The molecules necessary for life could have arisen during chemical reactions at the dawn of the development of the Earth.
4.5 billion years ago, when the Earth arose, it was a hot, lifeless ball. Today, different forms of life are found in abundance on it. In this regard, the question arises: what changes have taken place on our planet from the moment of its formation to the present day, and most importantly, how did the molecules that form living organisms arise on the lifeless Earth? In 1953, an experiment was carried out at the University of Chicago that has now become a classic. He pointed scientists way to answer this fundamental question.
In 1953, Harold Urey was already Nobel laureate, and Stanley Miller was just his graduate student. The idea of Miller's experiment was simple: in a basement laboratory he reproduced the atmosphere ancient earth, what it was like according to scientists, and watched from the side what was happening. With the support of Yuri, he assembled a simple apparatus from a glass spherical flask and tubes, in which the evaporated substances circulated in a closed circuit, cooled and re-entered the flask. Miller filled the flask with gases that Urey and Russian biochemist Alexander Oparin (1894–1980) believed were present in the atmosphere at the dawn of the Earth's formation - water vapor, hydrogen, methane and ammonia. To simulate solar heat, Miller heated the flask on a Bunsen burner, and to get an analogue of lightning flashes, he inserted two electrodes into a glass tube. According to his plan, the material, evaporating from the flask, was supposed to enter the tube and be exposed to an electric spark discharge. After this, the material had to cool and return to the flask, where the whole cycle began again.
After two weeks of operation of the system, the liquid in the flask began to acquire a dark red-brown hue. Miller analyzed this liquid and discovered amino acids in it - the basic structural units of proteins. This gave scientists the opportunity to study the origins of life from the point of view of basic chemical processes. Since 1953, sophisticated versions of the Miller-Urey experiment, as it has since become known, have produced all kinds of biological molecules - including complex proteins essential for cellular metabolism and fatty molecules called lipids that form cell membranes. Apparently, the same result could be obtained by using other energy sources instead of electrical discharges - for example, heat and ultraviolet radiation. So there is little doubt that all the components necessary for the assembly of a cell could have been obtained in chemical reactions that took place on Earth in ancient times.
The value of the Miller-Urey experiment is that it showed that lightning flashes in the atmosphere of the ancient Earth over several hundred million years could have caused the formation organic molecules, falling along with the rain into the “primary broth” (see also Theory of Evolution). Until now, unidentified chemical reactions occurring in this “broth” could lead to the formation of the first living cells. IN last years Serious questions arise about how these events unfolded, in particular the presence of ammonia in the atmosphere of the ancient Earth is called into question. In addition, several alternative scenarios have been proposed that could lead to the formation of the first cell, ranging from the enzymatic activity of the biochemical RNA molecule to simple chemical processes in the ocean depths. Some scientists even suggest that the origin of life has something to do with new science O
Volcanic emissions and lightning discharges are conditions for the spontaneous synthesis of various biological molecules. Photo of a volcanic eruption in Iceland from the site www.thunderbolts.info Followers of Stanley Miller, who conducted famous experiments in the 50s to simulate the synthesis of organic matter in the primary atmosphere of the Earth, again turned to the results of old experiments. They examined the materials remaining from those years using the latest methods. It turned out that in experiments that simulated volcanic emissions of a vapor-gas mixture, a wide range of amino acids and other organic compounds. Their diversity turned out to be greater than it was imagined in the 50s. This result focuses the attention of modern researchers on the conditions of synthesis and accumulation of primary high-molecular organics: synthesis could be activated in areas of eruptions, and volcanic ash and tuffs could become a reservoir of biological molecules. In May 1953, the journal Science published the results of a famous experiment on the synthesis of high molecular weight compounds from methane, ammonia and hydrogen under the influence of electrical discharges (see Stanley L. Miller. A Production of Amino Acids Under Possible Primitive Earth Conditions (PDF, 690 KB) // Science. 