Showing papers in "Origins of Life and Evolution of Biospheres in 2014"
TL;DR: Despite the ability of aqueous two-phase systems to effectively concentrate RNA, there is a high rate of RNA exchange between phases in dextran/polyethylene glycol ATPS and ATP/poly-L-lysine coacervate droplets, rendering these systems ineffective as model protocells.
Abstract: Compartmentalization in a prebiotic setting is an important aspect of early cell formation and is crucial for the development of an artificial protocell system that effectively couples genotype and phenotype. Aqueous two-phase systems (ATPSs) and complex coacer- vates are phase separation phenomena that lead to the selective partitioning of biomolecules and have recently been proposed as membrane-free protocell models. We show in this study through fluorescence recovery after photobleaching (FRAP) microscopy that despite the ability of such systems to effectively concentrate RNA, there is a high rate of RNA exchange between phases in dextran/polyethylene glycol ATPS and ATP/poly-L-lysine coacervate droplets. In contrast to fatty acid vesicles, these systems would not allow effective segregation and consequent evolution of RNA, thus rendering these systems ineffective as model protocells.
95 citations
TL;DR: An alternative approach to guide research into the origins of life is discussed, one that focuses on "paradoxes”, pairs of statements, both grounded in theory and observation, that (taken together) suggest that the “origins problem” cannot be solved.
Abstract: The “Open Questions” framework reflects an understandable frustration of many who study “origins” that much of current research into the “origins problem” seems to be no different conceptually from research formulated a half century ago by Orgel, Miller, and other heroes of modern prebiotic chemistry. Discussed here is an alternative approach to guide research into the origins of life, one that focuses on “paradoxes”, pairs of statements, both grounded in theory and observation, that (taken together) suggest that the “origins problem” cannot be solved. A substantial amount of ink has been consumed by efforts to define life, without consensus. This motivates many of us experimentalists to consciously avoid the “definition trap”. We do so by noting that states of matter can be offered as exemplars for “not life” without controversy, as can states of matter that everyone agrees constitute “life”. The consensus fails to define the boundary between these two. Nevertheless, much productive discussion can follow without needing to identify “the” distinguishing feature that represents “the” unique difference between any pair of states offered. This is illustrated by a recent report on the limits of organic life in the Solar System, whose authors declined to demarcate the difference between life and non-life (Baross et al. 2007; Benner et al. 2004). Of course, under the language and theory used by modern science to describe states of matter, pairs of “life” and “not-life” exemplars agreed by consensus certainly appear different, and in very many ways, no matter what those exemplars are. This means that the emergence of an indisputably living state (no matter how chosen) from any indisputably non-living state (no matter how chosen) appears to require a “lengthy pathway consisting of many stages” (Szostak 2012). It is, of course, an open question as to whether this appearance truly means that life actually can originate only via a lengthy pathway, or whether this appearance simply reflects incomplete and/or incorrect Orig Life Evol Biosph (2014) 44:339–343 DOI 10.1007/s11084-014-9379-0
48 citations
TL;DR: Crowding might have enhanced the capabilities of protocells for evolutionary innovation through the creation of extended neutral networks in the fitness landscape.
Abstract: The environment of protocells might have been crowded with small molecules and functional and non-specific polymers. In addition to altering conformational equilibria, affecting reaction rates and changing the structure and activity of water, crowding might have enhanced the capabilities of protocells for evolutionary innovation through the creation of extended neutral networks in the fitness landscape.
40 citations
TL;DR: Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation.
Abstract: The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150 °C for 336 h under dry, wet, and dry–wet conditions to clarify the mechanism. Approximately 13.9 % of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction.
39 citations
TL;DR: The results clearly support the hypothesis that autocatalytic sets can be evolvable, and that this might even be an expected property of such sets.
Abstract: We provide a formal but visually clear example of how a set of minimal necessary conditions for evolvability of autocatalytic sets is satisfied in a simple model of chemical reaction systems. Furthermore, we show how these conditions can be captured and analyzed with RAF theory, and how the results can be generalized with a somewhat more elaborate example. Finally, we argue that our results clearly support the hypothesis that autocatalytic sets can be evolvable, and that this might even be an expected property of such sets.
36 citations
TL;DR: Crowding will occur in the spaces between Muscovite mica sheets, which has many advantages as a site for life’s origins.
