miller experiment in hindi

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मिलर के प्रयोग का वर्णन कीजिए तथा नामांकित चित्र बनाइए। या मिलर के चिनगारी विमुक्ति उपकरण का नामांकित चित्र बनाइए।

मिलर के प्रयोग का वर्णन कीजिए तथा नामांकित चित्र बनाइए।

मिलर के चिनगारी विमुक्ति उपकरण का नामांकित चित्र बनाइए।

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स्टेनले मिलर का प्रयोग (Stanley Miller’s Experiment) – शिकागो विश्वविद्यालय के वैज्ञानिक हेरोल्ड यूरे (Harold Urey) तथा स्टेनले मिलर (Stanley Miller) ने सन् 1953 में जीवन की उत्पत्ति के सन्दर्भ में प्रयोग किये। उन्होंने आदि पृथ्वी पर पाये जाने वाले आदि वातावरण की परिस्थिति को प्रयोगशाला में उत्पन्न किया तथा जीवन की उत्पत्ति की प्रयोगशाला में जाँच की। मिलर ने एक बड़े फ्लास्क में मेथेन, अमोनिया तथा हाइड्रोजन गैस 2 : 1 : 2 के अनुपात में ली। गैसीय मिश्रण को टंगस्टन के इलेक्ट्रोड द्वारा गर्म किया गया। दूसरे फ्लास्क में जल को उबालकर जल वाष्प (water vapor-H,0) बनायी जिसे एक मुड़ी हुई काँच की नली द्वारा बड़े फ्लास्क में प्रवाहित किया। इसके उपरान्त दोनों के मिलने से बने मिश्रण को कण्डेन्सर द्वारा ठण्डा किया गया। ठण्डा मिश्रण एक U नली में एकत्रित किया गया जो गन्दे लाल रंग का द्रव था। इस प्रकार पूरे सप्ताह तक यह प्रयोग किया गया। प्रयोग द्वारा प्राप्त तरल द्रव का रासायनिक परीक्षण करने पर ज्ञात हुआ कि इसमें ग्लाइसीन (glycine); ऐलेनिन (alanine) नामक अमीनो अम्ल तथा अन्य जटिल कार्बनिक यौगिकों का निर्माण हो गया था (चित्र)।

इसी प्रकार अनेक वैज्ञानिकों; जैसे- सिडनी फॉक्स (Sydney Fox), केल्विन (Calvin) तथा मैल्विन (Melvin) आदि ने प्रयोगों द्वारा अनेक अमीनो अम्ल तथा जटिल यौगिकों का संश्लेषण किया। इन्हें अनुरूपण प्रयोग (simulation experiments) कहा जाता है।

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Miller Urey Experiment

Miller and urey experiment.

Stanley L. Muller and Harold C. Urey performed an experiment to describe the origin of life on earth. They were of the idea that the early earth’s atmosphere was able to produce amino acids from inorganic matter. The two biologists made use of methane, water, hydrogen, and ammonia which they considered were found in the early earth’s atmosphere. The chemicals were sealed inside sterile glass tubes and flasks connected together in a loop and circulated inside the apparatus.

One flask is half-filled with water and the other flask contains a pair of electrodes. The water vapour was heated and the vapour released was added to the chemical mixture. The released gases circulated around the apparatus imitating the earth’s atmosphere. The water in the flask represents the water on the earth’s surface and the water vapour is just like the water evaporating from lakes, and seas. The electrodes were used to spark the fire to imitate lightning and storm through water vapour.

The vapours were cooled and the water condensed. This condensed water trickles back into the first water flask in a continuous cycle. Miller and Urey examined the cooled water after a week and observed that 10-15% of the carbon was in the form of organic compounds. 2% of carbon had formed 13 amino acids . Yet, the Miller and Urey experiments were condemned by their fellow scientists.

Criticism of the Miller Urey Experiment

The experiment failed to explain how proteins were responsible for the formation of amino acids. A few scientists have contradicted that the gases used by Miller and Urey are not as abundant as shown in the experiment. They were of the notion that the gases released by the volcanic eruptions such as oxygen, nitrogen, and carbon dioxide make up the atmosphere. Therefore, the results are not reliable.

Oparin and Haldane

In the early 20th century, Oparin and Haldane suggested that if the atmosphere of the primitive earth was reducing and if it had sufficient supply of energy such as ultraviolet radiations and lightning, organic compounds would be synthesized at a wide range.

Oparin believed that the organic compounds would have undergone a series of reactions to form complex molecules. He suggested that the molecules formed coacervates in the aqueous environment.

Haldane proposed that the atmosphere of the primordial sea was devoid of oxygen, and was a composed of ammonia, carbon dioxide, and ultraviolet light. This gave rise to a host of organic compounds. The sea contained large amounts of organic monomers and polymers, and the sea was called a ‘hot dilute soup’. He conceived that the polymers and monomers acquired lipid membranes. The molecules further developed and gave rise to the first living organism. ‘Prebiotic soup’ was the term coined by Haldane.

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Miller-Urey Experiment

The Miller-Urey Experiment was a landmark experiment to investigate the chemical conditions that might have led to the origin of life on Earth. The scientist Stanley Miller, under the supervision of the Nobel laureate scientist Harold Urey conducted it in 1952 at the University of Chicago. They tried to recreate the conditions that could have existed in the first billion years of the Earth’s existence (also known as the Early Earth) to check the said chemical transformations.

Miller-Urey Experiment And The Primordial Soup Theory

The experiment tested the primordial or primeval soup theory developed independently by the Soviet biologist A.I. Oparin and English scientist J.B.S. Haldane in 1924 and 1929 respectively. The theory propounds the idea that the complex chemical components of life on Earth originated from simple molecules occurring naturally in the reducing atmosphere of the Early Earth, sans oxygen. Lightning and rain energized the said atmosphere to create simple organic compounds that formed an organic “soup”. The so-called soup underwent further changes giving rise to more complex organic polymers and finally life.

The Miller-Urey Experiment In Support Of Abiogenesis

From what was explained in the previous paragraph, it can undoubtedly be considered as a classic experiment to demonstrate abiogenesis. For those who are not conversant with the term, abiogenesis is the process responsible for the development of living beings from non-living or abiotic matter. It is thought to have taken place on the Earth about 3.8 to 4 billion years ago.

Miller-Urey Experiment Apparatus and Procedure

The groundbreaking experiment used a sterile glass flask of 5 liters attached with a pair of electrodes, to hold water (H 2 O), methane (CH 4 ), ammonia (NH 3 ) and hydrogen (H 2 ), the major components of primitive Earth. This was connected to another glass flask of 500 ml capacity half filled with water. On heating it, the water vaporized to fill the larger container with water vapor. The electrodes induced continuous electrical sparks in the gas mixture to simulate lightning. When the gas was cooled, the condensed water made its way into a U-shaped trap at the base of the apparatus.

After electrical sparking had continued for a day, the solution in the trap turned pink in color. At the end of a week, the boiling flask was removed, and mercuric chloride added to prevent microbial contamination. After stopping the chemical reaction, the scientist duo examined the cooled water collected to find that 10-15% of the carbon present in the system was in the form of organic compounds. 2% of carbon went into the formation of various amino acids, including 13 of the 22 amino acids essential to make proteins in living cells, glycine being the most abundant.

Though the result was the production of only simple organic molecules and not a complete living biochemical system, still the simple prebiotic experiment could, to a considerable extent, prove the primordial soup hypothesis.

