About why you can not like experiments, about the benefits of seminars, the nobility of a scientific leader and the emergence of the living against the backdrop of the Cold War, we tell in our section “History of Science”.
Stanley Miller was born in 1930 to a lawyer and school teacher. From childhood, the boy loved to read, studied well, loved nature, went on hikes 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 their knowledge and bright mind.
Considering experimentation to be “empty, time-consuming and not very important” (or maybe just costly), Miller turned to theoretical problems. One of the professors whose work caught Miller's attention was Edward Teller, who studied the synthesis of chemical elements in stars.
However, the Stanley Miller we are talking about today was "born" in the fall of 1951, when he began attending the seminars of Professor Harold Urey, already at that time a Nobel laureate (for the discovery of deuterium). Urey by that time was carried away by 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 is possible in environments similar to the ancient earth's atmosphere. These ideas fascinated Miller (so much so that he remembered the details of the lectures decades later), and he moved on with his research to Urey.
Harold Urey
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Thus, Miller tackled a problem that attracted many scientists. William Harvey, Francesco Redi, Louis Pasteur, Lazzaro Spallanzani, Jakob Berzelius, Friedrich Wöhler argued about whether living things can arise from non-living things (and this is not even all that we have already written about in the History of Science).
The controversy did not subside even in the 20th century. Here our compatriot Alexander Oparin made a great contribution. In the 1920s, he published an article "On the Origin of Life", in which he outlined his theory of the origin of living things from the "primordial soup". Oparin suggested that the occurrence of organic substances is possible in areas of high concentrations of macromolecular compounds. When such zones acquired a shell that partially separated them from the environment, they turned into coacervate drops - the key concept of the Oparin-Haldane theory (at about the same time, similar ideas were developed by the British biologist John Haldane). Inside these drops, simple organic substances can be formed, followed by complex compounds: proteins, amino acids. By absorbing substances from the environment, droplets can grow and divide.
But back to Miller. At first, his enthusiasm and desire to arrange some kind of experiment and test the theory did not find sympathy with Yuri at first: a graduate student should not climb 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 subject will have to be changed.
Miller set to work: he took Urey's data on the composition of the early atmosphere and suggested that the synthesis of the compounds necessary for the emergence of life could be stimulated by an electric discharge (it is believed that lightning was not uncommon on Earth even in antiquity). The setup consisted of two flasks connected by glass tubes. In the lower flask there was a liquid, in the upper - a mixture of gases: methane, ammonia and hydrogen - and steam. Electrodes were also connected to the upper flask, creating an electrical discharge. In different places, this system was heated and cooled, and the substance circulated continuously.
Miller Experiment - Urey
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After a week, the experiment was stopped and the flask with the cooled liquid was taken out. Miller found that 10-15% of the carbon had gone into organic form. Using paper chromatography, he noticed traces of glycine (they appeared already 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 meaningful results (they proved the possibility of the appearance of organics in the conditions of the early Earth), and scientists, although not without problems, published them in the journal Science. Only Miller was listed among the authors, otherwise, Yuuri feared, all the attention would go to him, the Nobel laureate, and not to the real author of the discovery.
MOSCOW, January 21 - RIA Novosti. American biologists have successfully replicated one of the most famous experiments of the mid-20th century, the so-called Miller-Urey experiment, and successfully recreated a set of several primary amino acids from the simplest inorganic compounds during a long chemical evolution, according to an article published in the journal JoVE.
Conditions on planets in the early universe were suitable for the origin of lifeThe temperature of the cosmic microwave background 15 million years after the Big Bang was up to 30 degrees Celsius, due to which the planets, if they existed at that time, could have liquid water necessary for life.Eric Parker from the Georgia Institute of Technology in Atlanta (USA) and his colleagues tried to repeat one of the key stages in the chemical evolution of organics on Earth, following in the footsteps of two famous biochemists of the world - Stanley Miller and Harold Urey.
