Prebiotic Material Research Articles

Molecular asymmetry in extraterrestrial chemistry: Insights from a pristine meteorite

The nonracemic amino acids of meteorites provide the only natural example of molecular asymmetry measured so far outside the biosphere. Because extant life depends on chiral homogeneity for the structure and function of biopolymers, the study of these meteoritic compounds may offer insights into the establishment of prebiotic attributes in chemical evolution as well as the origin of terrestrial homochirality. However, all efforts to understand the origin, distribution, and scope of these amino acids' enantiomeric excesses (ee) have been frustrated by the ready exposure of meteorites to terrestrial contaminants and the ubiquitous homochirality of such contamination. We have analyzed the soluble organic composition of a carbonaceous meteorite from Antarctica that was collected and stored under controlled conditions, largely escaped terrestrial contamination and offers an exceptionally pristine sample of prebiotic material. Analyses of the meteorite diastereomeric amino acids alloisoleucine and isoleucine allowed us to show that their likely precursor molecules, the aldehydes, also carried a sizable molecular asymmetry of up to 14% in the asteroidal parent body. Aldehydes are widespread and abundant interstellar molecules; that they came to be present, survived, and evolved in the solar system carrying ee gives support to the idea that biomolecular traits such as chiral asymmetry could have been seeded in abiotic chemistry ahead of life.

Peptide Nucleic Acids and the Origin of Life

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Synthesis, characterization and hybridization studies of new nucleo‐γ‐peptides based on diaminobutyric acid

In the present work, we report the synthesis and the characterization of a new chiral nucleoaminoacid, in which a diaminobutyric moiety is connected to the DNA nucleobase by an amidic bond, and its oligomerization to give the corresponding nucleo-gamma-peptide. The ability of this synthetic polymer to bind complementary DNA was studied in order to explore its possible use in antigene/antisense or diagnostic applications. Our interest in the presented DNA analogue was also supported by the importance of gamma-aminoacid-containing compounds in natural products of biological activity and by the known stability of gamma-peptides to enzymatic degradation. Furthermore, our work could contribute to the study of the role of nucleopeptides as prebiotic material in a PNA world that could successively lead to the actual DNA/RNA/protein world, as recently assumed.

Prebiotic materials from on and off the early Earth

One of the greatest puzzles of all time is how did life arise? It has been universally presumed that life arose in a soup rich in carbon compounds, but from where did these organic molecules come? In this article, I will review proposed terrestrial sources of prebiotic organic molecules, such as Miller-Urey synthesis (including how they would depend on the oxidation state of the atmosphere) and hydrothermal vents and also input from space. While the former is perhaps better known and more commonly taught in school, we now know that comet and asteroid dust deliver tons of organics to the Earth every day, therefore this flux of reduced carbon from space probably also played a role in making the Earth habitable. We will compare and contrast the types and abundances of organics from on and off the Earth given standard assumptions. Perhaps each process provided specific compounds (amino acids, sugars, amphiphiles) that were directly related to the origin or early evolution of life. In any case, whether planetary, nebular or interstellar, we will consider how one might attempt to distinguish between abiotic organic molecules from actual signs of life as part of a robotic search for life in the Solar System.

Soy oligosaccharides in vitro fermentation characteristics and its effect on caecal microorganisms of young broiler chickens

An in vitro trial was conducted to evaluate the fermentation characteristics of soybean meal oligosaccharides (SMO) and changes in the caecal contents microbial community of broiler chickens as affected by SMO by using cumulative gas production and a PCR/DGGE technique. An in vivo trial aimed to study the effect of SMO on the caecal contents lactic acid bacteria (LAB) population and caecal wall attached microorganisms by means of a real-time PCR technique and scanning electron microscope, when SMO was used in the diet of broiler chickens during the first 2 weeks of post-hatch. In vitro trial results indicated SMO produced 245.7 ml gas/g DM, 261.8 mg acetic acid/g DM, 187.2 mg propionic acid/g DM and 155.2 mg butyric acid/g DM. In vivo experimental results showed that dietary SMO increased visible microbial populations attached on caecal walls and increased the population of a group of lactic acid bacteria (genera of Lactobacillus, Pediococcus, Weissella and Leuconostoc) in the caecal contents of young broiler chickens (P<0.05). In conclusion, SMO does show promise for use as a product which may promote competitive exclusion of potential pathogens. SMO may therefore, be a suitable substitute for dietary antibiotics in young broiler chickens in the future. As a potential prebiotic material, the selective stimulation of SMO on LAB could not be certified by the current experimental results and needs to be further studied.