Miller-Urey Experiment Animation

Chemistry of the miller and urey experiment.

The components of the mixture can react among themselves to produce formaldehyde (CH 2 O), hydrogen cyanide (HCN) and other intermediate compounds.

CO 2 → CO + [O] (atomic oxygen)

CH 4 + 2[O] → CH 2 O + H 2 O

CO + NH 3 → HCN + H 2 O

CH 4 + NH 3 → HCN + 3H 2

The ammonia, formaldehyde and HCN so produced react by a process known as Strecker synthesis to form biomolecules including amino acids.

CH 2 O + HCN + NH 3 → NH 2 -CH 2 -CN + H 2 O

NH 2 -CH 2 -CN + 2H 2 O → NH 3 + NH 2 -CH 2 -COOH (glycine)

In addition to the above, formaldehyde and water can react by Butlerov’s reaction to produce a variety of sugars like ribose, etc.

Though later studies have indicated that the reducing atmosphere as replicated by Miller and Urey could not have prevailed on primitive Earth, still, the experiment remains to be a milestone in synthesizing the building blocks of life under abiotic conditions and not from living beings themselves.

https://www.bbc.co.uk/bitesize/guides/z2gjtv4/revision/1

https://www.juliantrubin.com/bigten/miller_urey_experiment.html

Article was last reviewed on Thursday, February 2, 2023

One response to “Miller-Urey Experiment”

This experiment is currently seen as not sufficient to support abiogenesis. See Stephen C. Meyer, James Tour.

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Miller Urey Experiment: Hypothesis, Steps, Conclusions, and Limitations

The Miller Urey Experiment played a crucial role in investigating the origin of life on our planet. This comprehensive guide explores the experiment’s hypothesis, step-by-step process, key findings, and limitations, shedding light on its significance in unraveling the mysteries of life’s beginnings.

Oparin-Haldane Hypothesis

The Oparin-Haldane Hypothesis, proposed by Aleksandr Oparin and J.B.S. Haldane, postulates that life didn’t spontaneously emerge on early Earth due to different environmental conditions. It suggests that life gradually evolved from chemical reactions, starting with the combination of atoms into inorganic molecules and the subsequent formation of simple organic compounds. These compounds then assembled into complex organic structures, ultimately leading to the emergence of the first cell.

Steps of the Miller Urey Experiment

The Miller-Urey experiment, conducted in 1953 by Stanley L. Miller and Harold C. Urey, aimed to simulate early Earth’s conditions and test the Oparin-Haldane Hypothesis. Here are the key steps of the experiment:

Simulating Early Earth’s Atmosphere: The researchers recreated early Earth’s atmosphere in a closed system using a mixture of gases believed to be present during that era. They used a mixture of gases, including methane (CH4), ammonia (NH3), water vapor (H2O), and hydrogen (H2).

Introduction of Energy: Sparks or electric discharges were introduced to simulate the energy sources on early Earth, such as lightning strikes.

Circulation and Condensation: The gas mixture and energy were circulated continuously, mimicking Earth’s water cycle and allowing for the formation of various organic compounds.

Collection and Analysis: Samples were collected from the closed system and analyzed using chromatography and spectrometry to identify and characterize the organic compounds formed during the experiment.

Results and Findings: The experiment produced a variety of organic molecules, including amino acids—the building blocks of proteins —supporting the notion that early Earth’s conditions could have facilitated the synthesis of organic compounds essential for life’s origin.

Conclusions of the Miller Urey Experiment

The Miller-Urey experiment yielded significant conclusions, including:

Organic compounds, including amino acids, can be synthesized from inorganic materials under simulated early Earth conditions.
Basic building blocks of life may have emerged spontaneously from non-living matter.
The experiment demonstrated the potential for diverse organic compound formation, including rare amino acids.
External energy sources played a crucial role in facilitating chemical reactions and organic compound synthesis.
The experiment offered insights into the chemical reactions that might have occurred in early Earth’s atmosphere.
The findings supported the concept of abiogenesis, where life can arise from non-living matter through natural processes.
The Miller-Urey experiment laid the foundation for further research in prebiotic chemistry and the study of life’s origins.

Limitations of the Miller Urey Experiment

It’s important to consider the limitations of the Miller-Urey experiment, which include:

The experiment’s simulation of early Earth’s atmosphere may not perfectly represent the actual conditions.
The specific gases used may not accurately reflect the true composition of early Earth’s atmosphere.
The experiment’s short duration and scale may not fully capture the complexity and length of natural processes involved in life’s origin.
While the experiment produced organic compounds, it didn’t address the assembly of complex biomolecules or replicating systems crucial for life’s origin.

Ongoing Debates and Significance

Critics argue that the experiment oversimplifies the interconnected nature of biochemical systems and may not fully represent the processes behind life’s origin. There is an ongoing debate regarding the specific conditions and pathways leading to life’s emergence, with the Miller-Urey experiment presenting one plausible scenario. While it doesn’t address the origin of genetic information or self-replicating systems, subsequent research has refined and expanded upon its findings, leading to revised interpretations. The Miller-Urey experiment remains a significant milestone in our understanding of prebiotic chemistry and contributes to unraveling the complex puzzle of life’s origin.

In conclusion, the Miller-Urey experiment’s hypothesis, steps, conclusions, and limitations provide valuable insights into the origin of life on Earth. It serves as a foundation for further research, stimulating ongoing debates and refining our understanding of life’s emergence from non-living matter.

Learn more:

Amino Acids: Types, Functions, Sources, and Differences between Essential and Non-Essential Amino Acids

Original protocol and results

Additional trials and discoveries, significance.

Miller-Urey experiment

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Nature - The role of borosilicate glass in Miller–Urey experiment
Frontiers - Frontiers in Physics - The spark of life: discharge physics as a key aspect of the Miller–Urey experiment
National Center for Biotechnology Information - PubMed Central - Conducting Miller-Urey Experiments
National Center for Science Education - The Miller-Urey Experiment
Table Of Contents

Miller-Urey experiment , experimental simulation conducted in 1953 that attempted to replicate the conditions of Earth ’s early atmosphere and oceans to test whether organic molecules could be created abiogenically, that is, formed from chemical reactions occurring between inorganic molecules thought to be present at the time. The experiment—the results of which were published in the journal Science as “A Production of Amino Acids Under Possible Primitive Earth Conditions”—documented the production of amino acids and other organic molecules, thereby demonstrating that chemical evolution (that is, the formation of complex chemicals from simple ones) is possible. The Miller-Urey experiment is used as evidence to support hypotheses about the origins of life .

The Miller-Urey experiment was conducted by American chemist Stanley Miller under the supervision of American scientist Harold C. Urey at the University of Chicago . The experiment was designed to test ideas introduced independently in the 1920s by Russian biochemist Aleksandr Oparin and British physiologist J.B.S. Haldane , both of whom suggested that organic molecules, such as amino acids and sugars , could be formed from abiogenic materials when acted on by an external energy source within the context of a reducing atmosphere, that is, one with low levels of free oxygen ( see also oxidation-reduction reaction ). At the time, it was thought that the atmosphere of early Earth between 4 billion and 3.5 billion years ago was primarily composed of ammonia and water vapour. Oparin and Haldane noted that from this “primordial soup” of materials the first organic molecules arose, which became the precursors to molecules of ever-increasing complexity that resulted in the development of living cells ( see also abiogenesis ).