In the mid-1950s, Miller and Urey experimentally tested and confirmed the truth of the abiogenetic hypothesis of the origin of life, the foundations of which were formulated by the Russian biologist Alexander Oparin in 1922.
Miller and Urey tried to create amino acids from simple compounds such as water, ammonia, carbon monoxide and methane, recreating the conditions that prevailed on the early Earth. To do this, they heated the "primary broth" with these substances and passed the steam through a flask into which electrodes were inserted, and then cooled it. After some time, amino acids began to appear in this "syrup".
In subsequent years, scientists repeatedly repeated the Miller-Urey experiment, but the procedures they used were too complex and confusing to fully verify their results. The authors of the article studied the description of Miller and Urey's experiment, simplified it and prepared a video explaining how to conduct the experiment.
“Our results show that amino acids, the building blocks of life, can form under the conditions that prevailed on the early Earth. Miller did not call for repeating this experiment for the reason that his experimental setup could explode. If you read the description of his methodology, then it will not be entirely clear how the experiment was carried out. Therefore, we have prepared a safe methodology for conducting the experiment for interested colleagues, "concludes Parker.
Scheme of the experiment.
Miller Experiment - Urey- a famous classical experiment in which hypothetical conditions of the early period of the Earth's development were simulated to test the possibility of chemical evolution. In fact, it was an experimental test of the hypothesis, previously expressed by Alexander Oparin and John Haldane, that the conditions that existed on the primitive Earth favored chemical reactions that could lead to the synthesis of organic molecules from inorganic ones. Conducted in 1953 by Stanley Miller and Harold Urey. The apparatus designed for the experiment included a mixture of gases corresponding to the then ideas about the composition of the atmosphere of the early Earth, and electrical discharges passed through it.
The Miller-Urey experiment is considered one of the most important experiments in the study of the origin of life on Earth. Primary analysis showed the presence of 5 amino acids in the final mixture. However, a more accurate reanalysis published in 2008 showed that the experiment resulted in the formation of 22 amino acids.
Description of the experiment
The assembled apparatus consisted of two flasks connected by glass tubes in a cycle. The gas filling the system was a mixture of methane (CH 4), ammonia (NH 3), hydrogen (H 2) and carbon monoxide (CO). One flask was half-filled with water, which evaporated when heated and the water vapor fell into the upper flask, where electrical discharges were applied using electrodes, imitating lightning discharges on the early Earth. Through a cooled tube, the condensed vapor returned to the lower flask, providing constant circulation.
After one week of continuous cycling, Miller and Urey found that 10-15% of the carbon had gone into organic form. About 2% of the carbon turned out to be in the form of amino acids, with glycine being the most abundant of these. Sugars, lipids, and nucleic acid precursors have also been found. The experiment was repeated several times in 1953-1954. Miller used two versions of the apparatus, one of which, the so-called. "volcanic", had a certain constriction in the tube, which led to an accelerated flow of water vapor through the discharge flask, which, in his opinion, better simulated volcanic activity. Interestingly, a reanalysis of Miller's samples, conducted 50 years later by the professor and his former collaborator Jeffrey Bade (eng. Jeffrey L. Bada) using modern research methods, found 22 amino acids in samples from the “volcanic” apparatus, that is, much more than previously thought.
Miller and Urey based their experiments on ideas from the 1950s about the possible composition of the Earth's atmosphere. After their experiments, many researchers conducted similar experiments in various modifications. It was shown that even small changes in the process conditions and the composition of the gas mixture (for example, the addition of nitrogen or oxygen) could lead to very significant changes in both the resulting organic molecules and the efficiency of the process of their synthesis. At present, the question of the possible composition of the Earth's primary atmosphere remains open. However, it is believed that the high volcanic activity of that time also contributed to the release of such components as carbon dioxide (CO 2), nitrogen, hydrogen sulfide (H 2 S), sulfur dioxide (SO 2).
