Showing papers in "Origins of Life and Evolution of Biospheres in 1982"
TL;DR: Research concerning the possible role of clay in chemical evolution is reviewed and the probable importance of clays in the origin of life is assessed.
Abstract: Research concerning the possible role of clay in chemical evolution is reviewed. The probable importance of clays in the origin of life is assessed.
140 citations
TL;DR: Photochemical considerations suggest that a CH4−NH3 dominated early atmosphere was probably very short-lived, if it ever existed at all, and an early atmosphere of carbon dioxide (CO2) and nitrogen (N2) is favored by photochemical as well as geological and geochemical considerations.
Abstract: In the past, it was generally assumed that the early atmosphere of the earth contained appreciable quantities of methane (CH4) and ammonia (NH3). This was the type of atmosphere believed to be the most suitable environment for chemical evolution, the nonbiological formation of complex organic molecules, the precursors of living systems. Photochemical considerations suggest that a CH4-NH3 dominated early atmosphere was probably very short-lived, if it ever existed at all. Instead, an early atmosphere of carbon dioxide (CO2) and nitrogen (N2) is favored by photochemical as well as geological and geochemical considerations. Photochemical calculations also indicate that the total oxygen column density of the prebiological paleoatmosphere did not exceed 10 to the -7th of the present atmospheric level.
74 citations
TL;DR: In this paper, the influence of the composition of the mixture on the nature and amount of synthesized compounds on the organic chemistry at the periphery of Titan has been discussed, and the implications of the obtained results on Titan's organic chemistry are discussed.
Abstract: Numerous experiments have already been performed, simulating the evolution of gaseous mixtures containing CH4 when submitted to energy flux. From their results, it appears that a variety of organic compounds, including unsaturated hydrocarbons and nitriles such as HCN, can be synthesized into noticeable amounts from CH4-N2 mixtures. In particular, systematic studies of the influence of the composition of the mixture on the nature and amount of synthesized compounds show that organic volatile nitriles, and particularly cyanoacetylene and cyanogen, are formed only in media rich in nitrogen. Those nitriles have been identified very recently in the atmosphere of Titan, and thus, data from such laboratory experiments may provide important indirect information on the organic chemistry occurring at the periphery of this satellite of Saturn. However, during these experiments, there is a continuous formation and accumulation of molecular hydrogen, which does not occur in the atmosphere of Titan, because of H2 escape. In order to reassess the data already available from this type of laboratory studies, experiments on CH4-N2 atmospheres, with and without H2 escape, have been recently performed. The influence of this parameter on the chemical evolution of the atmosphere and on the nature and relative quantities of organic compounds has been studied. After reviewing these experiments, implications of the obtained results on the organic chemistry at the periphery of Titan are discussed.
57 citations
TL;DR: Conclusions reached from mechanistic studies are that the phosphorylations are a series of equilibrium reactions, with cyclic nucleotides being formed irreversibly.
Abstract: Nucleosides or deoxynucleosides were converted to a number of phosphorylated nucleotide and deoxynucleotide derivatives by ammonium or alkali dihydrogen phosphates in formamide. Conversions were smaller and slower at room temperature and greater and faster at elevated temperatures. Nucleotides afforded product mixtures similar to those obtained for nucleosides under the same conditions, indicating the occurrence of transphosphorylation processes. Products of reaction at elevated temperatures were cyclic nucleotides, nucleoside monophosphates, nucleoside diphosphates and cyclic nucleotide phosphates. The relative amounts of products formed were quite temperature dependent. Cyclic nucleotides were found to be in greatest abudance for reactions run at 125° or above. Relative yields of 2′, 3′ and 5′ nucleotides and 3′ and 5′ deoxynucleotides from several experiments are reported. 5′-Monophosphates were generally found to be present in larger quantities than 2′ or 3′ monophosphates. 2′-Deoxyadenosine showed a preference for phosphorylation at the 3′ position. Conclusions reached from mechanistic studies are that the phosphorylations are a series of equilibrium reactions, with cyclic nucleotides being formed irreversibly.