Abstract: Molecular crowding increases the likelihood that life as we know it would emerge. In confined spaces, diffusion distances are shorter, and chemical reactions produce fewer and more regular products. Crowding will occur in the spaces between Muscovite mica sheets, which has many advantages as a site for life's origins.
35 citations
TL;DR: In this article, the authors studied the origin and escape of catastrophically outgassed volatiles (H2O, CO2) from exomoons with Earth-like densities and masses of 0.1, 0.5 and 1 M
Abstract: We study the origin and escape of catastrophically outgassed volatiles (H2O, CO2) from exomoons with Earth-like densities and masses of 0.1, 0.5 and 1 M
⊕ orbiting an extra-solar gas giant inside the habitable zone of a young active solar-like star. We apply a radiation absorption and hydrodynamic upper atmosphere model to the three studied exomoon cases. We model the escape of hydrogen and dragged dissociation products O and C during the activity saturation phase of the young host star. Because the soft X-ray and EUV radiation of the young host star may be up to ~100 times higher compared to today’s solar value during the first 100 Myr after the system’s origin, an exomoon with a mass < 0.25 M
⊕ located in the HZ may not be able to keep an atmosphere because of its low gravity. Depending on the spectral type and XUV activity evolution of the host star, exomoons with masses between ~0.25 and 0.5 M
⊕ may evolve to Mars-like habitats. More massive bodies with masses >0.5 M
⊕, however, may evolve to habitats that are a mixture of Mars-like and Earth-analogue habitats, so that life may originate and evolve at the exomoon’s surface.
30 citations
TL;DR: This communication proposes a more reasonable [GADV]-protein world hypothesis or GADV hypothesis, suggesting that life originated from the protein world, which was formed by pseudo-replication of [G ADV]-proteins.
Abstract: RNA world hypothesis is widely accepted still now, as an idea by which the origin of life might be explained. But, there are many weak points in the hypothesis. In contrast, I have proposed a more reasonable [GADV]-protein world hypothesis or GADV hypothesis, suggesting that life originated from the protein world, which was formed by pseudo-replication of [GADV]-proteins. In this communication, I will discuss about the origin of life from the point of view of the GADV hypothesis.
28 citations
TL;DR: Examining the ability of four extremophilic bacteria from Archaea and Bacteria domains to resist to space environment by exposing them to extreme conditions of temperature, UV radiation, desiccation coupled to low pressure generated in a Mars’ conditions simulator showed that H. hispanica and G. thermantarcticus were resistant to desICcation and low pressure.
Abstract: In this work we investigated the ability of four extremophilic bacteria from Archaea and Bacteria domains to resist to space environment by exposing them to extreme conditions of temperature, UV radiation, desiccation coupled to low pressure generated in a Mars’ conditions simulator All the investigated extremophilic strains (namely Sulfolobus solfataricus, Haloterrigena hispanica, Thermotoga neapolitana and Geobacillus thermantarcticus) showed a good resistance to the simulation of the temperature variation in the space; on the other hand irradiation with UV at 254 nm affected only slightly the growth of H hispanica, G thermantarcticus and S solfataricus; finally exposition to Mars simulated condition showed that H hispanica and G thermantarcticus were resistant to desiccation and low pressure
27 citations
TL;DR: The presence of mineral analogues provided a protective effect, preserving survivability and integrity of DNA and photosynthetic pigments, as revealed by testing colony-forming abilities, performing PCR-based assays and using confocal laser scanning microscopy.
Abstract: In the context of future exposure missions in Low Earth Orbit and possibly on the Moon, two desert strains of the cyanobacterium Chroococcidiopsis, strains CCMEE 029 and 057, mixed or not with a lunar mineral analogue, were exposed to fractionated fluencies of UVC and polychromatic UV (200–400 nm) and to space vacuum. These experiments were carried out within the framework of the BIOMEX (BIOlogy and Mars EXperiment) project, which aims at broadening our knowledge of mineral-microorganism interaction and the stability/degradation of their macromolecules when exposed to space and simulated Martian conditions. The presence of mineral analogues provided a protective effect, preserving survivability and integrity of DNA and photosynthetic pigments, as revealed by testing colony-forming abilities, performing PCR-based assays and using confocal laser scanning microscopy. In particular, DNA and pigments were still detectable after 500 kJ/m2 of polychromatic UV and space vacuum (10−4 Pa), corresponding to conditions expected during one-year exposure in Low Earth Orbit on board the EXPOSE-R2 platform in the presence of 0.1 % Neutral Density (ND) filter. After exposure to high UV fluencies (800 MJ/m2) in the presence of minerals, however, altered fluorescence emission spectrum of the photosynthetic pigments were detected, whereas DNA was still amplified by PCR. The present paper considers the implications of such findings for the detection of biosignatures in extraterrestrial conditions and for putative future lunar missions.