Criticism of the conclusions of the experiment
The conclusions about the possibility of chemical evolution, made on the basis of this experiment, are criticized. The main argument of critics is the lack of a single chirality in the synthesized amino acids. Indeed, the resulting amino acids were an almost equal mixture of stereoisomers, while for amino acids of biological origin, including those that are part of proteins, the predominance of one of the stereoisomers is very characteristic. For this reason, the further synthesis of complex organic substances underlying life directly from the resulting mixture is difficult. According to critics, although the synthesis of the most important organic substances has been clearly demonstrated, the far-reaching conclusion about the possibility of chemical evolution, drawn directly from this experience, is not fully justified.
see also
Notes
Literature
- MILLER S.L. (May 1953). "A production of amino acids under possible primitive earth conditions". Science (New York, N.Y.) 117 (3046): 528–9. PMID 13056598 .
- MILLER SL, UREY HC (July 1959). "Organic compound synthesis on the primitive earth". Science (New York, N.Y.) 130 (3370): 245–51. PMID 13668555 .
- Lazcano A, Bada JL (June 2003). "
The Miller-Urey experiment is a famous classic experiment that simulated hypothetical conditions in the early Earth to test the possibility of chemical evolution. Conducted in 1953 by Stanley Miller and Harold Urey. The apparatus designed for the experiment included a mixture of gases corresponding to the then ideas about the composition of the atmosphere of the early Earth, and electrical discharges passed through it.
The Miller-Urey experiment is considered one of the most important experiments in the study of the origin of life on Earth. Primary analysis showed the presence of 5 amino acids in the final mixture. However, a more accurate reanalysis published in 2008 showed that the experiment resulted in the formation of 22 amino acids.
Description of the experiment
The assembled apparatus consisted of two flasks connected by glass tubes in a cycle. The gas filling the system was a mixture of methane (CH 4), ammonia (NH 3), hydrogen (H 2) and carbon monoxide (CO). One flask was half-filled with water, which evaporated when heated and the water vapor fell into the upper flask, where electrical discharges were applied using electrodes, imitating lightning discharges on the early Earth. Through a cooled tube, the condensed vapor returned to the lower flask, providing constant circulation.
After one week of continuous cycling, Miller and Urey found that 10-15% of the carbon had gone into organic form. About 2% of the carbon turned out to be in the form of amino acids, with glycine being the most abundant of these. Sugars, lipids and nucleic acid precursors have also been found. The experiment was repeated several times in 1953-1954. Miller used two versions of the apparatus, one of which, the so-called. "volcanic", had a certain constriction in the tube, which led to an accelerated flow of water vapor through the discharge flask, which, in his opinion, better simulated volcanic activity. Interestingly, a reanalysis of Miller's samples, conducted 50 years later by Professor and his former collaborator Jeffrey L. Bada, using modern research methods, found 22 amino acids in samples from the "volcanic" apparatus, that is, much more than was considered earlier.
Miller and Urey based their experiments on ideas from the 1950s about the possible composition of the Earth's atmosphere. After their experiments, many researchers conducted similar experiments in various modifications. It was shown that even small changes in the process conditions and the composition of the gas mixture (for example, the addition of nitrogen or oxygen) could lead to very significant changes in both the resulting organic molecules and the efficiency of the process of their synthesis. At present, the question of the possible composition of the Earth's primary atmosphere remains open. However, it is believed that the high volcanic activity of that time also contributed to the release of such components as carbon dioxide (CO 2), nitrogen, hydrogen sulfide (H 2 S), sulfur dioxide (SO 2).
Criticism of the conclusions of the experiment
The conclusions about the possibility of chemical evolution, made on the basis of this experiment, are criticized.