53 citations
TL;DR: Data are presented which establish that the observed uracil is not formed by decarboxylation of previously formed orotic acid, butvia acid hydrolysis of at least two other precursors, and is the first report of Uracil itselfvia HCN oligomerization.
Abstract: Uracil is released from HCN oligomers upon acid hydrolysis in concentrations of 0.001% for 1 M HCN solutions to 0.005% for 0.1 M solutions. This yield is comparable with earlier reported, minor or nonbiological pyrimidines such as 5-hydroxyuracil and orotic acid. This is the first report of uracil itself via HCN oligomerization. Data are presented which establish that the observed uracil is not formed by decarboxylation of previously formed orotic acid, but via acid hydrolysis of at least two other precursors.
53 citations
TL;DR: The carbon isotopic composition of modern marine algae and algal mats is more depleted in 13C than what would be expected from the carbon isotope composition of today's marine algae.
Abstract: Precambrian reduced carbon is more depleted in13C than what would be expected from the carbon isotopic composition of modern marine algae and algal mats. Since the photosynthetic carbon fixation by algae is the most likely source of the reduced carbon, the depletion has been considered an anomaly.
46 citations
TL;DR: A model is presented for the emergence of a primitive genetic code through the selection of a family of proteins capable of executing the code and catalyzing their own formation from polynucleotide templates, allowing an initially ambiguous system of catalysts to evolve to a coded, self-reproductive system.
Abstract: A model is presented for the emergence of a primitive genetic code through the selection of a family of proteins capable of executing the code and catalyzing their own formation from polynucleotide templates These proteins are assignment catalysts capable of modulating the rate of incorporation of different amino acids at the position of different codons The starting point of the model is a polynucleotide based polypeptide construction process which maintains colinearity between template and product, but may not maintain a coded relationship between amino acids and codons Among the primitive proteins made are assumed to be assignment catalysts characterized by structural and functional parameters which are used to formulate the production kinetics of these catalysts from available templates Application of the model to the simple case of two letter codon and amino acid alphabets has been analyzed in detail As the structural, functional, and kinetic parameters are varied, the dynamics undergoes many bifurcations, allowing an initially ambiguous system of catalysts to evolve to a coded, self-reproductive system The proposed selective pressure of this evolution is the efficiency of utilization of monomers and energy The model also simulates the qualitative features of suppression, in which a deleterious mutation is partly corrected by the introduction of translational error
32 citations
TL;DR: The formation of cyanate, which is one of the possible primitive condensing agents, was demonstrated by the detection of [Cu(Py)2] (NCO)2 that was formed by the addition of copper sulfate-pyridine reagent to the solution.
Abstract: A mixed gas of nitrogen, carbon dioxide, and hydrogen was discharged over 100 ml of 0.2 M NaHCO3 solution in a 5 liter discharge apparatus which simulates the primitive Earth. The formation of cyanate, which is one of the possible primitive condensing agents, was demonstrated by the detection of [Cu(Py)2] (NCO)2 that was formed by the addition of copper sulfate-pyridine reagent to the solution. In a series of experiments the partial pressures of nitrogen and carbon dioxide in the starting gas were fixed at 10 cm Hg and 20 cm Hg, respectively, whereas that of hydrogen was varied between 5, 10, 15, 20, 25, and 30 cm Hg. The discharges were continued for one week. The rate of appearance of cyanate was strongly dependent upon the partial pressure of hydrogen. The maximum rate of the production of cyanate at the initial stage of the discharge was in the case of 10 cm Hg of hydrogen, in which condition the starting gas is in a predominantly oxidized state. In this case the concentration of cyanate reached about 0.012 M after one day. Another discharge experiment was carried out with 0.2 M phosphate solution, and the production of carbamyl phosphate was demonstrated through the formation of ATP by the incubation of the discharged solution with ADP and carbamyl phosphokinase.
24 citations
TL;DR: Energy from ultraviolet and X-ray radiation environment of the primitive Earth is found to be much higher than previously believed and the influence of high energy radiation on the early development of life should be reexamined.
Abstract: Recent satellite observations of young, sun-like stars allow an estimation of the ultraviolet and X-ray radiation environment of the primitive Earth. Energy from these sources is found to be much higher than previously believed. We suggest that the influence of high energy radiation on the early development of life be reexamined.