22 citations
TL;DR: The findings confirm that when 3 L-Ser units are present in the cluster, the photolytic decomposition of Trp is enantiomerically selective, and the hypothesis that homochirality in gas-phase Ser clusters promotes the enantiomersic enrichment of other amino acids via en antiomer-selective photolysis with linearly polarized light is confirmed.
Abstract: Photostability of cold gas-phase tryptophan (Trp) enantiomers in L-serine (L-Ser) clusters at 8 K as a model for interstellar molecular clouds was examined using a tandem mass spectrometer containing a cold ion trap to investigate the hypothesis that homochirality in gas-phase Ser clusters promotes the enantiomeric enrichment of other amino acids via enantiomer-selective photolysis with linearly polarized light In the UV excitation of heterochiral H+ (L-Ser) 3(D-Trp), the CO2-eliminated product in the cluster was observed In contrast, the photodissociation mass spectrum of homochiral H+(L-Ser)3(L-Trp) showed that photolysis of amino acids in the cluster did not occur due to the evaporation of L-Ser molecules In the spectra of the homochiral H+(L-Ser) (L-Trp) and heterochiral H+(L-Ser) (D-Trp), the evaporation of L-Ser was the primary reaction pathway, and no difference between the L- and D-enantiomers was observed The findings confirm that when 3 L-Ser units are present in the cluster, the photolytic decomposition of Trp is enantiomerically selective
TL;DR: In this paper, the results of the first laboratory impact experiments were reported, showing that sugar molecules can not only survive but also become more complex during impact delivery to the planetary bodies.
Abstract: Sugars of extraterrestrial origin have been observed in the interstellar medium (ISM), in at least one comet spectrum, and in several carbonaceous chondritic meteorites that have been recovered from the surface of the Earth. The origins of these sugars within the meteorites have been debated. To explore the possibility that sugars could be generated during shock events, this paper reports on the results of the first laboratory impact experiments wherein glycolaldehyde, found in the ISM, as well as glycolaldehyde mixed with montmorillonite clay, have been subjected to reverberated shocks from ~5 to >25 GPa. New biologically relevant molecules, including threose, erythrose and ethylene glycol, were identified in the resulting samples. These results show that sugar molecules can not only survive but also become more complex during impact delivery to planetary bodies.
TL;DR: It is shown that some terpenoids, such as cholesterol and α, ω-dipolar carotenoids reinforce lipid membranes by measuring the water permeability of unilamellar vesicles, and a hypothetical pathway from C1 or C2 units to ‘primitive’ membranes and that from ‘Primitive” membranes to archaeal lipids are presented.
Abstract: Terpenoids have an essential function in present-day cellular membranes, either as membrane reinforcers in Eucarya and Bacteria or as principal membrane constituents in Archaea. We have shown that some terpenoids, such as cholesterol and α, ω-dipolar carotenoids reinforce lipid membranes by measuring the water permeability of unilamellar vesicles. It was possible to arrange the known membrane terpenoids in a ‘phylogenetic’ sequence, and a retrograde analysis led us to conceive that single-chain polyprenyl phosphates might have been ‘primitive’ membrane constituents. By using an optical microscopy, we have observed that polyprenyl phosphates containing 15 to 30 C-atoms form giant vesicles in water in a wide pH range. The addition of 10 % molar of some polyprenols to polyprenyl phosphate vesicles have been shown to reduce the water permeability of membranes even more efficiently than the equimolecular addition of cholesterol. A ‘prebiotic’ synthesis of C10 and C15 prenols from C5 monoprenols was achieved in the presence of a montmorillonite clay. Hypothetical pathway from C1 or C2 units to ‘primitive’ membranes and that from ‘primitive’ membranes to archaeal lipids are presented.
TL;DR: It is proposed that the prototRNA dimer-directed mechanism of protein synthesis and encoding promotes a sink dynamics that corresponds to the driving ‘force’ for the fixation of the supporting metabolic pathways.