1953. V. 117. P. 528). The experimental setup was a system of flasks in which water vapor circulated. An electric discharge was generated in a large flask on tungsten electrodes. The experiment lasted a week, after which the water in the flask acquired a yellow-brown tint and became oily. Left: Stanley Miller's apparatus for experiments with electrical discharges in hot steam. Right: device diagram. Steam emissions through the nozzle should simulate steam-gas mixtures during volcanic eruptions. Images from the discussed articles in Science Miller analyzed the composition of organic matter using paper chromatography, a method then just becoming common among biologists and chemists. Miller discovered glycine, alanine and other amino acids in the solution. At the same time, similar experiments were carried out by Kenneth Alfred Wilde (see Kenneth A. Wilde, Bruno J. Zwolinski, Ransom B. Parlin. The Reaction Occurring in CO2–H2O Mixtures in a High-Frequency Electric Arc (PDF, 380 KB) // Science. 10 July 1953. V. 118. P. 43–44) with the difference that instead of a mixture of gases with reducing properties, the flask contained carbon dioxide - an oxidizing agent. Unlike Miller, Wild did not get any significant results. Miller and many scientists after him assumed a reducing rather than an oxidizing atmosphere at the beginning of the Earth's existence. The logical chain of their reasoning was as follows: we are in the position that life originated on Earth; for this we needed organic matter; they must have been the product of earthly synthesis; if synthesis occurs in a reducing atmosphere, but does not occur in an oxidizing atmosphere, then the primary atmosphere was reducing. In addition to the hypothesis of a reducing atmosphere on the early Earth, Miller’s experiments also prove the fundamental possibility of spontaneous synthesis of the necessary biological molecules from simple components. This hypothesis received serious support after the experiment of Juan Oro (Joan Oró; see J. Oró. Mechanism of Synthesis of Adenine from Hydrogen Cyanide under Possible Primitive Earth Conditions // Nature. 16 September 1961. V. 191. P. 1193–1194) , who in 1961 introduced hydrocyanic acid into Miller’s installation and obtained the nucleotide adenine, one of the four bases of DNA and RNA molecules. The possibility of spontaneous synthesis of high-molecular organic matter, including nucleotides and amino acids, became a powerful support for Oparin’s theory of the spontaneous generation of life in the primordial broth. An entire biological era has passed since these experiments. The attitude towards the theory of the primordial soup has become more wary. Over the past half century, scientists have been unable to come up with a mechanism for the selective synthesis of chiral molecules in inanimate nature and the inheritance of this mechanism in living organisms. The idea of a reducing atmosphere on the early Earth has also been strongly criticized. There has been no solution to the main question: how did a self-reproducing living creature emerge from non-living molecules? Arguments for the theory have appeared extraterrestrial origin life. However, in recent years, scientists have achieved tangible success in developing the theory of the origin of life from inorganic matter. The main achievements in this direction are, firstly, the discovery of the role of RNA in the development of bioorganic catalysis; The theory of the RNA world brings us closer to the answer to the question of how living systems were formed from nonliving organic matter. Secondly, the discovery of the catalytic functions of inorganic natural minerals in the reactions of high molecular weight organic synthesis, proof of the most important role of metal cations in the metabolism of living things. Thirdly, evidence of the selective synthesis of chiral isomers in natural terrestrial conditions (see, for example, “A new method for producing organic molecules has been discovered,” “Elements,” 10/06/2008). In other words, the theory of abiogenesis has received new justifications. From this perspective, the results of a re-examination of materials remaining from Miller’s old experiments, which were still stored, oddly enough, in sealed flasks in his laboratory, are interesting. In the 50s, Stanley Miller conducted three experiments that simulated various options conditions for the origin of life. The most famous of them, included in all school textbooks, is the formation of biomolecules when electrical discharges are passed through steam. The flask simulated the conditions for the evaporation of water over the ocean during thunderstorms. The second is the formation of biomolecules during weak ionization of gases - during the so-called silent discharge. It was a model of an ionized, steam-rich atmosphere early earth. In the third experiment, steam was supplied under high pressure, entering the flask in the form of powerful jets, through which electric discharges were passed, as in the first case. This event simulated volcanic emissions and the formation of hot volcanic aerosols. Biologists relied on the results of only the first, most successful experiment, because in the other two experiments little organic matter was synthesized and the variety of amino acids and other compounds was small. New results from the analysis of Miller's experiment with steam emissions. Amino acids not discovered by Miller are underlined. Amino acid designations are standard. Rice. from the discussed article in Science The Miller Volcanic Spark Discharge Experiment