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The prebiotic synthesis of His and its dimer has led us to study the possible catalytic properties of His-His. The enhancing effect of His-His has been tested in the dephosphorylation of dAMP, the hydrolysis of oligo(A)12, and the oligomerization of 2'3'-cAMP.

The most frequently invoked explanation for the origin of metabolic pathways is the retrograde evolution hypothesis. In contrast, according to the so-called "patchwork" theory, metabolism evolved by the recruitment of relatively inefficient small enzymes of broad specificity that could react with a wide range of chemically related substrates. In this paper it is argued that both sequence comparisons and experimental results on enzyme substrate specificity support the patchwork assembly theory. The available evidence supports previous suggestions that gene duplication events followed by a gradual neoDarwinian accumulation of mutations and other minute genetic changes lead to the narrowing and modification of enzyme function in at least some primordial metabolic pathways.

The synthesis of putrescine was accomplished by decarboxylation of L-ornithine when this amino acid was heated in aqueous solution and in the absence of oxygen. Chromatographic, radioisotopic, and enzymatic techniques were used to demonstrate that one mole of non-radioactive putrescine and one mole of 14CO2 was formed during the heating of L-(l-14C)-ornithine. This work indicates that the synthesis of putrescine can occur starting with ornithine and in conditions that are presumed could have existed on the primitive Earth. The possible significance of these results in the prebiotic molecular evolution is briefly discussed.

According to Oparin, Mendeleev thought that the origin of petroleum was the result of the hydrolysis of iron carbides by superheated steam under pressure from the deep interior of the Earth through geological formations where the metal carbides exist. As early as 1877, Mendeleev described the reaction leading to the synthesis of hydrocarbons according to the general equation 3Fe(sub m)C(sub n) + mH2O yields mFe3O4 + C(sub 3n)H(sub 8m). Other experimental studies on the production of hydrocarbons from cast iron have been reported. Because of the possibility that hydrocarbons may have been trapped within the carbon matrix of the cast iron, which usually has a high content of carbon, we have studied the reaction of pure iron carbide with deuterium chloride and deuterated water. This was done in order to distinguish any newly formed deuterated hydrocarbons from any possible impurities of trapped hydrocarbons. The experiments were carried out by simply allowing iron carbide to react with concentrated deuterium chloride in D2O. The volatile hydrocarbon fraction examined by gas chromatography-mass spectrometry (GC/MS), using a Finnigan 1020/OWA instrument. contained low molecular weight hydrocarbons in a range C3 to C7. Lower molecular weight hydrocarbons were not detected by GC/MS because the MS scanning mode was preset above mass 40 to exclude components of air. The identified hydrocarbons are similar to those obtained under prebiotic conditions using high frequency discharge. The hydrocarbons found in common were propane, butane, pentane, 3-methylpentane, hexane, and heptane. The percent yields decline with increasing carbon number (propane 11%, n-heptane 1%). Similar results have been obtained by the direct treatment of metal carbides by pulse laser vaporization mass spectrometry. These results show that the hydrolysis of iron carbides may have been a significant source of hydrocarbons on the primitive Earth. There appears to be a predominance of straight chain isomers, which may have been important in the prebiotic synthesis of membrane-forming compounds.

The synthesis of palmitoylglycerols in good yields occurs when a solution of glycerol, ammonium palmitate, cyanamide and imidazole is dried and heated at ambient humidity at temperatures ranging from 60 degrees--100 degrees C for 16 h. Much less product is formed in the absence of either or both cyanamide or imidazole. This work suggests that acylglycerols could have been synthesized on the primitive Earth under plausible prebiotic conditions which were similar but not identical to those which have been shown to condense deoxynucleotides into oligodeoxynucleotides and amino acids into peptides.

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.