To test Oparin and Haldane’s ideas, Miller and Urey designed a closed experiment in a laboratory . They constructed an enclosed glass apparatus with two large boiling flasks connected to each other with glass tubing, in which water could pool, gases could mix, and matter could change phases between liquid and gas. A large lower chamber was filled with water (a boiling flask that stood in for the oceans), and the water was boiled to produce water vapour, which ascended into the large upper chamber (a boiling flask that simulated Earth’s early atmosphere). Additional tubing allowed material to descend from the upper chamber through a condenser, where water vapour would condense into liquid and fall into a collection trap from which samples could be taken. This trap was set slightly below the lower chamber, but it was also connected to the lower chamber above the water line. The researchers removed the air from the apparatus, replacing it throughout with ammonia, hydrogen , and methane gases, and they let the various materials cycle through liquid and gas phases.

In an early run of the experiment, Miller discovered that the energy produced from boiling water was not enough to drive the chemical reactions necessary to approximate the conditions of early Earth, so in a second version of the experiment (the one whose results were published in 1953) he added electrodes to the upper chamber. After the water was boiled, the mix of gases circulated through the system past electrodes that discharged sparks (which simulated lightning ), and a condenser converted some of the gas to liquid so that it could return to the lower chamber. This process ran continuously for one week. After this period, the contents of the apparatus had visibly changed colour. A red- and yellow-coloured solution had started to collect in the trap after running the experiment for a few days and became a broth of red and brown by the experiment’s end.

To determine the identity of the molecules that resulted from their procedure, Miller and Urey terminated the reaction, added chemicals that prevented the growth of microbes (which could be introduced to the closed system when samples were collected from the broth), extracted samples of the solution, and analyzed them using paper chromatography . They discovered several types of simple organic molecules in the samples, including amino acids, some of which were relevant as the building blocks of the proteins that are present in all living organisms. Miller was able to identify the amino acids glycine , alpha-alanine (α-alanine), and beta-alanine (β-alanine) confidently; however, he was less certain about the presence of aspartic acid and α-amino- n -butyric acid, whose signs in the analysis were weak.

Miller modified the original experiment several times, and each modification captured possible variations in Earth conditions that might influence the system’s products. Some of Miller’s subsequent experiments used different energy sources, such as an electrical source that produced a silent discharge instead of a spark, and improved gas circulation through the addition of glass tubing. Other researchers also repeated the experiment during the 1950s using different energy sources, such as ultraviolet light , and used different atmospheric gases (such as carbon dioxide , hydrogen sulfide , and nitrogen ) in various combinations, which also resulted in a mix of organic chemicals but only a handful of amino acids.

Miller and others would repeat the experiment several times in subsequent decades. He reran the experiment in the early 1970s using better analytical equipment, which revealed the presence of 33 different amino acids, including more than half of the 20 or so that appear in proteins present in living things. Researchers later criticized Miller for using what they considered to be the wrong gases in the experiment; carbon dioxide and nitrogen, not ammonia and methane, were shown later to be the primary gases in Earth’s early atmosphere, with ammonia and methane occurring only in minor amounts. Miller’s 1983 trial replaced methane and ammonia with carbon dioxide and nitrogen; however, fewer amino acids were produced than in the original published experiment. This result was attributed later to a buildup of nitrites in the system, which made the mixture more acidic and caused the amino acids to break down before they could be identified.

American chemist Jeffrey Bada of the Scripps Institution of Oceanography reran the experiment in 2007. In addition to simulating an atmosphere filled with carbon dioxide and nitrogen, he added iron and carbonates to the system (two materials that would have been present in large amounts on ancient Earth)—which neutralized both the nitrites and the acids in the system, thereby allowing the amino acids to persist. A group of Spanish and Italian researchers suggested in 2021 that materials in the glass apparatus itself may have also catalyzed the chemical reactions taking place within it; the various chemicals in the experiment were shown to have reacted with the interior surface of the glass to release silicates (which, in turn, reacted with other chemicals) while also leaving behind small imperfections and cracks on the interior surface that may have served as chambers for other chemical reactions.

Starting in the early 2000s, researchers examined archived vials containing samples of material collected from Miller’s experiments during the 1950s. Aided by modern analytical equipment, they discovered far more than the five amino acids Miller reported in his papers; Miller’s experiments conducted in 1953 and 1958 were each shown to have yielded more than 20 amino acids.

The experiment showed that amino acids, which are important components of proteins (which are critical to life on Earth), could have arisen from inorganic compounds during Earth’s prebiotic phase. It also demonstrated that the speculation that life could have originated through chemical reactions among nonliving materials is possible and that this hypothesis could be tested scientifically. The Miller-Urey experiment sparked research on how simple organic molecules might polymerize into more complex molecules, a process that may have produced the first living cells. Scientists have also considered the possibility that meteors brought the first organic molecules, formed in space, to Earth, and they continue to modify the Miller-Urey protocol to test new ideas about chemical reactions in primitive Earth conditions.

Explain the miller's experiment with the help of diagram?

Stanley miller was an american chemist who conducted one of the most exciting experiments in modern science. he and harold c. urey conducted an experiment to understand the origin of life. miller took molecules that represent the major components of the early earth's atmosphere and put them into a closed system. the gases used were methane (ch4), ammonia (nh3), hydrogen (h2), and water (h2o). electric current was passed through the system, to simulate lightning storms believed to be common on the early earth. analysis of the experiment was done by chromatography. at the end of one week, they observed that as much as 10-15% of the carbon was now in the form of organic compounds. two per cent of the carbon had formed some of the amino acids which are used to make proteins. thus this experiment showed that organic compounds such as amino acids, which are essential to cellular life, could be made easily under the conditions believed to be present on the early earth..

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Conducting Miller-Urey Experiments

Eric t. parker.

1 School of Chemistry and Biochemistry, Georgia Institute of Technology

James H. Cleaves

2 Earth-Life Science Institute, Tokyo Institute of Technology

3 Institute for Advanced Study

Aaron S. Burton

4 Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center

Daniel P. Glavin

5 Goddard Center for Astrobiology, NASA Goddard Space Flight Center

Jason P. Dworkin

Manshui zhou, jeffrey l. bada.

6 Geosciences Research Division, Scripps Institution of Oceanography, University of California at San Diego

Facundo M. Fernández

In 1953, Stanley Miller reported the production of biomolecules from simple gaseous starting materials, using an apparatus constructed to simulate the primordial Earth's atmosphere-ocean system. Miller introduced 200 ml of water, 100 mmHg of H 2 , 200 mmHg of CH 4 , and 200 mmHg of NH 3 into the apparatus, then subjected this mixture, under reflux, to an electric discharge for a week, while the water was simultaneously heated. The purpose of this manuscript is to provide the reader with a general experimental protocol that can be used to conduct a Miller-Urey type spark discharge experiment, using a simplified 3 L reaction flask. Since the experiment involves exposing inflammable gases to a high voltage electric discharge, it is worth highlighting important steps that reduce the risk of explosion. The general procedures described in this work can be extrapolated to design and conduct a wide variety of electric discharge experiments simulating primitive planetary environments.

Introduction

The nature of the origins of life on Earth remains one of the most inscrutable scientific questions. In the 1920s Russian biologist Alexander Oparin and British evolutionary biologist and geneticist John Haldane proposed the concept of a "primordial soup" 1,2 , describing the primitive terrestrial oceans containing organic compounds that may have facilitated chemical evolution. However, it wasn't until the 1950s when chemists began to conduct deliberate laboratory studies aimed at understanding how organic molecules could have been synthesized from simple starting materials on the early Earth. One of the first reports to this end was the synthesis of formic acid from the irradiation of aqueous CO 2 solutions in 1951 3 .

