One of the foremost experiments of the twentieth century : Stanley Miller and the origin of prebiotic chemistry

Stanley Miller is best known for his classic 1953 experiment on the synthesis of early Earth organic compounds, in the context of the origins of life. However, he did several other experiments that are lesser known and, in some cases, have never been published. The finding in 2007 that Miller had archived dried solutions from his 1950s experiments offered the opportunity of analyzing the products of his early experiments using modern day state-of-the-art techniques. These results, along with Miller?s results, have provided an inventory of the large variety of compounds that include amino acids, amines, simple peptides, hydroxy acids, simple hydrocarbons and urea, which can be synthesized under simulated early Earth conditions

The Chemistry of Early Self-Replicating Systems

The NASA Specialized Center of Research and Training (NSCORT) in Exobiology is a consortium of scientists at the University of California at San Diego (UCSD), The Salk Institute for Biological Studies (Salk) and The Scripps Research Institute (TSRI). All three institutions are located in close geographical proximity in La Jolla, California. The NSCORT/Exobiology is administered through the Scripps Institution of Oceanography. Since its inception in January 1992, the NSCORT in Exobiology has made major contributions with respect to the question of how life began on Earth. The Principal Investigators (PIs) and their associated Fellows have published numerous articles in peer reviewed journals on topics relevant to Exobiology. They have presented papers and sponsored symposia at several meetings of national and international scientific societies. A total of 30 undergraduate, 12 graduate and 15 postdoctoral Fellows have been supported by the NSCORT. The Fellows have met on their own at least once a month to discuss Exobiology topics and research progress. The NSCORT has arranged seminars and evening discussion meetings, and offered an undergraduate class on "Biochemical Evolution" as well as graduate courses dealing with topics in Exobiology. A visiting scientist program has allowed 11 scientists from the U.S. and 4 foreign countries to conduct cooperative research with the various PIs. An active outreach program has been initiated, which includes an Exobiology high school level teaching module and curriculum guide, and an elementary school level booklet about basic atomic structure and formation of the universe, Sun and Earth. A World Wide Web Homepage (http://www-chem.ucsd.edu/-nscort/ NSCORT.html) has been developed, which describes the NSCORT activities, research programs and Fellowship opportunities. The various activities of the NSCORT in Exobiology have received wide-spread coverage in both the scientific and public media. The major function of the NSCORT is the training of young scientists in the field of Exo- biology. Thus, the bulk of the $1,000,000 annual budget is used to support the research and training of undergraduate, graduate and post-doctoral Fellows who are selected on a competitive basis. About five Fellows at each level are supported each year. Our goal is to train scientists whose major research interest is Exobiology, but whose mastery in the classical fields of chemistry, biology and earth science is so strong that they outstanding candidates for either graduate school or academic tenure-track positions in departments at leading national and international Universities. Applicants for these Fellowships are solicited by advertisements in journals such as Science and Nature and in organizational newsletters such as the one published by the International Society for the Study of the Origin of Life (ISSOL), by contacting academic and NASA colleagues working in Exobiology or related fields and by recruiting students who have already been admitted into the various academic programs with which the PIs are affiliated

Oxalic, glyoxalic and pyruvic acids in eastern Pacific Ocean waters

A sensitive high performance liquid chromatographic (HPLC) technique has been used to determine the concentration and distribution of several α-keto acids and oxalic acid in seawater samples from a station (28°29′N, 128°38′W) in the eastern Pacific Ocean. Glyoxalic, pyruvic and oxalic acids were found to be present. Although the pyruvic acid profile at this station was in general featureless, the profiles for glyoxalic and oxalic acids showed variations which could be attributed to both primary production and heterotropic activity. Surface waters were found to have a combined concentration of glyoxalic and oxalic acids of ∼300 to 400 nm/liter which makes these two compounds some of the more abundant organic constituents of surface ocean waters

Determination of (alpha)-dialkylamino acids and their Enantiomers in Geological Samples by High-Performance Liquid Chromatography after Dervatization with a Chiral Adduct of (omicron)-Phthaldialdehyde

Derivatization with (omicron)-phthaldialdehyde (OPA) and the chiral thiol N-acetyl-L-cysteine (NAC) is a convenient and sensitive technique for the HPLC detection and resolution of protein amino acid enantiomers. The kinetics of the reaction of OPA-NAC with (alpha)-dialkylamino acids was investigated. The fluorescence yield of (alpha)-dialkylamino acids was only about 10% of that of protein amino acids when the derivatization was carried out at room temperature for 1-2 min, which is the procedure generally used for protein amino acid analyses. The fluorescence yield of (alpha)-dialkylamino acids can be enhanced by up to ten-fold when the derivatization reaction time is increased to 15 min at room temperature. The OPA-NAC technique was optimized for the detection and enantiomeric resolution of a-dialkylamino acids in geological samples which contain a large excess of protein amino acids. The estimated detection limit for a-dialkylamino acids is 1-2 pmol, comparable to that for protein amino acids

A Reexamination of Amino Acids in Lunar Soils: Implications for the Survival of Exogenous Organic Material During Impact Delivery