One of the major diagenetic pathways of organic matter in recent sediments involves the condensation of cellular constituents, particularly amino acids and sugars, into insoluble melanoidin-type polymers. These polymers consist mainly of humic and fulvic acids and make up the major part of the organic carbon reservoir in recent sediments. We suggest that a similar set of reactions between abiotically formed amino acids and sugars, and more generally between aldehydes and amines, occurred on a large scale in the prebiotic hydrosphere. The rapid formation of this insoluble polymeric material would have removed the bulk of the dissolved organic carbon from the primitive oceans and would thus have prevented the formation of an "organic soup". Melanoidin polymers have several properties which make them attractive hypothetical precursors of contemporary oxidation-reduction coenzymes: 1. they contain heterocyclic nitrogen compounds similar to the nitrogenous bases; 2. they contain a high concentration of stable free radicals; and 3. they tend to concentrate those heavy metals which play prominent roles in contemporary enzymic redox processes. The prebiotic formation of similar polymers could, therefore, have provided the starting point for a basic class of biochemical reactions. We suggest that the prebiotic scenario involved chemical and protoenzymic reactions at the sediment-ocean interface in relatively shallow waters and under conditions not much different from those of the recent environment.

Two studies on the abiotic formation of amino acids are presented. The first study demonstrates the role of hydrogen cyanide as a precursor of amino acids detected in extracts of lunar samples. The formation of several amino acids, including glycine, alanine, aspartic acid, and glutamic acid, under conditions similar to those used for the analysis of lunar samples is demonstrated. The second study investigates the formation of hydrogen cyanide as well as amino acids from lunar-sample gas mixtures under electrical discharge conditions. These results extend the possibility of synthesis of amino acids to planetary bodies with primordial atmospheres less reducing than a mixture of methane, ammonia, hydrogen and water.

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.

Using the model of a primitive earth evaporation pond, the synthesis of three histidyl peptides in yields up to 11% was demonstrated when aqueous solutions of histidine, leucine, ATP, cyanamide, and MgCl2 were evaporated and heated for 24 h at 80 degrees C. In addition, peptides were formed in yields of up to 56%, 35%, and 21%, respectively for phenylalanine, leucine, and alanine when aqueous solutions of the appropriate amino acid were evaporated and heated with cyanamide and one or more of the following components: ATP, AMP, 4-amino-5-imidazole carboxamide, or MgCl2. The greatest peptide yield occurred at pH 3. But peptide formation was demonstrated for a system of Leu, cyanamide, and MgCl2 adjusted to pH 7 with NH4OH. Peptide synthesis was also studied in the presence of CaCl2, ZnCl2, different adenosine nucleotides, and UTP to compare their effects on peptide synthesis. The optimum conditions for cyanamide mediated peptide synthesis were also studied in terms of pH, reaction time, reaction temperature, and cyanamide concentration. The major side product in nearly all reactions studied appears to be an amino acid-cyanamide adduct. Peptides were analyzed and identified by thin layer chromatography, acid hydrolysis, and enzymatic degradation.

Peptides were formed in yields of 5%, 17% and 66%, respectively, when aqueous solutions of glycine, isoleucine or phenylalanine were dried and heated for 24 h at 90 degrees C with adenosine 5'-triphosphate, 4-amino-5-imidazolecarboxamide and cyanamide. Glycine and L-phenylalanine produced mixtures of di-, tri- and tetrapeptides, while L-isoleucine gave only the dipeptide in detectable quantities. The dipeptides of L-isoleucine and L-phenylalanine were identified by mass spectrometry and enzymatic and enzymatic degradation.

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 (

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.

Analyses of sedimentary rocks from the Pre-Cambrian of South Africa show that they contain a variety of alkanes. Were these hydrocarbons incorporated into the sediments at the time of sedimentary deposition, and are they biogenic in origin ?

