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Electrochemical oxidation at room temperature of a slurry of Ag2Cu2O3 yields a new silver copper oxide, formulated as Ag2Cu2O4, with one more atom of oxygen per unit formula, that can in turn revert to the original precursor. The resulting oxide presents a different electronic and crystal structure from its precursor, as shown by XPS, X-ray and electron diffraction. This phase transformation involves a radical structural change from a 3D to a 2D network, as well as electronic changes involving silver and oxygen. The potential of electrochemical techniques to induce crystal-chemical solid state transformations is analyzed., The authors thank J.P. Espinós, Fundación Domingo Martínez and the MCYT grants (PB98-0491 and MAT2002-04529-C03).

The hypothesis that vestiges of the ancestral RNA-dependent RNA polymerase involved in the replication of RNA genomes of Archean cells are present in the eubacterial RNA-polymerase beta-prime subunit and its homologues is discussed. It is shown that, in the DNA-dependent RNA polymerases from three cellular lineages, a very conserved sequence of eight amino acids, also found in a small RNA-binding site previously described for the E. coli polynucleotide phosphorylase and the S1 ribosomal protein, is present. The optimal conditions for the replicase activity of the avian-myeloblastosis-virus reverse transcriptase are presented. The evolutionary significance of the in vitro modifications of substrate and template specificities of RNA polymerases and reverse transcriptases is discussed.

More than thirty polycyclic aromatic hydrocarbons, including nine heterocyclic aromatic compounds, have been identified in solvent extracts of the Murchison meteorite by gas chromatography-mass spectrometry using bonded-phase fused silica columns. Structural isomers of several alkylated aromatic hydrocarbons, including methylpyrene and methylphenanthrene were chromatographically separated, thus allowing calculations of the amount of alkyl substituted compounds in the solvent extracts. The ratio of odd-carbon number to even-carbon number was found to be approximately 0.1. Based on these data and literature data from model pyrolysis experiments, a temperature of 1000°C is suggested for the formation of polycyclic aromatic hydrocarbons in the solar nebula or premeteoritic body. The value of 1000°C is within the range of temperatures for the condensation of the nebular material from the initial high temperature phases to the lower temperature phases at which chemical and isotopic equilibria were frozen. A simple model for the abiotic synthesis of heterocyclic compounds from simple aliphatic precursors is also presented.

Experiments were performed in which meteoritic iron, iron ore and nickel-iron alloy were used to catalyze (in Fischer-Tropsch synthesis) the reaction of deuterium and carbon monoxide in a closed vessel. Normal alkanes and alkenes and their monomethyl substituted isomers and aromatic hydrocarbons were synthesized. Iron oxide and oxidized-reduced Canyon Diablo used as Fischer-Tropsch catalysts were found to produce aromatic hydrocarbons in distributions having many of the features of those observed in carbonaceous chondrites, but only at temperatures and reaction times well above 300 C and 6-8 h.

The neutral lipids of nine methanogenic and three thermoacidophilic bacteria were analyzed. The major compounds are acyclic isoprenoids in the range of C15 to C30. The compounds were identified by means of their mass spectral fragmentation pattern and/or by co-chromatography. A high similarity is seen between the isoprenoid content of the examined bacteria and the distribution of these compounds in ancient sediments and petroleum.

During the last three decades major advances have been made in our understanding of the formation of carbon compounds in the universe and of the occurence of processes of chemical evolution. 1) Carbon and other biogenic elements (C,H,N,O,S and P) are some of the most abundant in the universe. 2) The interstellar medium has been found to contain a diversity of molecules of these elements. 3) Some of these molecules have also been found in comets which are considered the most primordial bodies of the solar system. 4) The atmospheres of the outer planets and their satellites, for example, Titan, are actively involved in the formation of organic compounds which are the precursors of biochemical molecules. 5) Some of these biochemical molecules, such as amino acids, purines and pyrimidines, have been found in carbonaceous chondrites. 6) Laboratory experiments have shown that most of the monomers and oligomers necessary for life can be synthesized under hypothesized but plausible primitive Earth conditions from compounds found in the above cosmic bodies. 7) It appears that the primitive Earth had the necessary and sufficient conditions to allow the chemical synthesis of biomacromolecules and to permit the processes required for the emergence of life on our planet. 8) It is unlikely that the emergence of life occurred in any other body of the solar system, although the examination of the Jovian satellite Europa may provide important clues about the constraints of this evolutionary process. Some of the fundamental principles of chemical evolution are briefly discussed.

