Report Nsec- 118
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c REPORT NSEC- 118 REPORT A STUDY ON THE ROLE OF RADIOACTIVITY AND HYDROTHERMAL PROCESSES IN PROTOBIOCHEMSTRY R. L. Bogner S. L. Hood E. R. White S. Somani June 1965 Submitted to: Office of Space Science and Applications Bioscience Programs Division National Aeronautics and Space Administration Contract No. NASW-989 NUCLEAR SCIENCE & ENGINEERING CORPORATION P. 0. Box 10901 Pittsburgh, Pennsylvania 15236 PREFACE This study was conducted under Contract No. NASW-989 for the Office of Space Sciences, National Aeronautics and Space Administration. Program direction was provided by Dr. R. R. Edwards, Technical Director. The authors wish to acknowledge the technical assistance of Dr. R. C. Koch and Philip Battaglia. The cooperation of Dr. R. Lumb and P. Orlosky at the Western New York Nuclear Research Center in Buffalo, and Mr. Robert Reitz at the Mellon Institute in Pittsburgh is also acknowledged. Grateful appreciation is expressed for the opportunities to discuss aspects of this work with Dr. Carl Bruch, Bioscience Programs, Office of Space Sciences, NASA, Dr. Sidney W. Fox, School of Environmental and Planetary Sciences, University of Miami, Dr . Cyril Ponnamperuma, Exobio- logy Division, NASA, Ames Research Center, Dr. Paul Kuroda, Department of Chemistry, University of Arkansas, and Dr. Truman P. Kohman, Depart- ment of Chemistry, Carnegie Institute of Technology. ii ABSTRACT This report describes the initial phases of a study designed to test the novel and unique hypothesis that organic synthesis and chemical evolution in primitive planetary environments may have proceeded in radioactive hydro- thermal systems. It was demonstrated that an abundance of biochemically significant organic compounds can be formed from the simplest chemical resources in hot, aqueous environments under the influence of ionizing radia- tion. Furthermore, it was shown that high-molecular weight peptides and proteinoids can be produced in the same unique model system thus providing mechanisms for the generation of macromolecules, an essential development for the evolutionary progression from chemical simplicity to prebiotic molecu- lar complexity. This experimental verification of the possible geological origin of biochemical substances (chemical abiogenesis) suggests that spon- taneous primordial chemical reactions might well have led to the production and proliferation of organic molecules in favorable local environments, e. g. hot springs, early in the history of the planet Earth. These ground-based studies assume an immediate significance for lunar and planetary exploration in view of the fact that propitious geochemical events and conditions on the moon and Mars, similar to those present earlier in the history of the Earth, may provide primitive hydrothermal radioactive systems in which abiogenic formation of extraterrestrial organic compounds proceeds at present. iii TABLE OF CONTENTS Page PREFACE ii ABSTRACT iii LIST OF TABLES iv LIST OF FIGURES V INTRODUCTION 1 EXPERIMENTAL 3 I. Methods 3 11. Results 8 I DISCUSSION 21 SUMMARY 42 BIBLIOGRAPHY 43 TABLES 48 FIGURES 59 TABLES Page Table I Experimental conditions 48 Table I1 Composition of reaction mixtures 49 Table I11 Columns for gas chromatography 50-51 Table IV Summary of chemical classes produced from 52 primitive earth compounds Table V Gas chromatographic data from Experiments 53 6 to 11 I Table VI One-dimensional paper chromatographic data 54 from Experiments 6 to 11 Table VI1 One-dimensional paper chromatography: 55 Numbers of spots from chromium carbide Table VIII Compounds from irradiation of aqueous methane, 56 Experiment 20 Table IX Compounds from irradiation of aqueous acetylene, 57 Expe riment 2 2 Table X Amino acids from irradiated experiments 58 iv FIGURES Page Figure 1. Photomicrograph of amber, protein-like 59 spherule s precipitated from an irradiated aqueous amino acid solution, Experiment 12 Figure 2. Autoradiogram of methanol-C- 14 irradiation 60 products, Experiment 10 Figure 3. Autoradiogram of methanol-C- 14 irradiation 61 products after removal of volatile compounds Figure 4. Autoradiogram of irradiation products from 62 formate-C- 14, Experiment 14 Figure 5. Autoradiogram of irradiation products from 63 formate-C- 14 in the presence of FeCl 3’ Experiment 16 V IN TROD UC TION Investigations of protobiochemistry, "origin of life", are generally con- cerned with studies of organic synthesis and chemical evolution under simulated primitive planetary environments. Protobiochemistry is under stood to be the process by which organic chemical compounds of the types found in present day biological organisms are formed in the absence of life (abiogenically) by normal chemical processes which occur in a particular environment and