The re-study of these materials after Miller’s death in 2007 was undertaken by specialists from America and Mexico - from Indiana University (Bloomington), the Carnegie Institution (Washington), Research Department solar system Goddard Space Flight Center (Greenbelt), Scripps Institution of Oceanography (La Jolla, California), and Universidad Independant de Mexico (Mexico City). They had 11 flasks at their disposal, appropriately labeled by Miller. They all contained dried materials from the third experiment, the one that simulated volcanic emissions. The scientists diluted the precipitate with distilled water and analyzed the mixture, now using high-performance liquid chromatography and mass spectrometry. Modern methods revealed a high diversity of “biological” molecules. It turned out to be even higher than in the first experiment. Obviously, paper chromatography methods are less sensitive than liquid chromatography, so those compounds that were present in low concentrations have now been identified. The new results of the old experiment will apparently be taken into account by biochemists, microbiologists and volcanologists. Volcanic emissions are aerosols consisting of 96-98% water and containing ammonia, nitrogen, carbon monoxide, and methane. Volcanic emissions always contain high concentrations of metal compounds - iron, manganese, copper, zinc, nickel, etc., which participate in enzymatic reactions in living systems. Volcanic ashes and tuffs, as numerous experiments have shown, stimulate the growth of both anaerobic and aerobic microflora. Moreover, it is not even necessary to add various vital elements to the cultivation medium - the bacteria themselves will extract them from it. In ancient times, additional synthesis of organic matter could indirectly contribute to the growth of life on igneous substrates. In addition, aerosol chemistry is a poorly studied area, so the result of aerosol synthesis of high molecular weight biological molecules is all the more interesting. In this sense, chemists and volcanologists can make a significant contribution to the discussion of the problem of the origin of earthly life. The authors of the report note that the version of the reducing atmosphere of the early Earth is now in doubt. However, volcanic emissions and thunderstorms are a constant phenomenon on Earth, in ancient eras the intensity of both was presumably higher than in modern world. Therefore, whatever the atmosphere on the Archean and Proterozoic Earth, volcanic eruptions always create conditions for the synthesis of biological molecules. Sources: 1) Adam P. Johnson, H. James Cleaves, Jason P. Dworkin, Daniel P. Glavin, Antonio Lazcano, Jeffrey L. Bada. The Miller Volcanic Spark Discharge Experiment // Science. 17 October 2008. V. 322. P. 404. DOI: 10.1126/science.1161527. 2) Jeffrey L. Bada, Antonio Lazcano. Prebiotic Soup-Revisiting the Miller Experiment // Science. 2 May 2003. V. 300. P. 745–746. DOI: 10.1126/science.1085145. See also: V. N. Parmon. New in the theory of the emergence of life, “Chemistry and Life” No. 5, 2005. Elena Naimark
About why you may not like experiments, about the benefits of seminars, the nobility of a scientific supervisor and the emergence of a living thing in the background cold war We talk about it in our “History of Science” section.
Stanley Miller was born in 1930 into the family of a lawyer and a schoolteacher. Since childhood, the boy loved to read, studied well, loved nature, and went hiking with boy scouts. Following his brother, he entered the University of California, just like him, to study chemistry. Having easily passed the university course, he moved to the University of Chicago, which offered him a position as an assistant (after the death of his father, he could no longer afford to simply study). There began a long and difficult search for a topic for further work, a place where to apply my knowledge and bright mind.
Considering experiments to be “empty, time-consuming and not so important” (or maybe just expensive), Miller turned to theoretical problems. One of the professors whose work attracted Miller's attention was Edward Teller, who studied synthesis. chemical elements in the stars.
However, the Stanley Miller we are talking about today was “born” in the fall of 1951, when he began attending seminars with Professor Harold Urey, already a Nobel laureate at that time (for the discovery of deuterium). By that time, Yuri had become interested in cosmochemistry, the evolution of chemical elements in stars and planets, and made an assumption about the composition of the early atmosphere of the Earth. He believed that the synthesis of organic substances was possible in environments similar to ancient earth's atmosphere. These ideas fascinated Miller (so much so that he remembered the details of the lectures decades later), and he took his research to Urey.
Harold Urey
Wikimedia Commons
Thus, Miller took up a problem that attracted many scientists. William Harvey, Francesco Redi, Louis Pasteur, Lazzaro Spallanzani, Jacob Berzelius, Friedrich Wöhler argued about whether living things could arise from non-living things (and that’s not even everyone we’ve already written about in the History of Science).