18 citations
TL;DR: Information for tracing evolution even further could stem from the analysis of coenzyme mechanisms, as placing cofactors in their proper evolutionary context gives new hints concerning their actual mechanisms of catalysis.
Abstract: The evolutionary information obtained from sequencing proteins and RNA's fades out completely for early periods in evolution. Information for tracing evolution even further could stem from the analysis of coenzyme mechanisms. Likewise, placing cofactors in their proper evolutionary context gives new hints concerning their actual mechanisms of catalysis.
18 citations
TL;DR: A composite phylogenetic tree depicting an overview of prokaryote evolution based on the sequences of bacterial ferredoxin, 2Fe−2S ferred toxin, 5S ribosomal RNA, andc-type cytochromes shows three zones of major metabolic innovation in the Precambrian.
Abstract: A combination of the information on the metabolic capabilities of prokaryotes with a composite phylogenetic tree depicting an overview of prokaryote evolution based on the sequences of bacterial ferredoxin, 2Fe−2S ferredoxin, 5S ribosomal RNA, andc-type cytochromes shows three zones of major metabolic innovation in the Precambrian. The middle of these, which reflects the genesis of oxygenreleasing photosynthesis and aerobic respiration, links metabolic innovations of the anaerobic stem on the one hand and, on the other, proliferation of aerobic bacteria and the symbiotic associations leading to the eukaryotes. We consider especially those pathways where information on the structure of the enzymes is known.Halobacterium andThermoplasma (archaebacteria) do not belong to a totally independent line on the basis of the composite tree but branch from the eukaryote cytoplasmic line.
TL;DR: The chemistry and evolution of Titan's atmosphere were reviewed in light of the scientific findings from the Voyager mission as mentioned in this paper, and it was argued that the present N2 atmosphere may be Titan's initial atmosphere, rather than one photochemically derived from an original NH3 atmosphere.
Abstract: The chemistry and evolution of Titan's atmosphere are reviewed, in light of the scientific findings from the Voyager mission. It is argued that the present N2 atmosphere may be Titan's initial atmosphere, rather than one photochemically derived from an original NH3 atmosphere. The escape rate of hydrogen from Titan is controlled by photochemical production from hydrocarbons. CH4 is irreversibly converted to less hydrogen-rich hydrocarbons, which over geologic time accumulate on the surface to a layer thickness of about 0.5 km. Magnetospheric electrons interacting with Titan's exosphere may dissociate enough N2 into hot, escaping N atoms to remove about 0.2 of Titan's present atmosphere over geologic time. The energy dissipation of magnetospheric electrons exceeds solar EUV energy deposition in Titan's atmosphere by an order of magnitude, and is the principal driver of nitrogen photochemistry. The environmental conditions in Titan's upper atmosphere are favorable to building up complex molecules, particularly in the north polar cap region.
TL;DR: In this paper, aqueous solutions of adenosine and phosphorus pentoxide were incubated at 37°C for 5 months and HPLC analysis showed the formation of 2′-AMP, 3′AMP, 5′AMP and cyclic (3′-5′)-AMP.
Abstract: Possible formation of a P4O10 molecule in magma, the stability of the molecule in hydrous volcanic gas at high temperatures and a possible prebiotic phosphate cycle were discussed in relation to chemical evolution. To demonstrate the utility of phosphorus pentoxide as a phosphorylating agent, aqueous solutions of adenosine (0.02M) and phosphorus pentoxide (0.2M) were incubated at 37°C for 5 months. The pH of the solutions was adjusted every day or every few days to each fixed value (9.0, 10.5, 11.5, 12.5) with 10 N NaOH. The HPLC analysis showed the formation of 2′-AMP, 3′-AMP, 5′-AMP, cyclic (2′–3′)-AMP and cyclic (3′–5′)-AMP. The main components of the products were 2′- and 3′-AMP, though cyclic (2′–3′)-AMP was the main component in the early period of the incubation at pH 9.0. The yields (conversion rate of adenosine to AMPs) were increased almost linearly with the incubation time for 5 months in the case of pH 9.0. The final yields were about 3% (pH 9.0), 6% (pH 9.0, 1 M NaCl), 5% (pH 9.0, 0.01 M CaCl2, 0.01 M MgCl2), 7% (pH 9.0, 0.5 M NaCl, 0.01 M CaCl2, 0.01 M MgCl2), 9% (pH 9.0, 1 M NaCl, 0.01 M CaCl2, 0.01 M MgCl2), 32% (pH 10.5), 43% (pH 11.5), 35% (pH 12.5).