This paper is primarily a review of recent developments in the abiotic synthesis of nucleotides, short chain oligonucleotides, and their mode of replication in solution. It also presents preliminary results from this laboratory on the prebiotic synthesis of thymidine oligodeoxynucleotides. A discussion, based on the physicochemical properties of RNA and DNA oligomers, relevant to the molecular evolution of these compounds leads to the tentative hypothesis that oligodeoxyribonucleotides of about 12 units may have been of sufficient length to initiate a self replicating coding system. Two models are suggested to account for the synthesis of high molecular weight oligomers using short chain templates and primers.

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.

Following the procedure of Schramm for the synthesis of polynucleotides and polysaccharides, homopolymers ofdl-leucine,dl-phenylalanine,dl-serine, anddl-valine have been prepared in yields of 13 to 57 % through the mediation of a polymetaphosphate ester. Copolymers of the amino acids also have been prepared in lower yields (4–5 %). Infrared spectra show that the polymers are not diketopiperazines and that the polymers ofdl-leucine,dl-phenylalanine, anddl-valine are polypeptides. Conversions of as much as 57% and degrees of polymerization of approximately 12 were obtained for polyleucine. Small peptides containing possibly 2 to 3 leucine residues were detected and isolated as possible intermediates in the leucine polymerization reaction. For the polymerization ofdl-valine, a temperature of 60°C, a reaction time of 10–24 h, and a ratio of polymetaphosphate ester to amino acid of 3:1 appeared to give the best results. The Schramm procedure was initially suggested as a chemical evolution model for the formation of biological polymers under prebiotic conditions. Although the significance of this reaction to prebiological organic chemistry may be questioned, it still offers a mechanistic model for the study of the synthetic reactions involving polyphosphates which are indirectly relevant to abiotic molecular evolution and the problem of the origin of life.

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.

Gas chromatography and combined gas chromatography-mass spectrometry have been used to study the fatty acids and hydrocarbons of a bacterium from the Pacific Ocean,Vibrio marinus, a freshwater blue-green alga,Anacystis nidulans, and algal mat communities from the Gulf of Mexico. Both types of microorganisms (bacteria and algae) showed relatively simple hydrocarbon and fatty acid patterns, the hydrocarbons predominating in the region of C-17 and the fatty acids in the range of C-14 to C-18. The patterns ofV. marinuswere more comparable to those of the algal populations than to patterns reported for other bacteria. An incomplete correlation between fatty acids and hydrocarbons in both types of organisms was observed, making it difficult to accept the concept that the biosynthesis of hydrocarbons follows a simple fatty acid decarboxylation process.

The nonpolar (acetone-soluble) lipids of the extremely halophilic bacterium, Halobacterium cutirubrum, were found to consist of red carotenoid pigments (43%) and squalenes (48%) with a small amount of a vitamin K-type quinone. The squalenes were shown by n.m.r. and mass spectra to consist of the fully isoprenoid squalene (S; C3OH5o), dihydrosqualene (S2; CJ&152), and tetrahydrosqualene (S4; C30H54) in the ratio of 1.0:0.4:0.1. S2 probably has one re- duced internal isoprenoid group, and S4 has one internal and one terminal reduced isoprenyl group. The vitamin K-type quinone was shown by n.m.r. and mass spectra to have a Cho isoprenoid side chain, and is thus identified as menaquinone-8 (MK-8).

The liver oil from the South American Basking shark has been fractionated by silica gel chromatography and analyzed by the new method of combined gas-chromatography mass spectrometry. The major compounds of the nonsaponifiable fraction are pristane and squalene, which account for 7.6 and 31.3% of the oil. The saponifiable fraction contains normal fatty acids from C14 to C22; the four major components are palmitic, oleic, and the monounsaturated eicosenoic and docosenoic acids. No correlation was observed between the hydrocarbons (essentially all isoprenoid derivatives) and the fatty acids (essentially all normal) of this oil. The same treatment was applied to a sample of commercial pristane which was obtained from Basking shark liver oil. It was found to contain about 1% phytane and small amounts of octadecane, nonadecane, and methyl and ethyl palmitates. Mass spectral data for squalene are presented for the first time along with the low electron energy-mass spectra for pristane and phytane.