In 1952, Stanley Miller, then a graduate student at the University of Chicago, approached Harold Urey about doing an experiment to evaluate the possibility that organic compounds important for the origin of life may have been formed abiologically on the early Earth. The experiment was conducted using a custom-built glass apparatus ( Figure 1A ) designed to simulate the primitive Earth. Miller's experiment mimicked lightning by the action of an electric discharge on a mixture of gases representing the early atmosphere, in the presence of a liquid water reservoir, representing the early oceans. The apparatus also simulated evaporation and precipitation through the use of a heating mantle and a condenser, respectively. Specific details about the apparatus Miller used can be found elsewhere 4 . After a week of sparking, the contents in the flask were visibly transformed. The water turned a turbid, reddish color 5 and yellow-brown material accumulated on the electrodes 4 . This groundbreaking work is considered to be the first deliberate, efficient synthesis of biomolecules under simulated primitive Earth conditions.

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Figure 1. Comparison between the two types of apparatuses discussed in this paper. The classic apparatus used for the original Miller-Urey experiment ( A ) and the simplified apparatus used in the protocol outlined here ( B ). Click here to view larger image .

After the 1953 publication of results from Miller's classic experiment, numerous variations of the spark discharge experiment, for example using other gas mixtures, were performed to explore the plausibility of producing organic compounds important for life under a variety of possible early Earth conditions. For example, a CH 4 /H 2 O/NH 3 /H 2 S gas mixture was tested for its ability to produce the coded sulfur-containing α-amino acids, although these were not detected 6 . Gas chromatography-mass spectrometry (GC-MS) analysis of a CH 4 /NH 3 mixture subjected to an electric discharge showed the synthesis of α-aminonitriles, which are amino acid precursors 7 . In 1972, using a simpler apparatus, first introduced by Oró 8 ( Figure 1B ), Miller and colleagues demonstrated the synthesis of all of the coded α-amino acids 9 and nonprotein amino acids 10 that had been identified in the Murchison meteorite to date, by subjecting CH 4 , N 2 , and small amounts of NH 3 to an electric discharge. Later, using this same simplified experimental design, gas mixtures containing H 2 O, N 2 , and CH 4 , CO 2 , or CO were sparked to study the yield of hydrogen cyanide, formaldehyde, and amino acids as a function of the oxidation state of atmospheric carbon species 11 .

In addition to the exploration of alternative experimental designs over the years, significant analytical advances have occurred since Miller's classic experiment, which recently aided more probing investigations of electric discharge experimental samples archived by Miller, than would have been facilitated by the techniques Miller had access to in the 1950s. Miller's volcanic experiment 12 , first reported in 1955 4 , and a 1958 H 2 S-containing experiment 13 were shown to have formed a wider variety, and greater abundances, of numerous amino acids and amines than the classic experiment, including many of which that had not been previously identified in spark discharge experiments.

The experiment described in this paper can be conducted using a variety of gas mixtures. Typically, at the very least, such experiments will contain a C-bearing gas, an N-bearing gas, and water. With some planning, almost any mixture of gases can be explored, however, it is important to consider some chemical aspects of the system. For example, the pH of the aqueous phase can have a significant impact on the chemistry that occurs there 14 .

The method described here has been tailored to instruct researchers how to conduct spark discharge experiments that resemble the Miller-Urey experiment using a simplified 3 L reaction vessel, as described in Miller's 1972 publications 9,10 . Since this experiment involves a high voltage electric arc acting on inflammable gases, it is crucial to remove O 2 from the reaction flask to eliminate the risk of explosion, which can occur upon combustion of reduced carbon-bearing gases such as methane or carbon monoxide, or reaction of H 2 with oxygen.

There are additional details that should be kept in mind when preparing to conduct the experiment discussed here. First, whenever working with glass vacuum lines and pressurized gases, there exists the inherent danger of both implosion and over-pressuring. Therefore, safety glasses must be worn at all times. Second, the experiment is typically conducted at less than atmospheric pressure. This minimizes the risk of over-pressuring the manifold and reaction flask. Glassware may be rated at or above atmospheric pressure, however, pressures above 1 atm are not recommended. Pressures may increase in these experiments as water-insoluble H 2 is liberated from reduced gases (such as CH 4 and NH 3 ). Over-pressuring can lead to seal leakage, which can allow atmospheric O 2 to enter the reaction flask, making it possible to induce combustion, resulting in an explosion. Third, it should be borne in mind that modification of this protocol to conduct variations of the experiment requires careful planning to ensure unsafe conditions are not created. Fourth, it is highly recommended that the prospective experimenter read through the entire protocol carefully several times prior to attempting this experiment to be sure he or she is familiar with potential pitfalls and that all necessary hardware is available and in place. Lastly, conducting experiments involving combustible gases require compliance with the experimenter's host institution's Environmental Health and Safety departmental guidelines. Please observe these recommendations before proceeding with any experiments. All steps detailed in the protocol here are in compliance with the authors' host institutional Environmental Health and Safety guidelines.

1. Setting Up a Manifold/Vacuum System

Use ground glass joints and glass plugs with valves on the manifold. Ensure that all O-rings on the plugs are capable of making the necessary seals. If using glass joints, a sufficient amount of vacuum grease can be applied to help make a seal, if necessary. Silicon vacuum grease can be used to avoid potential organic contamination.
Use glass stopcocks on the manifold. Apply the minimum amount of vacuum grease necessary to make a seal.
Measure the manifold volume. This volume will be used for calculations related to final gas pressures in the 3 L reaction flask and should be known as precisely as possible.
Unless the manifold has enough connections to accommodate all gas cylinders simultaneously, connect one cylinder at a time to the manifold. Include in this connection, a tap allowing the manifold to be isolated from the ambient atmosphere.
Use suitable, clean, inert, and chemical and leak resistant tubing and ultratorr vacuum fittings to connect the gas cylinders to the manifold. Ultratorr fittings, where used, are to be finger-tightened.
To ensure rapid attainment of vacuum and to protect the pump, insert a trap between the manifold and the vacuum pump. A liquid nitrogen finger-trap is recommended as it will prevent volatiles such as NH 3 , CO 2 , and H 2 O from entering the pump. Care should be taken, as trapped volatiles, upon warming, may overpressure the manifold and result in glass rupture.
Connect to the manifold, a manometer or other vacuum gauge capable of 1 mmHg resolution or better. While various devices can be used, a mercury manometer, or MacLeod gauge, is preferable as mercury is fairly nonreactive.
Measure and record the ambient temperature using a suitable thermometer.