Abstract: The self-referential genetic encoding starts with glycine and serine, in the realm of one-carbon units of metabolism. It is proposed that the prototRNA dimer-directed mechanism of protein synthesis and encoding promotes a sink dynamics that corresponds to the driving ‘force’ for the fixation of the supporting metabolic pathways. A succession of processes is delineated, ending up in reproduction, which accomplished the function of reinforcing the protein synthesis metabolic sink mechanism.
TL;DR: The answer is positive, although I am too well aware that the term “conceivable” does not mean that this something is easily to be performed experimentally, as no living system exists on Earth which does not obey this principle.
Abstract: It is argued that closed, cell-like compartments, may have existed in prebiotic time, showing a simplified metabolism which was bringing about a primitive form of stationary state- a kind of homeostasis. The autopoietic primitive cell can be taken as an example and there are preliminary experimental data supporting the possible existence of this primitive form of cell activity. The genetic code permits, among other things, the continuous self-reproduction of proteins; enzymic proteins permit the synthesis of nucleic acids, and in this way there is a perfect recycling between the two most important classes of biopolymers in our life. On the other hand, the genetic code is a complex machinery, which cannot be posed at the very early time of the origin of life. And the question then arises, whether some form of alternative beginning, prior to the genetic code, would have been possible: and this is the core of the question asked. Is something with the flavor of early life conceivable, prior to the genetic code? My answer is positive, although I am too well aware that the term “conceivable” does not mean that this something is easily to be performed experimentally. To illustrate my answer, I would first go back to the operational description of cellular life as given by the theory of autopoiesis. Accordingly, a living cell is an open system capable of self-maintenance, due to a process of internal self-regeneration of the components, all within a boundary which is itself product from within. This is a universal code, valid not only for a cell, but for any living macroscopic entity, as no living system exists on Earth which does not obey this principle. In this definition (or better operational description) there is no mention of DNA or genetic code. I added in that definition the term “open system”-which is not present in the primary literature (Varela, et al., 1974) to make clear that every living system is indeed an open system-without this addition, it may seem that with autopoiesis we are dealing with a perpetuum mobile, against the second principle of thermodynamics. Now consider the following figure (Fig. 1). It represents in a very schematic form a cell, as an open system, with a semipermeable membrane constituted by the chemical S, which permits the entrance of the nutrient A and the elimination of the decay product P. A is transformed inside the cell into S by a chemical reaction characterized by kgen, and S can be transformed into P by the reaction kdec. The two reactions actually may represent two entire families of reaction, in the sense that one can envisage several A and several S and several P.
TL;DR: Comparisons with later solar flare events will be attempted on the basis of the record and the consequences of an event of comparable magnitude to the 1859 set of flares will be discussed.
Abstract: The beginning of September 1859 was the occasion of the first and unique observation of a giant solar white light flare, auroral displays were observed at low latitudes and geomagnetic observatories recorded exceptional storms. This paper reviews the impact of the event on the earth system with a special emphasis on living processes using the historical record and current scientific analysis. The data used includes reports from the telegraph operators, mortality and morbidity records, proxies as agricultural production. Comparisons with later solar flare events will be attempted on the basis of the record and the consequences of an event of comparable magnitude to the 1859 set of flares will be discussed.
TL;DR: In this protein-centered scenario, the emergent coevolution of uncoded peptides, metabolic cofactors and oligoribonucleotides was primarily optimized for system-supporting catalytic capabilities arising from nonribosomal peptide synthesis and nonreplicative ribonucleotide polymerization, which in turn incorporated other reactive micromolecular organics as vitamins and cofactor into composite macromolecules colloid films and microspheres.