TL;DR: Any detection of HCN chemistry by the Voyager missions or the pending Galileo probe would constitute evidence for the hypothesis that heteropolypeptides on the primitive Earth were synthesized directly from hydrogen cyanide and water without the intervening formation of α-amino acids.
Abstract: Since hydrogen cyanide is a component of Titan's hazy atmosphere, HCN polymers might also be present by way of a low energy pathway leading initially to the synthesis of polyaminomalonitrile. Subsequent reactions of HCN with the activated nitrile groups of this HCN homopolymer would then yield heteropolyamidines, readily converted to heteropolypeptides following contact with frozen water on the surface of Titan. Similar HCN polymers in the reducing atmospheres of Jupiter and Saturn could be major contributors to the yellow-brown-orange appearance of these giant planets. Any detection of such HCN chemistry by the Voyager missions or the pending Galileo probe would constitute evidence for the hypothesis that heteropolypeptides on the primitive Earth were synthesized directly from hydrogen cyanide and water without the intervening formation of α-amino acids.
TL;DR: D- and L-Leucine have been subjected to 39–55 percent radiolysis using 0–11 MeV protons, both with the proton beam passing through the sample or being absorbed by it, and with quenching the sample immediately on completion of irradiation or after a 21-day interval.
Abstract: D- and L-Leucine have been subjected to 39-55 percent radiolysis using 0-11 MeV protons, both with the proton beam passing through the sample or being absorbed by it, and with quenching the sample immediately on completion of irradiation or after a 21-day interval. Racemization was small (1.1-1.7 percent) and comparable in all cases, suggesting that radioracemization and secondary degradative effects were not important factors in our recent unsuccessful attempts to induce optical activity in DL-leucine by partial radiolysis using 0-11 MeV longitudinally polarized protons.
TL;DR: In this article, the selection effect of external asymmetric agents in the process of generation and amplification of biomolecular asymmetry is studied, and it is pointed out that this effect will play an important role at bifurcation point, but when the asymmetry has been amplified to a certain extent, a weak asymmetric agent will no longer be able to change the chirality of the system.
Abstract: A simple criterion for mirror symmetry breaking in a non-linear chemical system is presented. The selection effect of external asymmetric agents in the process of generation and amplification of biomolecular asymmetry is studied. It is pointed out that this effect will play an important role at bifurcation point, but when the asymmetry of a system has been amplified to a certain extent, a weak asymmetric agent will no longer be able to change the chirality of the system.
TL;DR: There are at least some twentyfive specific conditions or requirements which have to be fulfilled in order for life as the authors know it to appear and evolve in a planetary system such as theirs, and in order to extend this inquiry to other systems beyond their solar system a fifth set of requirements based on astronomical observations are discussed.
Abstract: During the past years we have explored most of the bodies of the solar system by means of the Apollo, Venera, Viking, Voyager, and other space missions. We are now in a better position to be able to compare the conditions of other planets and satellites with those of the Earth in order to determine what is unique about our planet which permitted the emergence and evolution of life on it. On the basis of this and other available scientific information we have arrived at the conclusion that there are at least some twentyfive specific conditions or requirements which have to be fulfilled in order for life as we know it to appear and evolve in a planetary system such as ours. Most of these necessary conditions or requirements are mutually interdependent, but in order to discuss their role in depth they have been divided into five major general areas which are discussed in some detail herein.
TL;DR: The spectral reflectivity of the Titan tholins has been measured between 0.38 and 1.1/am, and in this wavelength range follows, within the probable errors, the measured reflectance of Titan.
