Miller Urey Experiment

9 Key excerpts on "Miller Urey Experiment"

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  The Little Book of Aliens

  • Adam Frank(Author)
  • 2023(Publication Date)
  • Harper

    (Publisher)

  In 1953, two chemists at the University of Chicago, Stanley Miller and Harold Urey, created a simulated version of the early Earth in a test tube. They took simple molecules like methane, ammonia, hydrogen, and water and stuck them in a jar. This mixture was supposed to mimic Earth’s early atmosphere. Then they added energy in the form of an electrical current. This was their laboratory version of lightning, something that could be expected in any atmosphere. Finally, they let the results collect at the bottom of a beaker, their version of a pond of water lying somewhere on the young planet.

  After running this experiment for a week, Miller and Urey found that a “brown goo” had collected in their mock pond. Chemical analysis showed that the goo was a rich soup of prebiotic molecules like glycine, lactic acid, and urea. All of them were important molecules that life uses quite a lot of. Most important of all, though, a substantial fraction of the molecules floating in the brown goo were amino acids. The basic stuff of life’s proteins were just sitting there in the bottom of the flask. It almost seemed that all the scientists had to do was just wait a bit longer and an amoeba would have crawled out of the beaker. The ancient problem of how life started seemed a step or two away from being solved!

  The Miller-Urey experiment was a major breakthrough, a major surprise, and an instant classic of biochemistry. For lots of scientists, it was proof that you could start with nonliving material and the natural processes of physics and chemistry would eventually serve up the molecular basis of life. Many were ready to claim victory.

  It turned out to be a little more complicated. OK, more than a little. Later studies made it clear that the early Earth would not have had an atmosphere like the one that Miller and Urey had assumed. Later, scientists realized that other environments might serve as better starting points for life than warm ponds with a primordial soup of prebiotic molecules. Some researchers, for example, focused on volcanic vents deep in the ocean, where molten rock comes in contact with sea water, creating a stew of chemicals just right for getting biology going. The hot water is important too, because heated molecules collide with each other faster and more often than chilly ones. The more random collisions, the faster the whole process works.

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  Beyond The Stars: Our Origins And The Search For Life In The Universe

  Our Origins and the Search for Life in The Universe

  • Paolo Saraceno, David L Goodstein(Authors)
  • 2012(Publication Date)
  • World Scientific

    (Publisher)

  Miller and Urey ’s experiment is shown schematically in Figure 5.1. On the left are the molecules they put into the container to emulate the primordial atmosphere; below, the amino acids produced by subjecting the gas to electri-cal discharges are shown. The news of the experiment rapidly spread around the world and raised a great clamor, particularly because radio astronomers had not yet discovered amino acids in interstellar space. For some time, people were convinced that Oparin’s theory had been proven to be correct and that the origin of life on the Earth had been explained. CH 4 Methane Ammonia Hydrogen Carbon Monoxide Carbon Dioxide Water Triptophan Phenylanine Glycine Histidine Valine Molecules of the primordial atmosphere 60,000 volt Amino acids Protein NH 3 CO CO 2 H 2 H 2 O Figure 5.1: The Miller–Urey experiment. At the top-left corner the primordial Earth’s simple molecules are shown. At the bottom center there are the amino acids produced by the experiment. On the right-hand side a protein molecule is shown, in which every point is an atom. 112 Beyond the Stars Many laboratories carried out every possible variation of the experiment. They found the process to be very efficient and many different amino acids should have been produced in the ancient atmosphere. Because there was no oxygen to oxidize the amino acids, nor were there any biological species to eat them, scientists concluded that they must have been produced to excess, filling the planet’s oceans. The density of amino acids would have given the seas the consistency of a chicken soup; this is the origin of the name primordial soup , which is still used to denote any mixture from which life might emerge. After the initial experiments, the “soup” was stimulated in every possible way in the hope that the amino acids would evolve into something more complex. This did not happen and with the time passing the initial enthusiasm died down.

