stimulated luminescence measurements were performed on NaCl:Cu+(0.04 and 0.08%) crystals blocks grown by the Czochralski technique.

Sites of adsorption of adenine, uracil, and their corresponding derivatives on sodium montmorillonite.

Clay minerals are considered important to chemical evolution processes due to their properties, ancient origin, and wide distribution. To extend the knowledge of their role in the prebiotic epoch, the adsorption sites of adenine, adenosine, AMP, ADP, ATP, Poly A, uracil, uridine, UMP, UDP, UTP and Poly U on sodium montmorillonite are investigated. X-ray diffraction, ultraviolet and infrared spectroscopy studies indicate that these molecules distribute into the interlamellar channel and the edge of the clay crystals.

The behavior of single crystals of NaCl: Ca2+, Mn2+ exposed to gamma rays.

The behavior of single crystals of NaCl: Ca(2+), Mn(2+) exposed to gamma rays was explored for its potential usage as a dosimeter. The study was focused to the effect of dose and dose rate. The crystals were analyzed using thermoluminescence (TL).

Iron salts in solid state and in frozen solutions as dosimeters for low irradiation temperatures.

The aim of this work is to study the irradiation of iron salts in solid state (heptahydrated ferrous sulfate) and in frozen acid solutions. The study is focused on finding their possible use as dosimeters for low temperature irradiations and high doses. The analysis of the samples was made by UV-visible and Mössbauer spectroscopies.

Dependence of irradiation temperature in the response of iron salts.

A potential dosimeter based on aqueous frozen solutions and solid-state salt are presented for the evaluation of the energy transferred during the interaction of high-energy radiation with matter at low temperature. The foundation of these dosimeters, both the solid state and the frozen solutions, is based on the measurement of the change of the iron oxidation state. The systems were irradiated with gamma radiation at different doses (up to 10 MGy), and at different temperatures (from 77 to 298 K).

Dependence of thermoluminescence response of calcium sulphate activated by dysprosium on the temperature irradiation.

Radiation dosimetry is a very important issue in space research and in experiments that try to simulate chemical processes that may occur in cometary nucleus, interstellar grains, and other extraterrestrial environments, due to their irradiation by cosmic rays. The temperature effect is an important factor that has not been considered in many of these experiments. In this work, this effect was studied in TLD dosimeters exposed to gamma rays.

Evaluation of the dosimetric response for CaSO4:Dy at low temperature.

Homemade solid state CaSO4:Dy detectors were tested to evaluate their response to gamma radiation at liquid nitrogen temperature (77 K). The dosemeters were irradiated with doses between 12 and 1071 Gy. For this study these dosemeters were exposed to gamma rays with a dose rate of 1.

Behavior of adenine in Na-montmorillonite exposed to gamma radiation: implications to chemical evolution studies.

Adenine is an important compound in biological systems, such as genetic and energy utilization processes. Adenine is readily formed in prebiotic conditions. Its synthesis and stability in environmental conditions are of paramount importance in chemical evolution processes.

Biased polymers in the origin of life.

We delve into the study of a Markov chain formalism applied to the thermal prebiotic oligomerization of amino acids. We find for the case of only two types of electromagnetic interactions, that the steady state attainment by the Markov chain is a built in mechanism limiting the expected variability in sequences in a population of polymers. Such result may be of importance as it makes more accessible the replication of a minimal chemical machinery compatible with life.