Educators learn the latest about small bodies in the solar system

The past decade has heralded the advance of both scholarship and exploration of small bodies in the solar system. Once relegated to subsidiary status, asteroids, comets, and now Kuiper Belt objects (KBOs) have come into their own as planetary scientists have become aware of their importance for understanding the origins of the solar system. Because these objects are believed to be debris remaining from the earliest periods of planet formation, they may offer clues to the physical conditions and architecture of the early solar system.The key role impact processes have played in the evolution of the Earth and other planets has also been recognized. Earth‐crossing objects have caused mass extinctions in the past, and comets are now believed to have delivered significant amounts of volatiles and prebiotic material to the inner solar system. NASA has supported this blossoming field of study by sending several missions to comets and asteroids, and by establishing special programs to study them.

Mars atmospheric oxidant sensor (MAOS): an in-situ heterogeneous chemistry analysis

We describe a chemometric array sensor, the Mars atmospheric oxidant sensor (MAOS, pronounced “mouse”) that is designed to measure the oxidation rate of thin films on the martian surface. We select films that are sensitive to particular types of oxidants, that represent key elements in the martian soil, or that emulate prebiotic materials. Concern that naturally arising martian oxidants may have destroyed evidence of ancient life on Mars was raised by the Viking mission in the 1970s. The possibility that oxidants may limit the viability of biological habitats is particularly timely in the light of recent suggestions of contemporary flowing water on Mars. By controlling the temperature of the films, as well as their exposure to dust and ultraviolet light, MAOS will discriminate among leading hypotheses for oxidant production. MAOS weighs 55 g , fits in a 6×7×2 cm 3 envelope, and used 250 mW power. Much of the enabling technology was developed for the MOx experiment, lost on the Russian Mars ’96 mission.

Template-directed polynucleotide synthesis on mineral surfaces.

Ferric hydroxide, a plausible prebiotic material, strongly adsorbs polynucleotides. We show that adsorption on ferric hydroxide and on several other minerals has no effect, under the conditions studied, on the template-directed oligomerization of guanylic acid on polycytidylic acid.

Association of nucleotides with homoionic clays

The binding of nucleotides to homoionic clays is studied as a possible mechanism for the concentration and catalysis of biological or prebiotic materials on the prebiotic earth. Samples of radioactively labeled adenosine and thymidine nucleotides were mixed in solutions with bentonite, kaolinite or Dowex-50 particles in which all exchangeable sites were occupied by Na, Mg, Ca, Mn, Fe, Cu or Zn ions. The binding of nucleotides to homoionic clays is observed, with adenosine nucleotides favored over thymidine, bentonite as the best absorber, and greater binding to clays homoionic in transition metal ions. Results indicate that the oligomerization of nucleotides may be possible by this mechanism, however difficulties in nucleotide variability and base pairing may arise due to the observed preference for purines at the adsorption sites.

Synthesis of uracil and thymine under simulated prebiotic conditions

Evaporation and mild heating of solutions of beta-alanine and urea in the presence of clay minerals leads to the formation of 5,6-dihydrouracil (DHU). Ultraviolet irradiation of DHU in the presence of clay minerals and water vapor leads to the synthesis of uracil. Addition of acetate to this system results in the synthesis of thymine. The entire pathway could plausibly occur in pools subject to cycles of dehydration and rehydration and would result in the formation of significant concentrations of uracil and thymine from indisputably prebiotic materials.