Non-enzymicβ-decarboxylation of aspartic acid at 85° is catalyzed by Al(3+) and pyridoxal. The reaction is optimum at pH 4.0. Both Al(3+) and pyridoxal are specifically required because replacing these by other cations or by other vitamin B6 derivatives greatly lowers the formation of alanine. Conversion of 8 µmoles of aspartic acid to alanine is optimum in presence of 1µmole of Al(3+) and 5 µmoles of pyridoxal. Increasing the concentration of pyridoxal to more than 5 µmoles lowers the alanine formation by the latter being converted to pyruvate by transamination with the excess pyridoxal.Studies on the mechanism of decarboxylation suggest that aspartic acid is first converted to oxalacetic acid by transamination with pyridoxal which in turn is converted to pyridoxamine. This is followed by decarboxylation of oxalacetic acid to form pyruvic acid which transaminates with pyridoxamine to form alanine. The results are interpreted to suggest that the non-enzymic aspartateβ-decarboxylation process is closely related to and inseparable from the non-enzymic transamination process in a manner analogous to that reported for the highly purified asparateβ-decarboxylase. The possible significance of these results to prebiotic molecular evolution is briefly discussed.

The gas chromatographicmass spectrometric technique recently developed by Ryhage has been applied to the analysis of paraffins extracted from pasture plants, specifically, whole plant and leaves of spotted bur clover (Medicago arabica). Normal alkanes from C(18) to C(35) have been found. The C(29), C(31), and C(33) normal saturated hydrocarbons predominate and n-C(31) is the major component. In the range from C(24) to C(34) the ratio of alkanes with an even number of carbon atoms to those with an odd number is approximately 8 for the whole plant and 5 for the leaves. The distribution of paraffins is similar to that reported for cattle manure and also resembles that of some soils and sediments.

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.

It is shown that the explanation of terrestrial contamination of the Murchison meteorite is consistent with the analysis of extracts from the meteorite reported by Engel and Nagy (EN) (1982) and is much more probable than their suggestion that the excess of L-enantiomers for several protein amino acids is due to asymmetric synthesis or decomposition. The low abundance of serine and threonine reported by EN may be due to their decomposition during the derivatization procedure, and the absence of methionine, tyrosine, and phenylalanine can be attributed to various causes. The amount of contamination in EN's extracts are estimated from a mass balance of the amino acid enantiomers, and it is found that the amino acids in the HCl could be due entirely to contamination while in the water extract the amount of contamination ranges from about 40 to 97 percent, depending on the amino acid. The argument that contaminants were preferentially extracted by EN's procedure cannot account for the failure to detect methionine, tyrosine, and phenylalanine.

The hydrocarbon composition of two algae, a golden-brown (Bot-ryococcus braunii) and a blue-green (Anacystis montana), has been investigated by gas chromatography-mass spectrometry. Both show distributions of aliphatic hydrocarbons of odd carbon numbers in the medium and high ranges of molecular weight, with maxima at n-C(17) and n-C(29) for B. braunii and n-C(17) and n-C(29) for A. montana. With the exception of the n-heptadecane of A. montana all the hydrocarbons are monoenes, dienes, or trienes. Since certain continental sediments and oils show similar distributions of alkanes with respect to carbon number, these organisms may be the precursors of the hydrocarbons in these formations.

An unusual mode of distribution of low-molecular-weight n-alkanes (C11-C15) with a slight even carbon-number predominance has been observed in the gas Chromatographic analysis of the paraffin fraction which was extracted from the wool of live sheep. This is in addition to the other two modes of medium-, C15-C24, and high-, C24-C33, molecular-weight alkanes usually present in wool wax which have also been found in sheep’s manure. The high-molecular-weight hydrocarbons (predominantly odd carbon-numbered) are presumed to be derived from the diet (pasture plants) whereas the other two hydrocarbon distributions probably result from the combined action of animal and microbial metabolism.