The controversy did not subside in the 20th century. Here huge contribution contributed by our compatriot, Alexander Oparin. In the 1920s, he published an article “On the Origin of Life,” in which he outlined his theory of the origin of life from the “primordial soup.” Oparin suggested that the emergence of organic substances is possible in areas of increased concentration of high molecular weight compounds. When such zones acquired a shell that partially separated them from environment, they turned into coacervate drops - a key concept of the Oparin-Haldane theory (around the same time, similar ideas were developed by the British biologist John Haldane). Inside these droplets, simple organic substances can form, followed by complex compounds: proteins, amino acids. By absorbing substances from the external environment, droplets can grow and divide.
However, let's return to Miller. His enthusiasm and desire to arrange some kind of experiment and test the theory did not find Yuri's sympathy at first: a graduate student should not venture into the unknown, it is better if he does something simpler. In the end, the professor relented, but gave Miller a year. There will be no results, the topic will have to be changed.
Miller got to work: he took Urey's data on the composition of the early atmosphere and suggested that the synthesis of compounds necessary for the emergence of life could be stimulated by an electrical discharge (it is believed that lightning was not uncommon on Earth in ancient times). The setup consisted of two flasks connected by glass tubes. There was liquid in the lower flask, and a mixture of gases in the upper flask: methane, ammonia and hydrogen - and steam. Electrodes were also connected to the top flask, creating an electrical discharge. In different places this system was heated and cooled, and the substance circulated continuously.
Miller-Urey Experiment
Wikimedia Commons
A week later, the experiment was stopped and the flask with the cooled liquid was removed. Miller found that 10-15% of the carbon was converted to organic form. Using paper chromatography, he noticed traces of glycine (they appeared on the second day of the experiment), alpha and beta aminopropionic acid, aspartic and alpha aminobutyric acids.
Miller showed Urey these modest-sounding, but so significant results (they proved the possibility of the emergence of organic matter in the conditions of the early Earth), and the scientists, although not without problems, published them in the journal Science. Only Miller was listed as the author, otherwise, Yuri feared, all the attention would go to him, the Nobel laureate, and not to the real author of the discovery.
The molecules necessary for life could have arisen during chemical reactions at the dawn of the Earth's development.
4.5 billion years ago, when the Earth arose, it was a hot, lifeless ball. Today, different forms of life are found in abundance on it. In this regard, the question arises: what changes have taken place on our planet from the moment of its formation to the present day, and most importantly, how did the molecules that form living organisms arise on the lifeless Earth? In 1953, an experiment was carried out at the University of Chicago that has now become a classic. He showed scientists the way to answer this fundamental question.
In 1953, Harold Urey was already a Nobel laureate, and Stanley Miller was just his graduate student. The idea of Miller's experiment was simple: in a semi-basement laboratory, he reproduced the atmosphere of the ancient Earth, as scientists believed it was, and watched from the side what was happening. With the support of Yuri, he assembled a simple apparatus from a glass spherical flask and tubes, in which the evaporated substances circulated in a closed circuit, cooled and re-entered the flask. Miller filled the flask with gases that Urey and Russian biochemist Alexander Oparin (1894–1980) believed were present in the atmosphere at the dawn of the Earth's formation - water vapor, hydrogen, methane and ammonia. To simulate solar heat, Miller heated the flask on a Bunsen burner, and to get an analogue of lightning flashes, he inserted two electrodes into a glass tube. According to his plan, the material, evaporating from the flask, was supposed to enter the tube and be exposed to an electric spark discharge. After this, the material had to cool and return to the flask, where the whole cycle began again.
After two weeks of operation of the system, the liquid in the flask began to acquire a dark red-brown hue. Miller analyzed this liquid and discovered amino acids in it - the basic structural units of proteins. This gave scientists the opportunity to study the origins of life from the point of view of basic chemical processes. Since 1953, sophisticated versions of the Miller-Urey experiment, as it has since become known, have produced all kinds of biological molecules - including complex proteins essential for cellular metabolism and fatty molecules called lipids that form cell membranes. Apparently, the same result could be obtained by using other energy sources instead of electrical discharges - for example, heat and ultraviolet radiation. So there is little doubt that all the components necessary to assemble a cell could have been obtained in chemical reactions that took place on Earth in ancient times.