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  Astrobiology

  An Introduction

  • Alan Longstaff(Author)
  • 2014(Publication Date)
  • CRC Press

    (Publisher)

  (Photo credit: Paul Harrison, Reading, UK.) 215 Origin of Life 8.2.1.1 Urey–Miller Experiments Have a Fatal Flaw In some of the most famous scientific experiments ever done, Harold Urey and Stanley Miller in 1952 set out to synthesize organic molecules from gases assumed to be pres-ent on early Earth. This was to be the first step in the genesis of life. The assumption at the time was that life had emerged from a primeval soup, rather as Darwin had surmised in a letter to botanist Joseph Hooker in 1871: “we could con-ceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc., present, that a protein compound was chemically formed ready to undergo still more complex changes.” Using the spectroscopically determined composition of Jupiter’s atmosphere as a proxy for what the early Earth would have captured from the solar nebula, it was reckoned that the major gases in the Earth’s early atmosphere were water (H 2 O), methane (CH 4 ), ammonia (NH 3 ), and hydrogen (H 2 ). Accordingly, the original Urey–Miller experiment mixed these gases in a flask, passing high voltage sparks through it to simulate lightning that provided the energy for chemical reactions. After a week, more than 10% of the carbon was in the form of BOX 8.3 SECONDARY ION MASS SPECTROMETRY (SIMS) Secondary ion mass spectrometry (SIMS) is an ion microprobe technology that allows qualitative mapping of the distribution of elements in a sample. NanoSIMS is a high resolution version. It can be made quantitative by the use of calibration standards. A primary ion beam (Cs + or O − ) is scanned across the surface of the sample, and the sputtered ions are extracted to a mass spectrometer which determines their mass/charge ratio. With the Cs + primary beam negatively charged secondary ions can be detected, and with the O − primary beam, positively charged secondary ions can be detected.

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  Prebiotic Photochemistry

  From UreyMiller-like Experiments to Recent Findings

  • Franz Saija, Giuseppe Cassone, Franz Saija, Giuseppe Cassone(Authors)
  • 2021(Publication Date)
  • Royal Society of Chemistry

    (Publisher)

  40 . This limitation still stands to this day and explains why most of the dozens experiments that followed to simulate early Earth photochemistry used a plasma setup and not a UV lamp.

  After passing through the discharge, the gas phase containing the original reactive and the newly-formed products would interact with liquid water. This design induced an accumulation of compounds produced in the discharge into the water phase. Meanwhile NH3 , CH4 , H2 O and H2 , which were more volatile, were able to recirculate through the system.

  Miller published a very succinct report on his experiment in 1953 where he stated that after continuously running the experiment for a week, the water went from transparent to pink to end up forming a dark and turbid red solution by the end of the week. This colour was due to complex organic molecules adsorbed on the silica. He also noted the presence of insoluble organic material. Chromatographic analyses revealed the formation of amino acids, in particular Glycine and α- and β-alanine (See Figure 4.2 in Miller (1953)).

  Figure 4.2 Picture of the setup used by Fleury et al. to investigate ionosphere formation of organic aerosols in the early Earth. This setup is an example of the small dozen modern setups currently operating for these types of laboratory investigations. With permission of LATMOS-UVSQ.

  In Miller and Urey's (1959) paper,41 they stated further analysis of the products of the 1953 experiments. Re-analysis using modern technology was also carried out in 2008 and 2011 on unopened vials including a previously unreported simulation including sulphur compounds.

  42 ,43

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  An Introduction to Astrobiology

  • David A. Rothery, Iain Gilmour, Mark A. Sephton(Authors)
  • 2018(Publication Date)
  • Cambridge University Press

    (Publisher)

  It now seems that the more stable molecules – carbon dioxide, nitrogen and water – dominated the Earth’s early atmosphere. Under these less reducing conditions Miller−Urey synthesis is much more difficult. So it appears that the environment of the early Earth might have been fit for sustaining life but less suitable for the in situ production of life’s organic raw materials. 1 ORIGIN OF LIFE 23 Table 1.5 Abundances of amino acids synthesized in the Miller−Urey experiment and those found in the Murchison meteorite. The number of dots represents relative abundance, which in most cases matches well between the products of the Miller-Urey experiment and the Murchison meteorite. Those amino acids used by life (i.e. in proteins) are indicated. Amino acid Abundance of amino acid Found in proteins on Earth Synthesized in the Miller−Urey experiment Found in the Murchison meteorite glycine •••• •••• yes alanine •••• •••• yes α-amino-N-butyric acid ••• •••• no α-aminoisobutyric acid •••• •• no valine ••• •• yes norvaline ••• ••• no isovaline •• •• no proline ••• • yes pipecolic acid • • no aspartic acid ••• ••• yes glutamic acid ••• ••• yes β-alanine •• •• no β-amino-N-butyric acid •• •• no β-aminoisobutyric acid • • no γ-aminobutyric acid • •• no sarcosine •• ••• no N-ethylglycine •• •• no N-methylalanine •• •• no 1.5.4 Cometary organics Further confirmation that at least some of the building blocks of life can form in space comes from analysis of samples from comets. Dust samples collected during a fly-by of comet Wild-2 and brought to Earth by NASA’s Stardust mission in 2006 were found to contain glycine (the only amino acid whose formation does not probably require the presence of liquid water).