Using a sensitive high performance liquid chromatography technique, we have analyzed both the hot water extract and the acid hydrolyzed hot water extract of lunar soil collected during the Apollo 17 mission. Both free amino acids and those derived from acid labile precursors are present at a level of roughly 15 ppb. Based on the D/L amino acid ratios, the free alanine and aspartic acid observed in the hot water extract can be entirely attributed to terrestrial biogenic contamination. However, in the acid labile fraction, precursors which yield amino acids are apparently present in the lunar soil. The amino acid distribution suggests that the precursor is probably solar wind implanted HCN. We have evaluated our results with regard to the meteoritic input of intact organic compounds to the moon based on an upper limit of less than or equal to 0.3 ppb for alpha-aminoisobutyric acid, a non-protein amino acid which does not generally occur in terrestrial organisms and which is not a major amino acid produced from HCN, but which is a predominant amino acid in many carbonaceous chondrites. We find that the survival of exogenous organic compounds during lunar impact is less than or equal to 0.8%. This result represents an example of minimum organic impact survivability. This is an important first step toward a better understanding of similar processes on Earth and on Mars, and their possible contribution to the budget of prebiotic organic compounds on the primitive Earth

Detecting Amino Acids on Mars

Understanding the events that led to the origin of life on Earth is complicated by the lack of geological evidence from the period around four billion years (4 Gyr) ago when the transition from prebiotic chemistry to biochemistry is believed to be occurred. Although erosion and plate tectonics have since erased the terrestrial geological record from the time of the origin of life, there is possibility that information about this period of Earth history may still be preserved on Mars. A major goal of the NASA Space Exploration Program is to search for evidence of abiotic chemistry and extinct or extant life on Mars. During the next decade, spacecraft will orbit Mars, land on the surface, and return with surface samples for analysis. The question is what compounds should we search for, either directly on the planet or in samples returned to Earth, that will answer unambiguously whether abiotic and/or biotic organic molecules are present

Hypervelocity impact survivability experiments for carbonaceous impactors

We performed a series of hypervelocity impact experiments using carbon-bearing impactors (diamond, graphite, fullerenes, phthalic acid crystals, and Murchison meteorite) into Al plate at velocities between 4.2 and 6.1 km/s. These tests were made to do the following: (1) determine the survivability of carbon forms and organize molecules in low hypervelocity impact; (2) characterize carbonaceous impactor residues; and (3) determine whether or not fullerenes could form from carbonaceous impactors, under our experimental conditions, or survive as impactors. An analytical protocol of field emission SEM imagery, SEM-EDX, laser Raman spectroscopy, single and 2-stage laser mass spectrometry, and laser induced fluorescence (LIF) found the following: (1) diamonds did not survive impact at 4.8 km/s, but were transformed into various forms of disordered graphite; (2) intact, well-ordered graphite impactors did survive impact at 5.9 km/sec, but were only found in the crater bottom centers; the degree of impact-induced disorder in the graphite increases outward (walls, rims, ejecta); (3) phthalic acid crystals were destroyed on impact (at 4.2 km/s, although a large proportion of phthalic acid molecules did survive impact); (4) fullerenes did not form as products of carbonaceous impactors (5.9 - 6.1 km/s, fullerene impactor molecules mostly survived impact at 5.9 km/s; and (5) two Murchison meteorite samples (launched at 4.8 and 5.9 km/s) show preservation of some higher mass polycyclic aromatic hydrocarbons (PAHs) compared with the non-impacted sample. Each impactor type shows unique impactor residue morphologies produced at a given impact velocity. An expanded methodology is presented to announce relatively new analytical techniques together with innovative modifications to other methods that can be used to characterize small impact residues in LDEF craters, in addition to other acquired extraterrestrial samples

Extraterrestrial Helium Trapped in Fullerenes in the Sudbury Impact Structure

Fullerenes (C60 and C70) in the Sudbury impact structure contain trapped helium with a He-3/He-4 ratio of 5.5 x 10(exp -4) to 5.9 x 10(exp -4). The He-3/He-4 ratio exceeds the accepted solar wind value by 20 to 30 percent and is higher by an order of magnitude than the maximum reported mantle value. Terrestrial nuclear reactions or cosmic-ray bombardment are not sufficient to generate such a high ratio. The He-3/He-4 ratios in the Sudbury fullerenes are similar to those found in meteorites and in some interplanetary dust particles. The implication is that the helium within the C60 molecules at Sudbury is of extraterrestrial origin

Investigation of the Prebiotic Synthesis of Amino Acids and RNA Bases from CO2 Using FeS/H2S As a Reducing Agent

An autotrophic theory of the origin of metabolism and life has been proposed in which carbon dioxide is reduced by ferrous sulfide and hydrogen sulfide by means of a reversed citric acid cycle, leading to the production of amino acids. Similar processes have been proposed for purine synthesis. Ferrous sulfide is a strong reducing agent in the presence of hydrogen sulfide and can produce hydrogen as well as reduce alkenes, alkynes, and thiols to saturated hydrocarbons and reduce ketones to thiols. However, the reduction of carbon dioxide has not been demonstrated. We show here that no amino acids, purities, or pyrimidines are produced from carbon dioxide with the ferrous sulfide and hydrogen sulfide system. Furthermore, this system does not produce amino acids from carboxylic acids by reductive amination and carboxylation. Thus, the proposed autotrophic theory, using carbon dioxide, ferrous sulfide, and hydrogen sulfide, lacks the robustness needed to be a geological process and is, therefore, unlikely to have played a role In the origin of metabolism or the origin of life