2. Preparation of Reaction Flask

Clean the tungsten electrodes by gently washing with clean laboratory wipes and methanol, and drying in air.
Introduce a precleaned and sterilized magnetic stir bar, which will ensure rapid dissolution of soluble gases and mixing of reactants during the experiment.
Attach the tungsten electrodes to the 3 L reaction flask using a minimal amount of vacuum grease, with tips separated by approximately 1 cm inside the flask. Fasten with clips.
Insert an adapter with a built-in stopcock into the neck of the 3 L reaction flask and secure with a clip.
Lightly grease all connections to ensure a good vacuum seal.
Open all valves and stopcocks on the manifold, except Valve 6 and Stopcock 1 ( Figure 4 ), and turn on the vacuum pump to evacuate the manifold. Once a stable vacuum reading of <1 mmHg has been attained, close Valve 1 and allow the manifold to sit for ~15 min to check for vacuum leaks. If none are detected, proceed to step 2.8. Otherwise troubleshoot the various connections until the leaks can be identified and fixed.
Apply magnetic stirring to the reaction vessel. Open Valve 1 and Stopcock 1 ( Figure 4 ) to evacuate the headspace of the 3 L reaction flask until the pressure has reached <1 mmHg.
Close Valve 1 ( Figure 4 ) and monitor the pressure inside the 3 L reaction flask. The measured pressure should increase to the vapor pressure of water. To ensure that no leaks exist, wait ~5 min at this stage. If the pressure (as read on the manometer) increases while Valve 1 is closed during this step, check for leaks in Stopcock 1 and the various reaction flask connections. If no leak is found, proceed to the next step.

3. Introduction of Gaseous NH 3

Calculate the necessary pressure of gaseous NH 3 to introduce into the manifold such that 200 mmHg of NH 3 will be introduced into the reaction flask. Details on how to do this are provided in the Discussion section.
Close Valves 1 and 6, and Stopcock 1 ( Figure 4 ) before introducing any gas into the manifold. Leave the other valves and stopcock open.
Introduce NH 3 into the manifold until a small pressure (approximately 10 mmHg) is reached and then evacuate the manifold to a pressure of <1 mmHg by opening Valve 1 ( Figure 4 ). Repeat 3x.
Introduce NH 3 into the manifold to reach the pressure determined in step 3.1.
Open Stopcock 1 ( Figure 4 ) to introduce 200 mmHg of NH 3 into the 3 L reaction flask. The NH 3 will dissolve in the water in the reaction flask and the pressure will fall slowly.
Once the pressure stops dropping, close Stopcock 1 ( Figure 4 ) and record the pressure read by the manometer. This value represents the pressure inside the flask and will be used to calculate the pressures for other gases that will be introduced into the manifold later.
Open Valve 1 ( Figure 4 ) to evacuate the manifold to a pressure of <1 mmHg.
Close Valve 2 ( Figure 4 ) and disconnect the NH 3 gas cylinder from the manifold.

4. Introduction of CH 4

Calculate the necessary pressure of CH 4 to be introduced into the manifold such that 200 mmHg of CH 4 will be introduced into the 3 L reaction flask. Example calculations are shown in the Discussion section.
Connect the CH 4 gas cylinder to the manifold.
Open all valves and stopcocks, except Valve 6 and Stopcock 1 ( Figure 4 ), and evacuate the manifold to a pressure of <1 mmHg.
Close Valve 1 once the manifold has been evacuated ( Figure 4 ).
Introduce CH 4 into the manifold until a small pressure (approximately 10 mmHg) is obtained. This purges the line of any contaminant gases from preceding steps. Open Valve 1 ( Figure 4 ) to evacuate the manifold to <1 mmHg. Repeat 2x more.
Introduce CH 4 into the manifold until the pressure calculated in step 4.1, is reached.
Open Stopcock 1 ( Figure 4 ) to introduce 200 mmHg of CH 4 into the 3 L reaction flask.
Close Stopcock 1 once the intended pressure of CH 4 has been introduced into the 3 L reaction flask ( Figure 4 ) and record the pressure measured by the manometer.
Open Valve 1 (Figure 4 ) to evacuate the manifold to <1 mmHg.
Close Valve 2 ( Figure 4 ) and disconnect the CH 4 cylinder from the manifold.

5. Introduction of Further Gases ( e.g. N 2 )

At this point, it is not necessary to introduce additional gases. However, if desired, it is recommended to add 100 mmHg of N 2 . In this case, calculate the necessary pressure of N 2 to be introduced into the manifold such that 100 mmHg of N 2 will be introduced into the 3 L reaction flask. Example calculations are shown in the Discussion section.
Connect the N 2 gas cylinder to the manifold.
Introduce N 2 into the manifold until a small pressure (approximately 10 mmHg) is obtained. Open Valve 1 ( Figure 4 ) to evacuate the manifold to <1 mmHg. Repeat 2x more.
Introduce N 2 into the manifold until the pressure calculated in step 5.1 is reached.
Open Stopcock 1 ( Figure 4 ) to introduce 100 mmHg of N 2 into the reaction flask.
Close Stopcock 1 once the intended pressure of N 2 has been introduced into the reaction flask, ( Figure 4 ) and record the pressure using the manometer.
Open Valve 1 ( Figure 4 ) to evacuate the manifold to <1 mmHg.
Close Valve 2 ( Figure 4 ) and disconnect the N 2 cylinder from the manifold.

6. Beginning the Experiment

Detach the reaction flask from the manifold by closing Stopcock 1 and Valve 1 ( Figure 4 ) once all gases have been introduced into the reaction flask, so that ambient air may enter the manifold and bring the manifold up to ambient pressure.
After carefully disconnecting the reaction flask from the manifold, set the flask somewhere it will not be disturbed ( e.g. inside an empty fume hood).
Disconnect the vacuum pump and carefully remove the cold trap and allow venting inside a fully operational fume hood.
Secure the Tesla coil connected to the high frequency spark generator.
Connect the opposite tungsten electrode to an electrical ground to enable the efficient passage of electrical current across the gap between the two electrodes.
Set the output voltage of the spark generator to approximately 30,000 V, as detailed by documents available from the manufacturer.
Prior to initiating the spark, close the fume hood sash, to serve as a safety shield between the apparatus and the experimenter. Turn the Tesla coil on to start the experiment, and allow sparking to continue for 2 weeks (or other desired period) in 1 hr on/off cycles.

7. End of Experiment

Stop the experiment by turning off the Tesla coil.
Open Stopcock 1 ( Figure 4 ) to slowly introduce ambient air into the reaction flask and facilitate the removal of the adapter and the tungsten electrodes so samples can be collected. If desired, a vacuum can be used to evacuate the reaction flask of noxious reaction gases.

8. Collecting Liquid Sample

Transfer the sample to a sterile plastic or glass receptacle. Plastic receptacles are less prone to cracking or breaking upon freezing, compared to glass receptacles.
Seal sample containers and store in a freezer capable of reaching temperatures of -20 °C or lower, as insoluble products may prevent the sample solution from freezing at 0 °C.

9. Cleaning the Apparatus

Use clean laboratory wipes to carefully remove vacuum grease from the neck of the apparatus, the adapter and stopcock, and the glass surrounding the tungsten electrodes.
Thoroughly clean the same surfaces described in step 9.1 with toluene to fully remove organic vacuum grease from the glassware. If using silicon grease, the high vacuum grease may remain on the glassware after pyrolysis, creating future problems, as detailed in the Discussion section.
Thoroughly clean the reaction flask with a brush and the following solvents in order: ultrapure water (18.2 MΩ cm, <5 ppb TOC), ultrapure water (18.2 MΩ cm, <5 ppb TOC) with 5% cleaning detergent, methanol, toluene, methanol, ultrapure water (18.2 MΩ cm, <5 ppb TOC) with 5% cleaning detergent, and finally ultrapure water (18.2 MΩ cm, <5 ppb TOC).
Cover all open orifices of the reaction flask with aluminum foil and wrap the adapter and its components in aluminum foil.
Once all the glassware has been wrapped in aluminum foil, pyrolyze for at least 3 hr in air at 500 °C.
Gently clean electrodes with methanol and let air dry.