Abstract: In the light of Voyager 1 Titan results, a mixture of 9 % CH4 and 91% N2 was exposed for 107 s at a total pressure of 73 mb to high frequency electrical discharge. The gas phase products include NHa, HCN, (CN)2 and other molecules. Solid phase products, here called tholins, appear as a thin red film which, under scanning electron microscopy, is found to be comprised of irregular micron and sub-micron sized particles, with a preponderance of particles exhibiting a radius ~0.3/~m. The wavelength-dependent real part of their refractive indices n ~ 1.6 + 0.1. These properties seem to be consistent with those deduced for the Titan aerosols from Earth-based observations (Rages and Pollack, Icarus 41, 119, 1980). Values of n(X) and k(X), and the UV, visible and IR reflectivities of these tholins have been measured, and compared with the CH4/NH3 and CH4/NH3/H2S tholins described earlier (Khare et aL, Science 199, 1199, 1978; Sagan and Khare, Nature 277, 102; 292, 536, 1979). The spectral reflectivity of this tholin has been measured between 0.38 and 1.1/am. The tholin absorbs strongly between 0.38 and 0.60/am, and in this wavelength range follows, within the probable errors, the measured reflectance of Titan. At longer wavelengths, where the CH4 Kuiper bands become prominent, the tholin, not masked by CH4 absorption, continues to increase in reflectivity. We find that the infrared absorption spectra or tholins we have previously reported on can be explained by a weighted linear superposition of the absorptions by the most abundant organic functional groups appearing as GC/MS pyrolyzates. The infrared spectrum of the Titan tholin is similar, and suggests that this material is a complex heteropolymer which contains, among others, nitrile and hydrocarbon functional groups. The infrared reflection spectra of the Titan tholin longward of 6 lain and in the near ultraviolet are flat and approximately featureless, consistent with Titan observational results from the International Ultraviolet Explorer and from the Voyager IRIS experiments, respectively. The Titan tholin may include polynitriles with hydrocarbon functional groups. It seems likely that the Titan clouds are composed, at least in part, of organic molecules, as proposed some years ago (Sagan, Space Sei. Revs. 11, 73, 1971; Icarus 18, 649, 1973; Khare and Sagan, Icarus 20, 311, 1973). From the direct photolysis of methane alone by ultraviolet light at wavelengths shortward of 1440 A, the accumulation of organic tholins on the surface of Titan over geological time amounts to a surface layer tens of meters thick. Other energy sources serve to increase this number. At the 95 K surface temperature of Titan these organic heteropolymers will tend to be preserved for very long periods of time. It is therefore possible that the surface of Tian is a planet-scale repository of some of the early steps which led on Earth more than 4 x 109 yrs ago and in the presence of liquid water to the origin of life. It is also conceivable that the abundant water ice in the interior of Tian (deduced from the satellite's bulk density) is intermittently released in liquid form to the surface, and that subsequent aqueous tholin chemistry occurs, even if episodically and on local scales.
TL;DR: NH3 photolysis in the H2-abundant atmosphere of Jupiter is not responsible for the presence of the carbon compounds observed there such as ethane, acetylene, and hydrogen cyanide, but may have had a role in the early atmosphere of Titan.
Abstract: Photolysis of NH3 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed (delta CH4/delta NH3). The loss arises from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms, the presence of which is established by the constancy of delta CH4/delta NH3 between 298 and 156 K and by the quenching of the abstraction reaction when either H2 or SF6 is added. From the latter result, it can be concluded that NH3 photolysis in the H2-abundant atmosphere of Jupiter is not responsible for the presence of the carbon compounds observed there such as ethane, acetylene, and hydrogen cyanide, but may have had a role in the early atmosphere of Titan. Photolysis of PH3 with a 206 nm light source gives P2H4, which in turn is converted to a red-brown solid (P4?). The course of the photolysis is not changed appreciably when the temperatures is lowered to 157 K except that the concentration of P2H4 increases. The presence of H2 has no effect on the P2H4 yield. Photolysis of 9:1 NH3:PH3 gives a rate of decomposition of PH3 that is comparable with that observed by the direct photolysis of PH3. Comparable amounts of P2H4 and the red-brown solid are also observed. The mechanisms of these photochemical reactions together with their implications to the atmospheric chemistry of Jupiter are discussed. The structures of the compounds responsible for the wide array of colors e.g., brown, red and white, observed in the atmosphere of Jupiter have been the subject of extensive speculation. One theory suggests that these colors are due to organic materials formed by the action of either solar ultraviolet light or electric discharges on mixtures of CH4, NH3 and NH4HS in the Jovian atmosphere (Ponnamperuma, 1976; Khare et al., 1978). An alternative hypothesis is that the colors are due to inorganic compounds resulting from the photolysis of NH4HS and PH3 (Lewis and Prinn, 1970; Prinn and Lewis, 1975). In this paper we will summarize our experiments which were designed to test some of these hypotheses.