As it becomes clear, one of the main arguments of critics is the lack of a single chirality in the synthesized amino acids. Indeed, the amino acids obtained were an almost equal mixture of stereoisomers, while for amino acids of biological origin, including those that are part of proteins, the predominance of one of the stereoisomers is quite typical. For this reason, the further synthesis of complex organic substances underlying life directly from the resulting mixture is difficult. According to critics, although the synthesis of the most important organic substances has been clearly demonstrated, the far-reaching conclusion about the possibility of chemical evolution, drawn directly from this experience, is not fully justified.
Much later, in 2001, Alan Saghatelyan showed that self-replicating peptide systems were able to effectively amplify molecules of a certain rotation in a racemic mixture, thus showing that the predominance of one of the stereoisomers could arise naturally. In addition, it has been shown that there is a possibility of spontaneous occurrence of chirality in conventional chemical reactions, and there are also known ways to synthesize a number of stereoisomers, including hydrocarbons and amino acids, in the presence of optically active catalysts. However, nothing of the kind explicitly happened directly in this experiment.
They try to solve the problem of chirality in other ways, in particular, through the theory of introduction of organic matter by meteorites.
Biochemist Robert Shapiro pointed out that the amino acids synthesized by Miller and Urey are much less complex molecules than nucleotides. The simplest of those 20 amino acids that are part of natural proteins has only two carbon atoms, and 17 amino acids from the same set have six or more. Amino acids and other molecules synthesized by Miller and Urey contained no more than three carbon atoms. And nucleotides in the process of such experiments were never formed at all.
summary of other presentations"Biochemical evolution of Oparin" - 2) Formation in the primary reservoirs of the Earth from the accumulated organic compounds of biopolymers, lipids, hydrocarbons. The essence of the hypothesis boiled down to the following... The origin of life on Earth is a long evolutionary process of the formation of living matter in the depths of inanimate matter. 1) Synthesis of initial organic compounds from inorganic substances in the conditions of the primary atmosphere of the primitive Earth. Oparin's theory. 1894-1980.
"The Oparin Hypothesis" - Biography. The hypothesis of spontaneous origin of life. The hypothesis of biochemical evolution. Hypothesis of the origin of life on Earth AI Oparina. Clots called coacervate drops. Biography of A.I. Oparin. English biologist. Alexander Ivanovich Oparin. Concept. Living cell. theory of the origin of life on earth. Installation by Stanley Miller. Formation of the Earth's atmosphere. Stages of the origin of life on Earth.
"Theories of biogenesis and abiogenesis" - Absence of living organisms. Theory of spontaneous generation. The heyday of the classical doctrine of spontaneous generation. Theory of spontaneous generation. Worms. Stages of the origin of life on Earth. Amino acids. Theory of biochemical evolution. Proponents of the theory of panspermia. Creationism. Theories of biogenesis and abiogenesis about the origin of living matter. Democritus. English biochemist and geneticist John Haldane. Describe the biochemical stage of chemical evolution.
"Chemical Evolution" - The Panspermia Hypothesis. Extraterrestrial origin of microorganisms. The hypothesis of spontaneous generation. Geochronology. About 8 million chemical compounds are known. The geological history of the Earth is inseparable from its biological evolution. Chemical evolution and biogenesis. Geological scale. Protostar - Sun. The sun warmed the interior. Radioactivity. Russian chemist A.P. Rudenko. As the atomic number increases, the prevalence of elements decreases.
"Theory of biochemical evolution" - Life was created by a supernatural being. The formation of a membrane structure. The hypothesis of biochemical evolution. A hypothesis that considers life as the result of a long evolution. The third stage was characterized by isolation. The concentration of substances in coacervate drops. Molecules of many substances. simple molecules. The first primitive living organisms. Long filamentous molecules. "Primary broth". One of the main features of living things is the ability to replicate.
"Hypothesis of biochemical evolution" - The process that led to the emergence of life on Earth. Origin of life on earth. Primary broth. Miller, Stanley Lloyd. Oparin-Haldane theory. Miller-Urey experiment. Various aspects. conditions for the origin of life. Hypothesis of A. I. Oparin. Coacervate drops.
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