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  Evolution

  The First Four Billion Years

  • Michael Ruse, Joseph Travis, Michael Ruse, Joseph Travis(Authors)
  • 2011(Publication Date)
  • Belknap Press

    (Publisher)

  Miller achieved his results by means of an apparatus in which he could simulate the interaction between an atmosphere and an ocean (see Figure 1). As an energy source Miller chose a spark discharge, considered to be the second-largest energy source, in the form of lightning and coronal discharges, The Origin of Life 55 Figure 1. The apparatus used in the 1953 Miller experiment. The 500 cc flask was used to represent the oceans and the 5-liter flask was used to represent the atmosphere. A spark discharge generated across the electrodes with a Tesla coil, invented by Nikola Tesla in 1891, was used to mimic lightning and corona discharges in the atmosphere. on the early earth after UV radiation (Miller and Urey 1959). The apparatus was filled with various mixtures of methane, ammonia, and hydrogen, as well as water, which was then heated during the experiment. A spark dis-charge between the tungsten electrodes, which simulated lightning and co-rona discharges in the early atmosphere, was produced using a high-frequency Tesla coil with a voltage of 60,000 V. The reaction time was usually a week or so, and the maximum pressure was 1.5 bars. With this experimental setup, Miller was able to transform almost 50% of the original carbon (in the form of methane) into organic compounds. Although most of the synthesized or-ganic material was an insoluble tarlike solid, he was able to isolate amino acids and other simple organic compounds from the reaction mixture. Glycine, the simplest amino acid, was produced in 2% yield (based on the original amount of methane carbon), whereas alanine, the simplest amino acid with a chiral center, showed a yield of 1%. Miller was able to demon-strate that the alanine that was produced was a racemic mixture (equal amounts of D- and L-alanine). This provided convincing evidence that the amino acids were produced in the experiment and were not biological con-taminants somehow introduced into the apparatus.

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  Origins of the Earth, Moon, and Life

  An Interdisciplinary Approach

  • Akio Makishima(Author)
  • 2017(Publication Date)
  • Elsevier

    (Publisher)

  9.2.2. The Miller Experiment (or the Miller-Urey Experiment)

  To prove the Oparin–Haldane hypothesis, S. Miller conducted the famous Miller experiment (or Miller-Urey experiment) under the supervision of H. Urey in 1952 (Miller, 1953 ). In Fig. 9.1 , the apparatus which Miller used is indicated.

  Two flasks were connected with two pipes. One flask with pure water was heated to boiling to make water vapor. The water vapor was led through one pipe to another reaction flask containing methane, ammonia, and hydrogen gases, in which electrical sparks were supplied. The water vapor was cooled by a condenser, and the liquid water was returned to the boiling flask through another pipe.

  Figure 9.1  The Miller experiment.

  The water in the flask became pink, and deep red after a week. Most turbidity was due to colloidal silica from the glass (they do not seem to have used a “silica glass flask” but a “soda glass flask”). At the end of the run, the boiling flask was removed and HgCl2 was added to prevent the growth of living organisms. Then the sample solution was combined with Ba(OH)2 and evaporated in vacuum by adding H2 SO4 , and then neutralized with Ba(OH)2 , filtered, and concentrated in vacuum. The paper chromatogram showed glycine, α-alanine, β-alanine, aspartic acid, and unidentified organic compounds.

  Although the synthesized amino acids were racemic, it was proved that some amino acids (CHONs) can be synthesized by such a simple condition.