Abstract: Self-replicating molecules, in particular RNA, have long been assumed as key to origins of life on Earth This notion, however, is not very secure since the reduction of life’s complexity to self-replication alone relies on thermodynamically untenable assumptions Alternative, earlier hypotheses about peptide-dominated colloid self-assembly should be revived Such macromolecular conglomerates presumably existed in a dynamic equilibrium between confluent growth in sessile films and microspheres detached in turbulent suspension The first organic syntheses may have been driven by mineral-assisted photoactivation at terrestrial geothermal fields, allowing photo-dependent heterotrophic origins of life Inherently endowed with rudimentary catalyst activities, mineral-associated organic microstructures can have evolved adaptively toward cooperative ‘protolife’ communities, in which ‘protoplasmic continuity’ was maintained throughout a graded series of ‘proto-biofilms’, ‘protoorganisms’ and ‘protocells’ toward modern life The proneness of organic microspheres to merge back into the bulk of sessile films by spontaneous fusion can have made large populations promiscuous from the beginning, which was important for the speed of collective evolution early on In this protein-centered scenario, the emergent coevolution of uncoded peptides, metabolic cofactors and oligoribonucleotides was primarily optimized for system-supporting catalytic capabilities arising from nonribosomal peptide synthesis and nonreplicative ribonucleotide polymerization, which in turn incorporated other reactive micromolecular organics as vitamins and cofactors into composite macromolecular colloid films and microspheres Template-dependent replication and gene-encoded protein synthesis emerged as secondary means for further optimization of overall efficieny later on Eventually, Darwinian speciation of cell-like lineages commenced after minimal gene sets had been bundled in transmissible genomes from multigenomic protoorganisms
TL;DR: A continuous, evolutionary path that connects nascent biochemistry with simple, membrane-bound oligopeptides, ion channels and, further, membrane proteins capable of energy transduction and utilization of energy for active transport is mapped.
Abstract: Primordial metabolism co-evolved with the earliest membrane peptides to produce more environmentally fit progeny. Here, we map a continuous, evolutionary path that connects nascent biochemistry with simple, membrane-bound oligopeptides, ion channels and, further, membrane proteins capable of energy transduction and utilization of energy for active transport.
TL;DR: This communication has proposed the idea that protein 0th-order structures or specific amino acid compositions would mediate the transfer from random process to formation of ordered sequences, after formation of double-stranded genes.
Abstract: Only random processes should occur on the primitive Earth. In contrast, many ordered sequences are synthesized according to genetic information on the present Earth. In this communication, I have proposed an idea that protein 0th-order structures or specific amino acid compositions would mediate the transfer from random process to formation of ordered sequences, after formation of double-stranded genes.
TL;DR: The developed methods are suitable to determine if microbes exist at the International Space Station altitude and distinguish between microbial DNA and inorganic compounds after staining the aerogel with the DNA-specific fluorescence dye SYBR green I.
Abstract: We have proposed an experiment (the Tanpopo mission) to capture microbes on the Japan Experimental Module of the International Space Station. An ultra low-density silica aerogel will be exposed to space for more than 1 year. After retrieving the aerogel, particle tracks and particles found in it will be visualized by fluorescence microscopy after staining it with a DNA-specific fluorescence dye. In preparation for this study, we simulated particle trapping in an aerogel so that methods could be developed to visualize the particles and their tracks. During the Tanpopo mission, particles that have an orbital velocity of ~8 km/s are expected to collide with the aerogel. To simulate these collisions, we shot Deinococcus radiodurans-containing Lucentite particles into the aerogel from a two-stage light-gas gun (acceleration 4.2 km/s). The shapes of the captured particles, and their tracks and entrance holes were recorded with a microscope/camera system for further analysis. The size distribution of the captured particles was smaller than the original distribution, suggesting that the particles had fragmented. We were able to distinguish between microbial DNA and inorganic compounds after staining the aerogel with the DNA-specific fluorescence dye SYBR green I as the fluorescence of the stained DNA and the autofluorescence of the inorganic particles decay at different rates. The developed methods are suitable to determine if microbes exist at the International Space Station altitude.
TL;DR: It is proposed that the prebiotic ordering of nucleic acid and peptide sequences was a cooperative process in which nearly random populations of both kinds of polymers went through a codependent series of self-organisation events that simultaneously refined not only the accuracy of genetic replication and coding but also the functional specificity of protein catalysts, especially nascent aminoacyl-tRNA synthetase “urzymes”.
Abstract: It is proposed that the prebiotic ordering of nucleic acid and peptide sequences was a cooperative process in which nearly random populations of both kinds of polymers went through a codependent series of self-organisation events that simultaneously refined not only the accuracy of genetic replication and coding but also the functional specificity of protein catalysts, especially nascent aminoacyl-tRNA synthetase "urzymes".
TL;DR: It is shown that the in situ formation of vesicles in a solution containing macromolecular solutes, permits to obtain filled vesicle which are overcrowded of those solutes and therefore viable for complex biochemical reactions.