TL;DR: A new model of the code and translation is developed in which the pairs AU and GC play complementary roles, and in which tRNAs develop from a molecule with two loops which stacks in repetitive patterns without the need for a messenger RNA.
Abstract: Several models have been advanced, both in this journal and others, for the development of the genetic code and translation apparatus. Eigen in particular has put forward a detailed model based on the hypercycle. This paper uses some of these previous ideas to develop a new model of the code and translation in which the pairs AU and GC play complementary roles, and in whichtRNAs develop from a molecule withtwo loops which stacks in repetitive patterns without the need for a messenger RNA. Thus a bridge is provided between random, (or autocatalytic) polymerization, and coded translation. In addition, alternative postulates to several of Eigen's ideas are tested by computer simulation.
TL;DR: The primitive replication-coupled system would then have been able to synthesize specific proteins containing one amino acid residue for each primitive tRNA incorporated during replication, giving rise directly to triplet-coded protein synthesis.
Abstract: A mechanism is suggested for the replication under primitive conditions of long polynucleotides by the sequential incorporation of sequences related to those of modern transfer RNAs. It is proposed that replication of such molecules became established as the result of a replicative advantage arising from the concomitant linkage together of amino acids to form polypeptides. Initially these polypeptides may have been of random sequence. Selection of primitive tRNAs in which the amino acid and anticodon stem sequences were rotaionally symmetrical could have led to specific, anticodon-directed aminoacylation and fixation of the genetic code along the lines suggested by Hopfield. (Hopfield, 1978). The primitive replication-coupled system would then have been able to synthesize specific proteins containing one amino acid residue for each primitive tRNA incorporated during replication. The end result of this line of evolution is postulated to have been a nucleoprotein structure resembling the ribosome. The primitive system would then have been able to give rise directly to triplet-coded protein synthesis. Some recent RNA sequence data are discussed which are consistent with derivation of modern protein synthesis from the primitive replication-coupled mechanism.
TL;DR: High molecular weight soluble polymers (HMWSP) were separated from low molecular weight ones by dialysis and it was shown that these polymers catalyzed the dehydrogenation of NADH and reduction of resazurin.
Abstract: Eighteen protein amino acids with milk casein composition were heated in a modified sea medium. Marigranules were formed in the precipitates and soluble polymers were formed in the supernatant. Time course of the reaction (ultraviolet spectra, the concentration of metal ions, and the concentration of amino acids in the supernatant) were measured. The time course of the formation of the soluble polymers was also studied by Bio-Gel P-2 column. High molecular weight soluble polymers (HMWSP) were separated from low molecular weight ones by dialysis. It was shown that these polymers catalyzed the dehydrogenation of NADH. These polymers also catalyzed the coupled reaction between dehydrogenation of NADH and reduction of resazurin. This coupled reaction was accelerated by the light.
TL;DR: Succinic acid is converted into other carboxylic acids by ionizing radiation and its role in biological systems may be related to its prebiotic occurrence.
Abstract: Succinic acid is converted into other carboxylic acids by ionizing radiation. The results obtained have been correlated with the ready formation of this compound in prebiotic experiments. Its role in biological systems may be related to its prebiotic occurrence.
TL;DR: In this article, experiments were conducted to simulate the atmospheric chemistry of Titan using a mixture of N2 and CH4, which was comparable to ratios determinded by Voyager data, and the resulting products were analyzed.