10. Sample Analysis

Note: When preparing samples for analysis, the use of an acid hydrolysis protocol such as has been described in detail elsewhere 15 , is useful for obtaining more amino acids. Hydrolysis of a portion of the recovered sample provides the opportunity to analyze both free amino acids as well as their acid-labile precursors that are synthesized under abiotic conditions.

For amino acid analysis, use a suitable technique (such as liquid chromatography and mass spectrometry-based methods, or other appropriate approaches). Such analytical techniques include high performance liquid chromatography with fluorescence detection (HPLC-FD) 14 , and ultrahigh performance liquid chromatography with fluorescence detection in parallel with time-of-flight positive electrospray ionization mass spectrometry (UHPLC-FD/ToF-MS) 12,13 . This manuscript describes analysis using mass spectrometric analyses via a triple quadrupole mass spectrometer (QqQ-MS) in conjunction with HPLC-FD.

Representative Results

The products synthesized in electric discharge experiments can be quite complex, and there are numerous analytical approaches that can be used to study them. Some of the more commonly used techniques in the literature for analyzing amino acids are discussed here. Chromatographic and mass spectrometric methods are highly informative techniques for analyzing the complex chemical mixtures produced by Miller-Urey type spark discharge experiments. Amino acid analyses can be conducted using o -phthaldialdehyde/N-acetyl-L-cysteine (OPA/NAC) 16 , a chiral reagent pair that tags primary amino groups, yielding fluorescent diastereomer derivatives that can be separated on an achiral stationary phase. Figure 2 shows a chromatogram of an OPA/NAC-derivatized amino acid standard obtained by HPLC coupled to fluorescence detection and QqQ-MS. The amino acids contained in the standard include those typically produced in Miller-Urey type spark discharge experiments. The identities of these amino acids are listed in Table 1 . Representative fluorescence traces of a typical sample and analytical blank are shown in Figure 3 , demonstrating the molecular complexity of Miller-Urey type electric discharge samples. The sample chromatogram in Figure 3 was produced from a spark discharge experiment using the following starting conditions: 300 mmHg of CH 4 , 250 mmHg of NH 3 , and 250 ml of water.

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Figure 2. The 3-21 min region of the HPLC-FD/QqQ-MS chromatograms produced from the analysis of an OPA/NAC-derivatized amino acid standard . Amino acid peak identities are listed in Table 1 . The fluorescence trace is shown at the bottom and the corresponding extracted mass chromatograms are shown above. The electrospray ionization (ESI) QqQ-MS was operated in positive mode and monitored a mass range of 50-500 m/z. The ESI settings were: desolvation gas (N 2 ) temperature: 350 °C, 650 L/hr; capillary voltage: 3.8 kV; cone voltage: 30 V. The unlabeled peaks in the 367 extracted ion chromatogram are the 13 C 2 peaks from the 365 extracted ion chromatogram, as a result of the approximately 1% natural abundance of 13 C. Click here to view larger image .

Peak	Amino Acid
1	D-aspartic acid
2	L-aspartic acid
3	L-glutamic acid
4	D-glutamic acid
5	D-serine
6	L-serine
7	Glycine
8	b-Alanine
9	D-alanine
10	g-amino-n-butyric acid (g-ABA)
11	L-alanine
12	D-b-amino-n-butyric acid (D-b-ABA)
13	a-aminoisobutyric acid (a-AIB)
14	L-b-amino-n-butyric acid (L-b-ABA)
15	D/L-a-amino-n-butyric acid (D/L-a-ABA)
16	D-isovaline
17	L-isovaline
18	L-valine
19	e-amino-n-caproic acid (EACA)
20	D-valine
21	D-isoleucine
22	L-isoleucine
23	D/L-leucine

Table 1. Peak identities for amino acids detected in the standard and that are typically produced in Miller-Urey type spark discharge experiments.

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Figure 3. The 3-21 min region of the HPLC-FD chromatograms representative of Miller-Urey type spark discharge experiments. Peaks were identified and quantitated by retention time and mass analysis of target compounds compared to a standard and analytical blank. All target analytes with coeluting fluorescence retention times can be separated and quantitated using mass spectrometry, except for α-AIB and L-β-ABA (peaks 13 and 14), and D/L-norleucine, which coelutes with D/L-leucine (peak 23), under the chromatographic conditions used. D/L-norleucine was added as an internal standard to samples and analytical blanks during sample preparation. Amino acid separation was achieved using a 4.6 mm x 250 mm, 5 μm particle size Phenyl-Hexyl HPLC column. The mobile phase was composed of: A) ultrapure water (18.2 MΩ cm, <5 ppb TOC), B) methanol, and C) 50 mM ammonium formate with 8% methanol, at pH 8. The gradient used was: 0-5 min, 100% C; 5-15 min, 0-83% A, 0-12% B, 100-5% C; 15-22 min, 83-75% A, 12-20% B, 5% C; 22-35 min, 75-35% A, 20-60% B, 5% C; 35-37 min, 35-0% A, 60-100% B, 5-0% C; 37-45 min, 100% B; 45-46 min, 100-0% B, 0-100% C 46-55 min, 100% C. The flow rate was 1 ml/min. Click here to view larger image .

Numerous steps in the protocol described here are critical for conducting Miller-Urey type experiments safely and correctly. First, all glassware and sample handling tools that will come in contact with the reaction flask or sample need to be sterilized. Sterilization is achieved by thoroughly rinsing the items in question with ultrapure water (18.2 MΩ cm, <5 ppb TOC) and then wrapping them in aluminum foil, prior to pyrolyzing at 500 °C in air for at least 3 hr. Once the equipment has been pyrolyzed and while preparing samples for analysis, care must be taken to avoid organic contamination. The risk of contamination can be minimized by wearing nitrile gloves, a laboratory coat, and protective eyewear. Be sure to work with samples away from one's body as common sources of contamination include finger prints, skin, hair, and exhaled breath. Avoid contact with wet gloves and do not use any latex or Nylon materials. Second, thorough degassing of the reaction flask prior to gas addition into the reaction flask is critical. The presence of even small amounts of molecular oxygen in the reaction flask poses an explosion risk when the spark is discharged into inflammable gases such as CH 4 . While degassing the flask, the water inside the flask will boil, which will prevent a stable reading. At this stage there are two options: 1) degas the flask via freeze-thaw cycles (typically 3 are used), or 2) simply degas the liquid solution. In the latter case, some water will be lost, however, the amount will be relatively minor compared to the remaining volume. Third, a well-equipped and efficient setup must be carefully constructed to establish a consistent spark across the electrodes throughout the entirety of the experiment. BD-50E Tesla coils are not designed for prolonged operation, as they are intended for vacuum leak detection. Intermittent cooling of the Tesla coil is thus recommended for extended operational lifetime. There are multiple ways of achieving this. One simple way is to attach a timer in-line between the spark tester and its power supply and program the timer such that it alternates in 1 hour on/off cycles. Cooling the Tesla coil with a commercial fan may also be necessary to prolong the life of the Tesla coil. The Tesla coil tip should be touching or almost touching one of the tungsten electrodes; a distance between the two of approximately 1 mm or less. Additionally, an intense discharge can be achieved using a length of conductive metal wire with a loop in one end draped lightly over the electrode opposite the one touching the Tesla coil to avoid breaking the seal to the contents. It is also recommended to have a second spark generator available in case the primary spark generator fails due to extended use.