The cell size and DNA and protein content of bacteroids fractionated from alfalfa and soybean nodules by buoyant density sedimentation were examined by laser flow-microfluorometry. In alfalfa nodules, these parameters were inversely related to bacteroid density. The bacteroids which sedimented at the highest density ( p = 1.268 ) resembled free-living Rhizobium meliloti in cell size and protein content but averaged slightly higher in DNA content. The bacteroids which sedimented at the lowest density ( p = 1.224 ) averaged larger in size and contained significantly more DNA and protein then free-living R. meliloti. Despite the difference in density, bacteroid fractions from soybean nodules and free-living Rhizobium japonicum were similar in all measured parameters.

An alkane distribution in which isoprenoid alkanes are present in excess of n -paraffins and pristane, phytane, and norpristane (in this order) are the major components, has been found in two different beds of the Irati oil shale, Brazilian Permian formation of Sao Mateus do Sul, Parana.

Deoxynucleoside 5'-monophosphates were condensed by cyanamide or by l-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of ammonium chloride at 0 degree, 37 degrees or 60 degrees C through several cycles of evaporation to dryness with replenishment of all reactants at each cycle. We found that at 37 degrees or 60 degrees cyanamide gives distinctly more high molecular weight material than does carbodiimide. Indeed, the yield of condensed products for the cyanamide reaction (dimers and higher oligomers) was found to be between 60 percent and 80 percent. The molecular weight distribution of the product shifts to higher molecular weights as cycling continues at 37 degrees or 60 degrees for both condensing agents. The water soluble carbodiimide gives higher yields of low molecular weight product but much lower yields of the higher molecular weight products. At 0 degree yields of high molecular weight product were low for both condensing agents. Results of characterization of the products demonstrate the synthesis of oligodeoxynucleotides including tetramers, with 3'-5' phosphodiester linkages.

The Precambrian is the longest and least understood period in the history of our planet. There is no direct evidence which bears on the primitive Earth environment, the synthesis of organic compounds and the origin of life on our planet, since the geological record only goes back to 3.8 Ga ago. To overcome this deficiency it is necessary to extrapolate backwards from 3.8 Ga ago to the time when the Earth was formed, ∼ 4.6 Ga ago, and also make use of additional scientific approaches. These include models of the solar nebula and planet formation, comparative observations with other cosmic environments, and experimental simulation studies under plausible primitive Earth conditions, particularly in regard to the prebiological synthesis of organic compounds. A large number of interstellar organic molecules have been detected by radioastronomy in the interstellar medium, particularly in places where other solar systems may be in the process of formation. It is remarkable that ∼ 10 of these molecules are known to be the precursors of the most important biochemical monomers. Furthermore, some of these monomers, e.g., amino acids, purines and pyrimidines, have also been detected in carbonaceous chondrites, which were presumably synthesized on the parent bodies of the meteorites or possibly in the solar nebula. Comparative studies on the terrestrial planets indicate that their primitive atmospheres resulted primarily from outgassing of CO2 and other partially oxidized (CO, N2) and reduced (H2, CH4, NH3, H2S) volatiles. Furthermore, comets and meteorites are thought to have made a significant contribution to the reduced carbon precursors for the prebiological synthesis of biochemical compounds. A brief review of the experiments carried out in the laboratory under possible primitive Earth conditions shows that amino acids, purines, pyrimidines, monosaccharides, fatty acids and other compounds are readily obtained using different energy sources. However, the formation of oligopeptides, oligonucleotides and phospholipids requires more restrictive conditions. They have been synthesized by means of condensing agents, such as cyanamide, as well as by heating under relatively dry conditions of less than 100°C. Experiments have been carried out on the formation of liposomes from prebiotically synthesized phospholipids. Also, using 2-methylimidazolide derivatives of nucleotides, the template directed synthesis of polynucleotides has been demonstrated. In the latter experiments a high fidelity of complementary base pairing has been observed, which if further improved would approach that of enzyme catalyzed replication. However, it is not known how the prebiologically synthesized polymers became organized into a self-replicating system. At any rate the first living systems were probably very rudimentary heterotrophic micro-organisms which used organic compounds from the environment for both cell components and energy. They were probably followed by fermenters and eventually by autotrophic CO2 reducing micro-organisms similar to the methanogenic and photosynthetic bacteria.

The influence of ammonia on the pyrolysis pattern of selected organic substances sorbed on an inorganic phase was investigated. The thermal degradation products were identified by gas chromatography-mass spectrometry. The feasibility of this technique was tested on a meteoritic sample. All substances examined react with ammonia at the pyrolysis temperature of 500 C, the major products being nitriles and heterocyclic compounds in which nitrogen was incorporated. Based on these results, a model for the non-equilibrium production of organic compounds on Jupiter is discussed. The investigation was performed in connection with the Viking lander molecular analysis. The results obtained indicate that the concentrations of ammonia in the retrorocket fuel exhaust would have been probably too small to produce significant changes in the Martian soil organic compounds if any were found.