Abstract: Experiments were conducted to simulate the atmospheric chemistry of Titan. Gaseous mixture of N2 and CH4 was utilized which was comparable to ratios determinded by Voyager data. Ultraviolet radiation, electric discharge, ),-radiation, and electron and proton impact were employed, and the resulting products analyzed. The UV simulations produced saturated hydrocarbons. No unsaturated compounds or nitrogen-containing compounds were observed. The electric discharge and the ionizing and particle radiation experiments produced HCN and unsaturated hydrocarbons. These findings agree with the data received from the IRIS experiment.
TL;DR: Examination of the stability of amino acids in chert under dry-heating conditions suggests that these amino acids have been preserved with a predominance of L-enantiomers in the Precambrian chert, indicating that the amino acids isolated from the Thule samples were chemical fossils and not recent contaminants.
Abstract: Amino acids were recovered at a concentration level of 10−9 M/g from the interior of chert and dolomite of the Late Precambrian Thule Group. Examination of the stability of amino acids in chert under dry-heating conditions suggests that these amino acids have been preserved with a predominance of L-enantiomers in the Precambrian chert. Enantiomer analysis of amino acids in dolomite showed a thermal effect resulting from a late Precambrian igneous intrusion. This evidence indicates that the amino acids isolated from the Thule samples were chemical fossils and not recent contaminants.
TL;DR: Results may suggest that poly(A) containing messenger arised at very early stage of evolution prior to the divergence between archaebacteria and eukaryotes.
Abstract: An acido-thermophillic archaebacteria,Thermoplasma strain KO-2, produced poly(A) containing RNA. The isolated poly(A)RNA showed the messenger activity in a cell-free extract of rabbit reticulocyte, indicating that the RNA is mRNA of the archaebacteria. 7-Methylgluanosine 5′-phosphate did not inhibit the reaction, suggesting that the cap structure is not present in the messenger. These results may suggest that poly(A) containing messenger arised at very early stage of evolution prior to the divergence between archaebacteria and eukaryotes.
TL;DR: This biogeochemical viewpoint leads to a quantitative analysis of life activity and is applied to analyses of possible early developments of life and of an impact of present human activity on the global carbon cycle.
Abstract: Intertwined cycles of matters are proposed to be one of the essential characteristics of life. The increase in the amount of recycled matters within biological groups and the complication of the cycling network are considered to be the early development of life soon after its appearance on the Earth. From this point of view, the origin of a cell alone can not sufficiently be regarded as the origin of life. The origin of a cell must be followed by a formation of material cycling among cells, if the cells are to stay on the Earth long enough so that they could be called life. This biogeochemical viewpoint leads to a quantitative analysis of life activity. A formula is presented to exemplify the potential utility of the viewpoint. It is applied to analyses of possible early developments of life and of an impact of present human activity on the global carbon cycle. Further application of the viewpoint to a variety of biogeochemical, sociogeochemical, ecological, and environmental problems should eventually show whether there is some utility in this view.
TL;DR: In this paper, the coacervate droplets were made from PVA-A and PVAS and they were irradiated by UV light, which protected them from the photochemical decomposition.
Abstract: Functions of coacervate droplets as protocells are studied by using synthetic polymers. The coacervate droplets were made from PVA-A and PVA-S. When glycine or diglycine were in the surrounding medium, the coacervate droplets concentrated them. The concentration of glycine in the coacervate droplets was higher than that of diglycine. When this mixture was irradiated by UV light, the coacervate droplets protected them from the photochemical decomposition.
TL;DR: The idea that ambiguity would allow the length of the codon to change is very useful, since it predicts the distribution of the 4-blocs and 2- Blocs in the code, determines where variations in the codes are probable, and presents a scenario for the evolution of the code.
Abstract: The evolution of the genetic code is an extremely complex problem. The addition of a new method by which the code could evolve, however, allows much to be explained about the way in which the present codes (Γ3 and Γ
3
⋆
) originated. The idea that ambiguity would allow the length of the codon to change is very useful, since it predicts the distribution of the 4-blocs and 2-blocs in the code, determines where variations in the code are probable, and presents a scenario for the evolution of the code.