There are many additional notes worth keeping in mind when carrying out various steps in the protocol outlined here. When preparing the manifold system for an experiment and using a mercury manometer, it is generally conceded that a precision of 1 mmHg is the best achievable, due to the resolution of the human eye. Some gases may present conductivity problems with resistance-based gauges. Mercury manometers present potential spill hazards, which should be prepared for in advance.

While assembling the 3 L reaction flask, the use of silicon vacuum grease can mitigate potential organic contamination, but care should be taken to remove this thoroughly between runs. Failure to do so will result in the accumulation of silica deposits during high-temperature pyrolysis, which can interfere with vacuum seals. Additionally, the tungsten electrodes are commercially available as 2% thoriated tungsten and should be annealed into half-round ground glass fittings . Do not pyrolyze the glass-fitted tungsten electrodes in an oven. The coefficients of thermal expansion of tungsten and glass are different and heating above 100 °C may weaken the seal around the glass annealed electrodes and introduce leaks to the system. Also, ultrapure water can be introduced into the 3 L reaction flask by pouring, using care to avoid contact with any grease on the port used, or by pipetting, using a prepyrolyzed glass pipette. The aqueous phase in the reaction flask can be buffered, if desired. For example, Miller and colleagues 9 buffered the solution to pH ~8.7 with an NH 3 /NH 4 Cl buffer. To do this the aqueous phase is made 0.05 M in NH 4 Cl prior to introducing it into the reaction flask. NH 4 Cl of 99.5% purity, or greater, should be used. The remainder of the NH 3 is then added to the reaction flask as a gas.

In preparation for gas introduction into the 3 L reaction flask, the flask can be secured onto the manifold by placing the flask on a cork ring, set atop a lab jack and gently raising the flask assembly until a snug connection is achieved. When checking for leaks, it is worth noting that likely sources of leaks include poor seals at the junctions of the half-round ground glass joints, which attach the tungsten electrodes to the reaction flask, and the stopcock of the adapter attached to the neck of the 3 L reaction flask. If leaks from these sources are detected, carefully remove the 3 L reaction flask from the manifold, wipe these areas with clean laboratory tissue, reapply a fresh coating of vacuum grease and reattach the flask to the manifold to search for leaks. If no leaks are found, proceed to introduce gases into the reaction flask.

While introducing gases into the apparatus, gas cylinders should be securely fastened to a support. Care should be taken to introduce gases slowly. Valves on gas cylinders should be opened slowly and carefully while monitoring the manometer to avoid over-pressuring the glassware and attached fittings. It is important to note that while adding NH 3 into the reaction flask, because NH 3 is appreciably soluble in water below the pK a of NH 4 + (~9.2), essentially all of the NH 3 gas introduced into the manifold will dissolve in the aqueous phase, rendering the final pressure in the flask and manifold as the vapor pressure of water at the ambient temperature. Once this pressure is attained, one may assume the transfer is complete. The following are examples of the calculations that must be executed in order to precisely introduce gases into the reaction flask at their desired pressures:

Introduction of Gaseous NH 3

Due to the solubility of NH 3 , essentially all of it will transfer from the manifold to the reaction flask and dissolve in the aqueous phase as long as the NH 3 in the manifold is at a higher pressure than the vapor pressure of water in the reaction flask. Therefore, the ambient temperature should be noted and the vapor pressure of water at that temperature should be referenced prior to introducing NH 3 into the manifold. The target pressure of NH 3 to be introduced into the reaction flask should be equal to the target pressure of NH 3 in the 3 L reaction flask, plus the vapor pressure of water in the reaction flask, at the recorded ambient temperature. For example, at 25 °C, the vapor pressure of water is approximately 24 mmHg. Thus, in order to introduce 200 mmHg of NH 3 into the reaction flask, load roughly 225 mmHg of NH 3 into the manifold prior to transferring NH 3 from the manifold and into the reaction flask. This will result in approximately 200 mmHg of NH 3 being introduced into the reaction flask.

Introduction of CH 4

After NH 3 addition and its dissolution in the aqueous phase, the pressure in the headspace of the reaction flask will be equal to the vapor pressure of water at 25 °C, approximately 24 mmHg. This value will be used, in conjunction with the example manifold shown in Figure 4 , to carry out a calculation for how much CH 4 to introduce into the manifold such that 200 mmHg of CH 4 will be introduced into the reaction flask:

P 1 = total pressure desired throughout the entire system, including the reaction flask V 1 = total volume of the entire system, including the reaction flask

P 2 = pressure of CH 4 needed to fill manifold volume prior to introduction into reaction flask V 2 = volume of manifold used for gas introduction

P 3 = pressure already in the headspace of the reaction flask V 3 = volume of the reaction flask

P 1 = 200 mmHg of CH 4 + 24 mmHg of H 2 O = 224 mmHg V 1 = 3,000 ml + 100 ml + 300 ml + 40 ml + 20 ml + 3,000 ml + 40 ml + 500 ml = 7,000 ml

P 2 = pressure of CH 4 being calculated V 2 = 100 ml + 300 ml + 40 + 20 + 3,000 ml+ 40 ml + 500 ml = 4,000 ml

P 3 = 24 mmHg of H 2 O V 3 = 3,000 ml

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Introduction of N 2

After introduction of CH 4 , the headspace of the reaction flask is occupied by 200 mmHg of CH 4 and 24 mmHg of H 2 O for a total of 224 mmHg. This value will be used, along with the dimensions of the example manifold shown in Figure 4 , to calculate the N 2 pressure that needs to be introduced into the manifold such that 100 mmHg of N 2 will be introduced into the reaction flask:

P 2 = pressure of N 2 needed to fill manifold volume prior to introduction into reaction flask V 2 = volume of manifold used for gas introduction

P 1 = 24 mmHg of H 2 O + 200 mmHg of CH 4 + 100 mmHg of N 2 = 324 mmHg V 1 = 3,000 ml + 100 ml > + 300 ml + 40 ml + 20 ml + 3,000 ml + 40 ml + 500 ml = 7,000 ml

P 2 = pressure of N 2 being calculated V 2 = 100 ml + 300 ml + 40 ml + 20 ml + 3,000 ml + 40 ml + 500 ml = 4,000 ml

P 3 = 200 mmHg of CH 4 + 24 mmHg of H 2 O = 224 mmHg V 3 = 3,000 ml

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Figure 4. Manifold/vacuum system used to introduce gases into the 3 L reaction flask. Valves controlling gas flow are labeled as V 1 - V 8 , while stopcocks controlling gas flow are labeled as S 1 and S 2 . It is worth noting that while Valves 1, 2, and 6, and Stopcock 1 are referred to explicitly in the protocol, the other valves and stopcock in the manifold shown here are useful for adding or removing volume ( i.e. holding flasks) to or from the manifold. For example, when introducing gases into the manifold at relatively high pressures (approximately 500 mmHg or greater), it is advised that the experimenter makes use of all purge flasks attached to the manifold to increase the accessible volume of the manifold and help minimize the risk of over-pressuring the manifold.

After initiating the experiment, the system must be checked on regularly to ensure the experiment is running properly. Things to check include: 1) the spark generator is producing a spark, and 2) the spark is being generated across the tungsten electrodes in a continuous manner. If the above conditions are not met, disconnect the Tesla coil from its power supply and replace it with the backup Tesla coil. Meanwhile, repairs to the malfunctioning Tesla coil can be made. Often times, the contact plates inside the spark generator housing can become corroded from extended use and should be polished, or replaced.