  9.3. Cosmic Origin of CHOs and CHONs

  9.3.1. CHOs and CHONs in Carbonaceous Chondrites and Comets

  In a collision between pure ice comets, no organic materials are formed because the impacters are composed only of ice (water). However, various amino acids and nucleobases (CHONs) are found in carbonaceous chondrites (Kvenvolden et al., 1970 ; Cronin and Moore, 1971 ; Stoks and Schwartz, 1979 , 1981 ; Martins et al., 2008 ; Callahan et al., 2011 ). In addition, amino acid and precursors (ammonia, methanol, and carbonyl compounds, which correspond to CHOs) were observed in actual carbonaceous chondrites (Crovisier and Bockelée-Morvan, 1999 ; Bockeléee-Morvan et al., 2000 ; Ehrenfreund and Charnley, 2000 ; Ehrenfreund et al., 2002 ; Mumma et al., 2003 ; Festou et al., 2005 ; DiSanti et al., 2013

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  A Chaos of Delight

  Science, Religion and Myth and the Shaping of Western Thought

  • Geoffrey Dobson(Author)
  • 2016(Publication Date)
  • Routledge

    (Publisher)

  100

  The Urey and Miller experiment was modified nearly ten years later by Juan Oró, who synthesized all the 20 amino acids that exist in living systems.101 Further, Oró found that if hydrogen cyanide (HCN) was bubbled into the “primordial” soup, trace amounts of the purine adenine could be synthesized.102 This was an important discovery because adenine is one of the two purines that are the building-blocks of our information-laden genetic library in DNA and RNA and passed on from generation to generation.103 Adenine is also a vital component of the energy currency of life, known as ATP (adenosine-5′-triphosphate), and it is not inconceivable that if phosphate and other precursors were added to the mixture a number of nucleosides and nucleotides could be synthesized.

  In 1985, Sidney Fox and colleagues made another important discovery They synthesized another essential feature of a cell: its membrane.104 By heating and drying a mixture of amino acids and re-dissolving them with other molecules, small stable spheres were formed.105 While synthesizing life’s building-blocks or a synthetic membrane in the laboratory is a far cry from solving the mystery of life’s origins 3.8–4 bya, they are important first steps demonstrating the natural tendency of atoms to associate and support the idea of chemical evolution as one explanation for the origin of life. Among the shortfalls of the Urey–Miller-type experiments are the low yield of material, a lack of specificity of the reactions and lack of informational transfer to build longer polymers necessary for life.

  The first replicators: information and action

  To go from a bacterium to people is less of a step than to go from a mixture of amino acids to a bacterium.

  Margulis106

  Biological information is stored in the DNA of the genes,107 which in eukaryotes are located on chromosomes in the nucleus of a cell. Each chromosome contains a different molecule of DNA , and human beings have 46 chromosomes in every cell (except sperm and egg cells and mature red blood cells). The DNA molecule looks like a twisted rope ladder, a double helix; this was discovered by James Watson, Francis Crick and Rosalind Franklin in 1953.108 All the DNA contained in the cells of an organism including its genes is called a genome. The human genome contains around 32 000 genes, and only about 1 per cent of the code for proteins that make up the living organism (see Ch. 11 ). If you could unwind the entire length of DNA in each cell (connect all 46 chromosomes end to end), it would be approximately 2 m long. And if all the DNA in the 1014

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  Genesis and Evolutionary Development of Life

  • A. I. Oparin(Author)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  This was greatly aided by the work of several astronomers, physicists, chemists, and geologists. In this connection, one must note Urey's book Planets, their Origin and Development (86) and Bernal's Physical Basis of Life (87). Solution of the problem of the further evolution of the primary hydrocarbon compounds on our planet, their transformations under the *In J. Bernal's book The Origin of Life published in 1967 a complete English translation of this book is given as an appendix. 1. SHORT HISTORY 35 conditions of the ancient hydrosphere and atmosphere of Earth were greatly aided by numerous experiments reproducing these conditions in a laboratory environment. These experiments were successfully begun by the ^American scientist Miller (88) who obtained amino acids - those most important components of the protein molecule — by subjecting a gas mixture consisting of methane, ammonia, hydrogen, and water vapor to electric discharges. Analogous syntheses of amino acids were carried out by Pavlovskaya and Pasynskii (89) by the action of ultraviolet light. Subsequently, similar investigations were carried out by numerous scientists in several countries of the world. We will describe these investigations in further accounts. Here it is only necessary to note that a large number of differing substances, as well as their polymers, anal-ogous to proteins, nucleic acids, etc. were synthesized from primitive hydrocarbon compounds. In addition to this, a broad investigation was made of the primary formation from these polymers of multi-molecular formations, the emergence of primitive metabolism in them, etc. In the middle of our century a decisive crisis in the relationship of naturalists to the problem of the origin of life has occurred. Earlier this problem was, if it can be thus expressed, prohibited; the scientific literature devoted to it at that time was extremely scanty and in most cases was only general and speculative in character.

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