A comparative study of the stable carbon isotopes, the aliphatic and aromatic hydrocarbons and the normal fatty acids in four differentiated organic phases (designated in this report as bitumens A, B, C and D) from Windy Knoll, Derbyshire, England, shows the following: 1. (1) The average abundances of 13C (relative to the P.D.B. standard and in parts per thousand) in the bitumens vary from −28.0 (bitumen B) to −30.7 (bitumen C) well within the range of petroleum. 2. (2) Isoprenoid hydrocarbons are present in bitumen A (C14 - C21; 198 p.p.m.), bitumen B (C15 - C20; 11 p.p.m.), bitumen C (C15 - C23; 157 p.p.m.) and bitumen D (C16, C18 - C23; 515 p.p.m.) 3. (3) Normal alkanes are present in bitumen A (

The extractable aliphatic hydrocarbons of several meteorite specimens (carbonaceous chondrites and graphite-troilite nodules of iron meteorites) as well as several terrestrial graphites were separated and identified by the combination of gas chromatography—mass spectrometry. Due to the extreme complexity of the hydrocarbons in these samples and the very low levels of concentration in which the individual components are present, unequivocal structural assignments can only be obtained by means of their respective mass spectral features. From the mass spectrometric patterns eleven homologous series of aliphatic hydrocarbons have been identified. These include the n-alkane series, two isoprenoid series of 2,6,10-trimethyl- and 2,6,10,14-tetramethyl-alkanes, five series of monomethyl substituted alkanes (2-, 3-, 4-, 5-, 6-methylalkanes), one of 4,8-dimethylalkanes, and two of monocycloalkanes (cyclohexyl and cyclopentyl). From the data obtained we can establish interesting correlations between the two types of samples, terrestrial and extraterrestrial, and also determine whether these compounds were derived from biological or abiological sources. The evidence points to possible terrestrial contamination of the meteoritic materials by contact with dust, air or petroleum fumes.

Iron meteorites graphite-troilite nodules isomeric alkane composition, using gas chromatography and mass spectrometry

The aliphatic hydrocarbons in two specimens of limestone (one from Texas and the other from Italy) which were weathered in place as parts of building structures have been investigated using gas chromatography and gas chromatography-mass spectrometry. The hydrocarbons in 1. (i) the limestone from Texas and 2. (ii) algae cultured from this limestone have similar distributions, i.e. the predominating hydrocarbon in both cases is n-C17, thus indicating that most of the aliphatic hydrocarbons in the limestone may be derived from recent algal growth. The hydrocarbons in the limestone from Italy, in which n-C17 is a maximum but which also include relatively large amounts of pristane, phytane and other aliphatic hydrocarbons, appear to be a mixture of in situ biogenically derived hydrocarbons and extraneously derived fossil hydrocarbons.

Fatty acids ranging from 14:0 to 18:4 were found in eleven different species of green and blue-green algae. In general, the unsaturated C18 fatty acids predominate in all the species of green algae analyzed while with some exceptions the C16 saturated acids are predominant in the blue-green algae. By the nature of their as chromatographic patterns, there appears to be no direct correlation between the fatty acids and the hydrocarbons within the same species of algae. The fatty acids are distributed in a narrower molecular weight range (C14C18) than the hydrocarbons (C15C33) and do not show any significant qualitative variations between species. All assignments of structural identities are supported by gas chromatographic and mass spectrometric data.

Aliphatic hydrocarbons ranging from C13 to C33 have been identified in dust. Isoprenoids and other isomeric alkanes have also been detected in some of the dust samples. The widespread occurrence of dust particles makes them a potential contaminant of extraterrestrial and geochemical specimens being analyzed for organic compounds.

In addition to adenine, the supernatant solution from the product of the base-catalyzed condensation of hydrogen cyanide in aqueous ammonia contains several purine precursors such as 4-aminoimidazole-5-carboxamide, 4-aminoimidazole-5-carboxamidine, formamide, and formamidine. It also contains glycinamide, glycine, alanine, aspartic acid, and a large number of unidentified ultraviolet-absorbing and fluorescing compounds. The data obtained indicate that the mechanism of adenine synthesis occurs by formation of a hydrogen cyanide trimer, possibly aminomalonodinitrile, which either directly or after transformation to its mono- or diamidine condenses with formamidine to form 4-aminoimidazole-5-carboxamidine. This imidazole derivative condenses in the final step with another molar equivalent of formamidine to form adenine. Less likely alternative mechanisms of adenine synthesis are also described. These results are considered to be of significance in relation to the formation of imidazoles and other heterocyclic compounds on the abiotic earth. The fact that not only adenine, but also amino acids and polypeptides can be synthesized under similar conditions to the ones used in these experiments supports strongly the geochemical models with reducing conditions proposed by Oparin, by Urey, and, more recently, by Oro for the formation of biochemical compounds on the primitive earth.