Arenes of 1, 2, 3, 4 and more rings have been synthesized in a flow system by passing methane through silica gel at 1000 degrees C. Yields of 4.8 to 7.2 percent have been obtained per single pass. As determined by combined gas chromatography-mass spectrometry, the major compound synthesized that are of less than S rings are benzene, naphthalene, acenaphthylene, phenanthrene, fluoranthene, and pyrene. Under certain conditions ( presence of ammonia and water), small amounts of aliphatic hydrocarbons are also synthesized. Even-carbon-numbered hydrocarbons (aromatic as well as aliphatic) predominate, to the extent that about 97 percent of the total weight of the analyzed arenes have even numbers of carbon atoms.

The condensation of thymidine-5′-monophosphate was carried out in the presence of imidazole in aqueous solutions at neutral pH. Formation of oligo-deoxyribonucleotides up to four units was observed.

When an aqueous solution (pH 7.0) of deoxythymidine 5'-phosphate, 4-amino-5-imidazolecarboxamide and cyanamide was dried and heated for 18 h at 60 degrees C, P1, P2-dideoxythymidine 5'-pyrophosphate (I) was formed in a 58% yield. Oligonucleotides were not detected in the reaction product. Under conditions employed in the above reaction, (I) was shown to be stable. In prebiotic polymerization reactions employing deoxythymidine 5'-triphosphate as the polymerizing species, (I) could therefore function as a primer and minimize the formation of cyclic nucleotides.

Cosmochemical considerations suggest various potential sources for the accumulation of organic matter on Mars. However the Viking Molecular Analysis did not indicate any indigenous organic compounds on the surface of Mars. Their disappearance from the top layer is most likely caused by the combined action of the high solar radiation flux and various oxidizing species in the Martian atmosphere and regolith. In this study the stability of several organic substances and a sample of the Murchison meteorite was tested under simulated Martian conditions. After adsorption on powdered quartz, samples of adenine, glycine and naphthalene were irradiated with UV light at various oxygen concentrations and exposure times. In the absence of oxygen, adenine and glycine appeared stable over the given irradiation period, whereas a definite loss was observed in the case of naphthalene, as well as in the volatilizable and pyrozable content of the Murchison meteorite. The presence of oxygen during UV exposure caused a significant increase in the degradation rate of all samples. It is likely that similar processes have led to the destruction of organic materials on the surface of Mars.

A mixture of ammonium palmitate, 14C-sn-glycero-1(3)-phosphate, cyanimide and imidazole when heated for several hours formed significant quantities of phospholipids. These reaction products were shown by chromatographic, chemical and enzymatic procedures to be monopalmitoylglycerophosphate (MPGP), dipalmitoylglycerophosphate (DPGP) and monopalmitoyl cyclic glycerophosphate (cMPGP). A portion of the MPGP and DPGP possessed the same steric configuration as naturally occurring lysophosphatidic acid and phosphatidic acid. The yield of total phospholipid was maximal at temperatures between 60 degrees and 90 degrees after 8 h. When ratios of reactants were varied, up to 45% of radioactive glycerophosphate was converted into phospholipids. The average proportions of individual phosphatidic acids were: 60% MPGP, 27% DPGP and 13% cMPGP. Evidence was obtained for a synergistic relationship between cyanamide and imidazole in promoting the formation of phosphatidic acids. These results suggest that phosphatidic acids, which are essential precursors for the biochemical synthesis of more complex membrane phospholipids, could have been produced on the primitive Earth.