The value of the Miller-Urey experiment is that it showed that lightning flashes in the atmosphere of the ancient Earth over several hundred million years could have caused the formation of organic molecules that fell with rain into the “primordial soup” ( see also Evolution theory). Until now, unidentified chemical reactions occurring in this “broth” could lead to the formation of the first living cells. In recent years, serious questions have arisen about how these events unfolded, in particular the presence of ammonia in the atmosphere of the ancient Earth has been questioned. In addition, several alternative scenarios have been proposed that could lead to the formation of the first cell, ranging from the enzymatic activity of the biochemical RNA molecule to simple chemical processes in the ocean depths. Some scientists even suggest that the origin of life has to do with the new science of complex adaptive systems and that it is possible that life is an unexpected property of matter that appears abruptly at a certain moment and is absent from it. components. Nowadays, this area of knowledge is experiencing a period of rapid development, various hypotheses appear and are tested in it. From this whirlpool of hypotheses should emerge a theory about how our most distant ancestors arose.
See also:
1953 |
Stanley Lloyd Miller, b. 1930
American chemist. Born in Oakland, California, he was educated at the University of California at Berkeley and the University of Chicago. Since 1960 professional activity Miller was primarily associated with the University of California, San Diego, where he served as a professor of chemistry. For his work on the Miller-Urey experiment, he was awarded the title of research fellow at the California Institute of Technology.
Harold Clayton Urey, 1893-1981
American chemist. Born in Walkerton, Indiana, the son of a minister. He studied zoology at Montana State University and received a PhD in chemistry from the University of California, Berkeley. He was the first to apply physical methods in chemistry and in 1934 was awarded Nobel Prize in chemistry for the discovery of deuterium, a heavy isotope of hydrogen. Later, his activities were mainly related to the study of differences in the rates of chemical reactions when using different isotopes.
ATTENTION!!! THIS MATERIAL HAS BEEN REVISED, ADDED AND INCLUDED IN THE BOOK “Creation or Evolution? How old is the Earth? TO READ GO TO PAGE -->
In the middle of the last century, University of Chicago scientist Stanley Miller tried in the laboratory to recreate the broth that, in his opinion, was on Earth before the origin of life on it. He mixed water vapor, ammonia, and methane in a flask and passed electricity through this medium. As a result, 3 types of amino acids were obtained out of 20, which are the constituent elements of protein (protein) of a living organism. Thus, the fact of the random origin of life was allegedly proven experimentally. However, this experiment has several significant drawbacks, which, although not advertised, are recognized by the supporters of evolution themselves: 1. ammonia could not have been on Earth in such quantities, since this gas is destroyed under the influence of ultraviolet rays from the sun; 2. methane was not found in ancient sedimentary alumina; 3. The scientist immediately isolated the amino acids obtained during the experiment from further exposure to electrical discharges, since he knew that the current would again break the bonds obtained. But in nature, the thunderstorms that supposedly contributed to the creation of amino acids did not stop, which means they would always immediately destroy what they created; 4. The resulting amino acids, even theoretically, could not form any life, since as a result of the experiment, amino acids with a left and a right helix were obtained. But protein consists of a complex chain of left-handed amino acids, which are difficult to combine into one whole, but are easily broken. The presence of at least one amino acid with a right-handed helix destroys everything created previously; 5. oxygen was not taken into account, although today geologists find oxidized stones at great depths, which proves the constant presence of oxygen in the earth’s atmosphere. The oxygen present in that atmosphere would destroy the elements of the substance that the scientist received. Thus, the primary atmosphere in Miller's experiment was fictitious. After for long years silence, Miller himself admitted that the environment he used in his experience was not real. Why did Miller insist on this gas mixture at one time? The answer is simple: without ammonia, amino acid synthesis is impossible.
Radiocarbon dating is wrong
The Earth's magnetic field is weakening
"Punctured" layers
Soil erosion at the initial level
The Moon is less than 10,000 years old
Population growth corresponds to the Biblical age of the earth
Moon close to Earth
Ice rings do not show years
The coral reef grew for less than 5,000 years
Dinosaurs are reliable witnesses
All people come from one pair
Civilizations and writing are less than 5,000 years old
The layers of the Earth do not have their own dating. Geological layers. Geochronological scale
Lack of scientific evidence. Kent Hovind