Abstract: We emphasize here that, in considering the initial prebiotic reactions, it is fundamental to take into consideration the critical threshold concentration, in particular when talking about self-replication and initial metabolism. It is also shown that the in situ formation of vesicles in a solution containing macromolecular solutes, permits to obtain filled vesicles which are overcrowded of those solutes and therefore viable for complex biochemical reactions.
TL;DR: Halophilic organisms are having adaptations to extreme salinity, the majority of them being Archaean, which have the ability to grow at extremely high salt concentrations, (from 3 % to 35 %).
Abstract: Halophilic organisms are having adaptations to extreme salinity, the majority of them being Archaean, which have the ability to grow at extremely high salt concentrations, (from 3 % to 35 %). Level of salinity causes natural fluctuations in the halophilic populations that inhabit this particular habitat, raising problems in maintaining homeostasis of the osmotic pressure. Samples such as salt and water taken from Turda Salt Mine were analyzed in order to identify the eco-physiological bacterial groups. Considering the number of bacteria of each eco-physiological group, the bacterial indicators of salt quality (BISQ) were calculated and studied for each sample. The phosphatase, catalase and dehydrogenases enzymatic activities were quantitatively determined and the enzymatic indicators of salt quality (EISQ) were calculated. Bacterial isolates were analyzed using 16S rRNA gene sequence analysis. Universal bacterial primers, targeting the consensus region of the bacterial 16S rRNA gene were used. Analysis of a large fragment, of 1499 bp was performed to improve discrimination at the species level.
TL;DR: Two main problems of replication in the early stages of evolution are discussed: the problem of exponentially large number of conformational degrees of freedom and theproblem of enumeration of variants.
Abstract: Two main problems of replication in the early stages of evolution are discussed: the problem of exponentially large number of conformational degrees of freedom and the problem of enumeration of variants.
TL;DR: Two perspectives on code origin are provided by carrying out simulations of code-sequence coevolution in finite populations with the aim of examining how the standard genetic code may have evolved from more primitive code(s) encoding a small number of amino acids.
Abstract: The origin of a genetic code made it possible to create ordered sequences of amino acids. In this article we provide two perspectives on code origin by carrying out simulations of code-sequence coevolution in finite populations with the aim of examining how the standard genetic code may have evolved from more primitive code(s) encoding a small number of amino acids. We determine the efficacy of the physico-chemical hypothesis of code origin in the absence and presence of horizontal gene transfer (HGT) by allowing a diverse collection of code-sequence sets to compete with each other. We find that in the absence of horizontal gene transfer, natural selection between competing codes distinguished by differences in the degree of physico-chemical optimization is unable to explain the structure of the standard genetic code. However, for certain probabilities of the horizontal transfer events, a universal code emerges having a structure that is consistent with the standard genetic code.
TL;DR: In the discussed chemical pathway, the reaction is found to be totally exothermic and barrier less giving rise to a high probability of acrylonitrile formation in Interstellar space.
Abstract: Acrylonitrile (CH2CHCN) was first detected in dense molecular cloud SgrB2. The synthesis of this interstellar molecule is reported to be quite difficult. Therefore, in the present work an attempt has been made to explore the possibility of formation of acrylonitrile from some simple molecules and radicals detected in interstellar space by radical-radical interaction scheme, both in the gas phase and in the icy grains. All calculations are performed using quantum chemical methods with density functional theory (DFT) at the B3LYP/6-311G (d,p) level and Moller-Plesset perturbation theory at the MP2/6-311G (d,p) level. In the discussed chemical pathway, the reaction is found to be totally exothermic and barrier less giving rise to a high probability of acrylonitrile formation in Interstellar space.
TL;DR: SecYEG is synthesized by expressing the corresponding gene in vitro to study the process of functionalization of the cell membrane.
Abstract: The cell membrane has many indispensable functions for sustaining cell alive besides a role as merely outer envelope. The most of such functions are implemented by membrane embedded proteins that are emerged through the membrane integration machinery, SecYEG translocon. Here, we synthesized SecYEG by expressing the corresponding gene in vitro to study the process of functionalization of the cell membrane.
TL;DR: The structural and functional characteristics of Jeewanu suggests that in possible prebiotic atmosphere photosy nergistic collaboration of non-linear processes at mesoscopic level established autocatalytic pathways on mineral surfaces by selforganisation and self recognition and led to emergence of similar earliest energy transducing supramolecular assemblies which might have given rise to common universal ancestor on the earth or elsewhere.