The prebiotic synthesis of imidazole-4-acetaldehyde and imidazole-4-glycol from erythrose and formamidine has been demonstrated as well as the prebiotic synthesis of imidazole-4-ethanol and imidazole-4-glycol from erythrose, formaldehyde and ammonia. The products were identified by TLC, HPLC, and LC-MS by comparison with authentic samples. The maximum yields of imidazole-4-acetaldehyde, imidazole-4-ethanol, and imidazole-4-glycol obtained in these reactions are 1.6, 5.4, 6.8% respectively, based on the erythrose. Imidazole-4-acetaldehyde would have been converted to histidine on the primitive earth by a Strecker synthesis, and several prebiotic reactions would convert imidazole-4-glycol and imidazole-4-ethanol to imidazole-4-acetaldehyde.

Publisher Summary This chapter reviews a personal account of J. Oro on pre-biological chemistry and the origin of life. By having the insight and wisdom to follow the thread of the biochemistry of high energy phosphate and working with vigor and imagination, Severo Ochoa has been a pioneer or major contributor in many of the above discoveries. These major advances together with the contributions of Mendelian and molecular genetics have provided a clear understanding of the basic principles that govern all living organisms and have demonstrated the fundamental unity of terrestrial life, as required by Darwin's theory of biological evolution. As pointed out by Miller, the similar experiment performed earlier by W. Loeb was done in an entirely different context in an unsuccessful attempt to provide a chemical model for the mechanisms of nitrogen fixation and amino acid biosynthesis in plants. Besides hydroxy acids, urea and other organic compounds, some of the most abundant biological amino acids obtained by Miller in these experiments were glycine, alanine, and aspartic acid.

Publisher Summary This chapter discusses energy conversion in the context of the origin of life. Electric discharges appear to be not only the most efficient method for amino acid synthesis but also yield a mixture of amino acids that qualitatively and quantitatively is the same as that found in the Murchison carbonaceous chondrite. Electric discharges would also have been important in synthesizing hydrogen cyanide, a central intermediate in prebiotic syntheses of amino acids and purines, and in synthesizing cyanoacetylene, which is a required intermediate for the prebiotic synthesis of pyrimidines. The ultraviolet light is also likely to have played a major role in prebiotic synthesis. The energy in the sun's spectrum that can be absorbed by the major constituents of the primitive atmosphere is not particularly large. However, trace constituents such as HLS and formaldehyde absorb at longer wavelengths where a great deal of energy is available. An example of using these longer wavelengths is the synthesis of amino acids from the hot hydrogen atoms produced on the photolysis of H2S, which break up the CH4, NH3, and H2O molecules even though these molecules do not absorb at these wavelengths.

The analysis of the top layer of the Martian regolith at the two Viking landing sites did not reveal any indigenous organic compounds. However, the existence of such compounds at deeper layers cannot be ruled out. Cosmochemical considerations indicate various potential sources for organic matter on Mars, such as comets and meteorites. The study tested the stability of a sample of the Murchison meteorite and various organic substances which have been detected in carbonaceous chondrites, such as glycine, adenine and naphthalene, to the action of ultraviolet light. The compounds were adsorbed on powdered quartz and on California desert soil and were irradiated in the presence or absence of oxygen. The organic content, before and after irradiation, was measured by carbon elementary analysis, UV-absorption, amino acid analysis or pyrolysis-gas chromatography-mass spectrometry. In the absence of oxygen, adenine and glycine appear to be stable over the given part of irradiation. A definite degradation was noticed in the case of naphtalene and the Murchison meteorite. In the presence of oxygen in amounts comparable to those on Mars all compounds were degraded. The degree of degradation was influenced by the irradiation time, temperature and oxygen content.

It has been estimated that during its early history the earth captured a mass of cometary material of the order of 10 to the 23rd grams. Since carbon is supposed to be at least three times more abundant in comets than in carbonaceous chondrites (3.5 percent C in C 1 chondrites), it can be deduced that about 1 x 10 to the 22nd grams of carbon (as carbon compounds), were added by comets to the surface of the prebiotic earth. This carbon value is of the same order of magnitude as the value of the organic carbon buried in the earth's sedimentary shell, but approximately one order of magnitude lower than the earth's surface total carbon (7 x 10 to the 22nd gm). The capture of comets by the earth would also have contributed to generating the appropriate aqueous and reducing environmental conditions necessary for organic synthesis.