using as raw materials simple inorganic and one-carbon organic chemicals which could have existed on the primitive earth. Such investigations involve making assumptions about the nature of conditions on the earth approximately 4 to 5 billion years ago, setting up analogous model systems in the laboratory, and examining these systems for the production of biochemical type compounds. Indeed, evidence to suggest that abiogenic formation of basic biochemicals may have occurred on the primitive earth or in space has been obtained from several studies of a variety of model systems with various energy sources. However, no general scientific agreement has been reached on the probable system and pattern that actuaiiy was responsibie for primordiai synthesis and chemicai evolution. The significance of hydrothermal processes in experimental protobio- chemistry has received surprisingly little attention, this in spite of the ubiquitous hydrothermal activity of the primitive earth, the associated energy sources due to the high levels of radioactivity, and the presence of earth's most primitive known organisms in modern hydrothermal waters, From our current knowledge, it seems entirely reasonable to speculate that radioactivity and hydrothermal processes played an important role in the origin of life. Such a model provides for more than an adequate amount of inorganic chemical resources and energy (heat and ionizing radiation) in local regions and in satisfactory sequences of conditions (hydrous and anhydrous) that would be exceedingly favorable to chem- ical evolution and prebiological development. - 1- I It would appear reasonable to direct protochemical research to models I of attractive and favorable local environments rather than to concentrate upon I studies which find it necessary to consider equilibrium conditions evenly dis- I tributed throughout the planet, particularly if it is agreed that the origins of life probably represented low-probability, isolated events. The scope of the present study, then, was to undertake a research pro- gram aimed at developing the consistencies of a model, incorporating radio- activity and hydrothermal processes, with other knowledge in regard to protobiochemistry. The initial program was aimed at exploring syntheses under the conditions of the model, beginning with a hot aqueous system in the presence of ionizing radiation and followed by modulation, if necessary, to an anhydrous system in the presence of radioactivity. If the experimental results appeared compatible with the model, further studies were envisioned to pursue more complex syntheses and polymerizations, to analyze extant samples of the model materials, and to investigate the primitive nature of organisms sur- viving in modern systems of the model. -2- EXPERIMENTAL I. Methods Irradiation Methods. High voltage electron irradiation was achieved with a Van de Graaf accelerator at the Western New York Nuclear Research Center, Buffalo, New York. The machine delivered 5 x 108 rads of 1.5 Mev electrons to samples within a few minutes. The dose rate was limited by the induced heating of the aqueous samples, so the irradiation period was generally set at 45 minutes to minimize temperature rise, The radiation dose was calculated from the beam current absorbed by the sample. The sample consisted of a 20 ml aqueous solution in a 75 mm diameter alumi- num dish covered with a thin aluminum foil to reduce evaporation losses. Mixing was provided by a teflon-covered magnetic stirrer, and temperature was controlled to 53-55OC by a thermostated water bath. Temperature was measured by an immersed iron-constantan thermocouple. For the irradiation of methane, a stainless steel capsule was used which contained 2.0 ml water at pH 8.5 with NaOH, and 6.0 cc free gas space. The gas phase used was 1 atmosphere of air plus 47 lbs. /sq. in. of methane. The solubility of methane in the aqueous phase under these condi- tions was not determined, but is 9 cc per 100 ml at 1 atm. Irradiation was performed at Radiation Applications, Inc. Long Island City, New York. The capsule was irradiated at ambient temperature with cobalt-60 gamma rays at 5 the rate of 1.43 x 10 rads per hour to the aqueous phase. The total absorbed 8 dose in this phase was 10 rads. Under these conditions the radiation ab- 6 sorbed by the gas phase of the system was about 1%, or 10 rads. The gas phase reactions of the methane with the water vapor and water fragments such as H*, OH', etc., therefore probably were much less significant than the aqueous solution reactions. However, the pure hydrocarbon products, repre- senting methane polymerizations, most probably were formed in the gas phase. The irradiated capsule was attached to a gas analysis vacuum line so that there was no possibility of loss of volatile products. -3-