Gas chromatography and combined gas chromatography and mass spectrometry have been used to study the distribution of fatty acids and hydrocarbons in the seeds of Plantago ovata . The occurrence in the seed coat of the low molecular weight hydrocarbons (C 16 -C 19 ) with a significant percentage of an even carbon-numbered hydrocarbon (anteiso-C 18 ; 10·1 per cent) were unusual features in relation to earlier reports on plant hydrocarbons. The seed coat of P. ovata showed mainly linoleic, oleic, and palmitic acid in decreasing concentrations while the seed itself did not contain an appreciable amount of fatty acids. The results rule out a simple precursor-product relationship between fatty acids and hydrocarbons as the likely pathway to explain the biogenesis of all the hydrocarbons.

Carbonaceous chondrites isomeric alkanes identification by mass spectrometry and gas chromatography

The major components of the lipid fraction of the leaves of cabbage have been identified by means of gas Chromatography and combined gas chromatography-mass spectrometry. The saturated hydrocarbons ranged predominantly from C27 to C31 with C29 comprising the vast majority (92 per cent) of the n-heptane fraction examined. Mass spectra information is presented for the first time which provides confirming evidence for the structure of a symmetrical ketone containing 29 carbon atoms. A number of unsaturated and saturated fatty acids were also identified; the major components being linolenic, linoleic, and palmitic, which together constituted more than 50 per cent of the total fatty acids present.

Recent investigations have implicated a correlation between the hydrocarbon composition of algae and that found in geological sediments. This report presents information on hydrocarbon production by twelve species of algae, morphologically similar to fossil forms, including Anacystis cyanea, A. montana, Spirulina platensis, Lyngbya aestuarii, Chroococcus turgidus, Chlorella pyrenoidosa, Coelastrum microsporum, Tetraedron sp. and Scenedesmus quadricauda, along with confirmatory data on Anacystis nidulans, Nostoc sp. and Botryococcus braunii which have previously been reported. The normal hydrocarbon range is from C15 to C19 in most species, and n-C17 is predominant in all cultures. However, a few of the species show a bimodal distribution of aliphatic hydrocarbons with maxima at C17 and C27, with significant amounts of C23, C27, and C29 straight-chain olefins and paraffins. Similar bimodal distributions of saturated hydrocarbons have been observed in both tertiary and Precambrian sediments, supporting the interpretation of biological origin. The production of methyl-substituted alkanes by blue-green algae and a tentative identification of a triterpene from three species is also reported. Squalene is the only isoprenoid reported.

Adenine has been synthesized in substatial amounts by heating a solution of hydrogen cyanide (1 to 15 M) in aqueous ammonia for one or several days at moderate temperatures (27 ° to 100 °). The insoluble black polymer of hydrogen cyanide was removed by centrifugation and adenine was isolated from the red-brown supernatant by chromatographic methods. The main ultraviolet absorbing compound of the reaction product was identified as adenine by eight different procedures, among which, ultraviolet spectrophotometry, melting point of its picrate, and the specific method of Gerlach and Doring were used. From a 11.1 M hydrogen cyanide reaction mixture, at 70 °, a yield of 110 mg. of adenine per liter of original reaction mixture was obtained, which could be increased to 685 mg. by evaporation of the supernatant to dryness on the steam bath and subsequent treatment of the residue with hydrochloric acid. Since adenine is an essential building block of nucleic acids and of the most important coenzymes, and since hydrogen cyanide, ammonia and water are common natural constituents of the solar system, these experiments are considered of significance in relation to the problem of the origin of life. In particular, the experiments provide the first demonstration of the spontaneous synthesis of adenine from simple compounds of carbon and nitrogen under conditions presumed to have existed on the primitive earth.

Abiotic synthesis of meteoritic aliphatic hydrocarbons produced by open flow Fischer- Tropsch processes for hydrogen and Co interactions

Aromatic and nonaromatic hydrocarbon fractions in terrestrial graphite, discussing classification and analysis by chromatography and mass spectrometry

Polyglycines with average degrees of polymerization up to 18 were synthesized by heating glycine in aqueous ammonium hydroxide solutions. The rate of the reaction increased with the ammonium hydroxide concentration, and the optimum temperature of synthesis was found at about 140 °C. The polymers are white, light powders, soluble in lithium bromide solutions; they are biuret-positive and yield glycine upon acid hydrolysis. The infrared spectra in KBr disks has shown that the polymers have the configuration of polyglycine II. The significance of these findings in relation to the formation of polypeptides on the primitive earth according to the theory of Akabori is briefly discussed.