A variety of methods have been investigated in different laboratories for the polymerization of amino acids and nucleotides under abiotic conditions. They include (1) thermal polymerization; (2) direct polymerization of certain amino acid nitriles, amides, or esters; (3) polymerization using polyphosphate esters; (4) polymerization under aqueous or drying conditions at moderate temperatures using a variety of simple catalysts or condensing agents like cyanamide, dicyandiamide, or imidazole; and (5) polymerization under similar mild conditions but employing activated monomers or abiotically synthesized high-energy compounds such as adenosine 5'-triphosphate (ATP). The role and significance of these methods for the synthesis of oligopeptides and oligonucleotides under possible primitive-earth conditions is evaluated. It is concluded that the more recent approach involving chemical processes similar to those used by contemporary living organisms appears to offer a reasonable solution to the prebiotic synthesis of these biopolymers.

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

In the past decade significant advances have been made in the synthesis of oligonucleotides and other polymers by means of imidazoles and other condensing agents. In spite of the current knowledge of the chemistry of imidazoles and their importance as prebiotic catalysts, their formation under primitive earth conditions has not been properly demonstrated. We have now been able to synthesize imidazole as well as its 2-methyl and 4-methyl derivatives under plausible prebiotic conditions. One method utilizes an aldehyde (formaldehyde or acetaldehyde), glyoxal and ammonia as the starting materials for the formation of imidazole and 2-methylimidazole. The other method uses a carbohydrate and ammonia as the key reagents for the synthesis of 4-methylimidazole. The importance of imidazole and related compounds (e.g., cyanamide) in the synthesis of oligonucleotides has been studied by us as well as others. Apparently the charge relay group (−N−C−N−) present in imidazoles, carbodiimides, cyanamide, or the histidine and arginine of enzyme active centers is essential for the synthesis of phosphodiester and pyrophosphate bonds.

Some of the chemical species which have been detected in comets include H2O, HCN, CH3CN, CO, CO2, NH3, CS, C2 and C3. All of these have also been detected in the interstellar medium, indicating a probable relationship between interstellar dust and gas clouds and comets. Laboratory experiments carried out with different mixtures of these molecules give rise to the formation of the biochemical compounds which are necessary for life, such as amino acids, purines, pyrimidines, monosaccharides, etc. However, in spite of suggestions to the contrary, the presence of life in comets is unlikely. On the other hand, the capture of cometary matter by the primitive Earth is considered essential for the development of life on this planet. The amount of cometary carbon-containing matter captured by the Earth, as calculated by different authors, is several times larger than the total amount of organic matter present in the biosphere (10(18)g). The major classes of reactions which were probably involved in the formation of key biochemical compounds are discussed. Our tentative conclusions are that: 1) comets played a predominant role in the emergence of life on our planet, and 2) they are the cosmic connection with extraterrestrial life.

Using the model of a primitive earth evaporating pond, peptides were formed in yields of up to 21%, 30% and 35%, respectively for alanine, phenylalanine, and leucine when aqueous solutions of the appropriate amino acid were evaporated and heated for 24 hrs at 80°C with cyanamide and one or more of the following components; adenosine 5′-triphosphate, 4-amino-5 imidazole carboxamide, or MgCl2. The greatest peptide yield was achieved at about pH 3. But peptide formation was demonstrated for a system of leu, cyanamide and MgCl2 adjusted to pH 7 with NH4OH. The incorporation of radioactive amino acids into products was found to be increased in the presence of MgCl2 at all pH’s studied, which ranged from 3 to 7. The major side product in all reactions appears to be an amino acid-cyanamide adduct. The peptides were analyzed and identified by thin layer chromatography, acid hydrolysis, and enzymatic degradation.