Abstract: Sunlight exposed sterilised aqueous mixture of ammonium molybdate, diammonium hydrogen phosphate, biological minerals and formaldehyde showed photochemical formation of self-sustaining biomimetic protocell-like supramolecular assemblies “Jeewanu” (Bahadur and Ranganayaki J Brit Interplanet Soc 23:813–829 1970). The structural and functional characteristics of Jeewanu suggests that in possible prebiotic atmosphere photosy nergistic collaboration of non-linear processes at mesoscopic level established autocatalytic pathways on mineral surfaces by selforganisation and self recognition and led to emergence of similar earliest energy transducing supramolecular assemblies which might have given rise to common universal ancestor on the earth or elsewhere.
TL;DR: A 2-dimensional cellular automata model was constructed to investigate the emergence of biological cell formation, which incorporated a looped membrane and a membrane-bound information system (akin to a genetic code and gene expression system) and did not completely clarify all the necessary and sufficient conditions for biological cell self-organization.
Abstract: Understanding the generalized mechanisms of cell self-assembly is fundamental for applications in various fields, such as mass producing molecular machines in nanotechnology. Thus, the details of real cellular reaction networks and the necessary conditions for self-organized cells must be elucidated. We constructed a 2-dimensional cellular automata model to investigate the emergence of biological cell formation, which incorporated a looped membrane and a membrane-bound information system (akin to a genetic code and gene expression system). In particular, with an artificial reaction system coupled with a thermal system, the simultaneous formation of a looped membrane and an inner reaction process resulted in a more stable structure. These double structures inspired the primitive biological cell formation process from chemical evolution stage. With a model to simulate cellular self-organization in a 2-dimensional cellular automata model, 3 phenomena could be realized: (1) an inner reaction system developed as an information carrier precursor (akin to DNA); (2) a cell border emerged (akin to a cell membrane); and (3) these cell structures could divide into 2. This double-structured cell was considered to be a primary biological cell. The outer loop evolved toward a lipid bilayer membrane, and inner polymeric particles evolved toward precursor information carriers (evolved toward DNA). This model did not completely clarify all the necessary and sufficient conditions for biological cell self-organization. Further, our virtual cells remained unstable and fragile. However, the “garbage bag model” of Dyson proposed that the first living cells were deficient; thus, it would be reasonable that the earliest cells were more unstable and fragile than the simplest current unicellular organisms.
TL;DR: The first systematic survey of the philosophical aspects and conundrums in the study of cosmic life can be found in this paper, where Ćirković presents a philosophical exploration of perplexing issues arising from contemporary research on the origin, existence and future of life in its widest cosmological context.
Abstract: Astrobiologists wrestle daily with the unwieldy question: Are we alone? If you are interested, read this authoritative book and give yourself an inspirational voyage to the habitable islands of the multiverse. Ćirković’s book is not an astrobiology textbook with facts and worked examples, but it is probably the best book on the philosophical implications of life in the universe, in the universe. This book describes itself as “the first systematic survey of the philosophical aspects and conundrums in the study of cosmic life.” and is “a philosophical exploration of perplexing issues arising from contemporary research on the origin, existence and future of life in its widest cosmological context.” (p4). These descriptions are accurate. The book is well-written, with long sentences that make sense, with commas, in the right, places. Like a good scientific result, this book raises and resusitates more questions than it answers – and in making these new questions more explicit, it offers us the most constructive gift that the philosophy of cosmology and biology can give to astrobiology. Instead of the chemical details of “Why Nature Chose Phosphates” (Westheimer 1987), Ćirković challenges himself and the astrobiological community to investigate what it is about our universe that makes observers possible. Milan Ćirković is a well-read polymath, science fiction enthusiast, Leonard Cohen fan and Serbian astronomer/historian/philosopher at the Astronomical Observatory of Belgrade. He has been prolific on selection effects in cosmology, multiverses, the history of human conceptions of extraterrestrials, SETI, and existential threats to humanity (e.g. Bostrom and Ćirković 2008). Like all of Ćirković’s work, this book is an insightful, authoritative window into the professional literature, where “professional literature” includes history, cosmology, philosophy, physics, evolutionary biology, SETI and the best science fiction. Unlike most astrobiologists, he is as informed about the history of the subject as he is about its current state. In this way he reminds me of Steven J. Gould and Antonio Lazcano. He gives us a tour de Orig Life Evol Biosph (2014) 44:159–163 DOI 10.1007/s11084-014-9369-2