Upon completion of the experiment, the gases in the head-space may be irritating to the respiratory system. Harmful gases, such as hydrogen cyanide 4 can be produced by the experiment. If the experimenter is not collecting gas samples for analysis, it may be helpful to connect the apparatus to a water aspirator to evacuate volatiles for approximately one hour after completion of the experiment, while the apparatus remains in the fume hood, prior to collecting liquid samples. For safety reasons, it is advised that the apparatus is vented in a fully-operational fume hood. Sample collection should be performed in an operational fume hood and sample handling in a positive-pressure HEPA filtered flow bench is recommended.

Among the numerous types of products formed by spark discharge experiments, amino acids are of significance. Amino acids are synthesized readily via the Strecker synthesis 17 . The Strecker synthesis of amino acids involves the reaction of aldehydes or ketones and HCN generated by the action of electric discharge on the gases introduced into the reaction apparatus, which upon dissolving in the aqueous phase, may react with ammonia to form α-aminonitriles that undergo hydrolysis to yield amino acids. This is, of course, but one mechanism of synthesis, and others may also be operative, such as direct amination of precursors including acrylonitrile to give β-alanine precursors, or direct hydrolysis of higher molecular weight tholin-like material to give amino acids directly, by-passing the Strecker mechanism.

Amino acid contamination of the samples produced by Miller-Urey experiments can occur if the precautions mentioned earlier are not followed explicitly. During sample analysis, it is important to search for signs of terrestrial contamination that may have originated from sample handling or sample storage. The use of OPA/NAC 16 in conjunction with LC-FD techniques allows for the chromatographic separation of D- and L-enantiomers of amino acids with chiral centers and their respective, individual quantitation. Chiral amino acids synthesized by the experiment should be racemic. Acceptable experimental error during the synthesis of amino acids with chiral centers is generally considered to be approximately 10%. Therefore chiral amino acid D/L ratios suggestive of enrichment in one enantiomer by more than 10% is a good metric by which to determine if the sample has been contaminated.

The methods presented here are intended to instruct how to conduct a Miller-Urey type spark discharge experiment; however, there are limitations to the technique described here that should be noted. First, heating the single 3 L reaction flask ( Figure 1B ), will result in condensation of water vapor onto the tips of the electrodes, dampening the spark, and reducing the generation of radical species that drive much of the chemistry taking place within the experiment. Furthermore, the use of a heating mantle to heat the apparatus is not necessary to synthesize organic compounds, such as amino acids. This differs from Miller's original experiment where he used a more complex, custom-built, dual flask apparatus ( Figure 1A ) 5 and heated the small flask at the bottom of the apparatus, which had water in it ( Figure 1A ). Heating the apparatus helped with circulation of the starting materials and aimed to mimic evaporation in an early Earth system. Second, the protocol detailed here recommends a 1 hr on/off cycle when using the Tesla coil, which effectively doubles the amount of time an experiment takes to complete, compared to the experiments conducted by Miller, as he continuously discharged electricity into the system 4 . Third, as spark generators are not intended for long-term use, they are prone to malfunction during prolonged use and must be regularly maintained and sometimes replaced by a back-up unit, if the primary spark generator fails during the course of an experiment. Last, the protocol described here involves the use of glass stopcocks, which require high vacuum grease to make appropriate seals. If desired, polytetrafluoroethylene (PTFE) stopcocks can be used to avoid vacuum grease. However, if examining these stopcocks for potential leaks with a spark leak detector, be cautious to not overexpose the PTFE to the spark as this can compromise the integrity of the PTFE and lead to poor seals being made by these stopcocks.

The significance of the method reported here with respect to existing techniques, lies within its simplicity. It uses a commercially available 3 L flask, which is also considerably less fragile and easier to clean between experiments than the original design used by Miller 5 . Because the apparatus is less cumbersome, it is small enough to carry out an experiment inside a fume hood.

Once the technique outlined here has been mastered, it can be modified in a variety of ways to simulate numerous types of primitive terrestrial environments. For example, more oxidized gas mixtures can be used 14,18,19 . Furthermore, using modifications of the apparatus, the energy source can be changed, for example, by using a silent discharge 4 , ultraviolet light 20 , simulating volcanic systems 4,12,21 , imitating radioactivity from Earth's crust 22 , and mimicking energy produced by shockwaves from meteoritic impacts 23 , and also cosmic radiation 18,19 .

The classic Miller-Urey experiment demonstrated that amino acids, important building blocks of biological proteins, can be synthesized using simple starting materials under simulated prebiotic terrestrial conditions. The excitation of gaseous molecules by electric discharge leads to the production of organic compounds, including amino acids, under such conditions. While amino acids are important for contemporary biology, the Miller-Urey experiment only provides one possible mechanism for their abiotic synthesis, and does not explain the origin of life, as the processes that give rise to living organisms were likely more complex than the formation of simple organic molecules.

Disclosures

The authors declare no competing financial interests.

Acknowledgments

This work was jointly supported by the NSF and NASA Astrobiology Program, under the NSF Center for Chemical Evolution, CHE-1004570, and the Goddard Center for Astrobiology. E.T.P. would like to acknowledge additional funding provided by the NASA Planetary Biology Internship Program. The authors also want to thank Dr. Asiri Galhena for invaluable help in setting up the initial laboratory facilities.

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March 28, 2007

Primordial Soup's On: Scientists Repeat Evolution's Most Famous Experiment

Their results could change the way we imagine life arose on early Earth

By Douglas Fox

A Frankensteinesque contraption of glass bulbs and crackling electrodes has produced yet another revelation about the origin of life.

The results suggest that Earth's early atmosphere could have produced chemicals necessary for life—contradicting the view that life's building blocks had to come from comets and meteors. "Maybe we're over-optimistic, but I think this is a paradigm shift," says chemist Jeffrey Bada, whose team performed the experiment at the Scripps Institution of Oceanography in La Jolla, Calif.

Bada was revisiting the famous experiment first done by his mentor, chemist Stanley Miller, at the University of Chicago in 1953. Miller, along with his colleague Harold Urey, used a sparking device to mimic a lightning storm on early Earth. Their experiment produced a brown broth rich in amino acids, the building blocks of proteins. The disclosure made the pages of national magazines and showed that theories about the origin of life could actually be tested in the laboratory.

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But the Miller-Urey results were later questioned: It turns out that the gases he used (a reactive mixture of methane and ammonia) did not exist in large amounts on early Earth. Scientists now believe the primeval atmosphere contained an inert mix of carbon dioxide and nitrogen—a change that made a world of difference.

When Miller repeated the experiment using the correct combo in 1983, the brown broth failed to materialize. Instead, the mix created a colorless brew, containing few amino acids. It seemed to refute a long-cherished icon of evolution—and creationists quickly seized on it as supposed evidence of evolution's wobbly foundations.

But Bada's repeat of the experiment—armed with a new insight—seems likely to turn the tables once again.

Bada discovered that the reactions were producing chemicals called nitrites, which destroy amino acids as quickly as they form. They were also turning the water acidic—which prevents amino acids from forming. Yet primitive Earth would have contained iron and carbonate minerals that neutralized nitrites and acids. So Bada added chemicals to the experiment to duplicate these functions. When he reran it, he still got the same watery liquid as Miller did in 1983, but this time it was chock-full of amino acids. Bada presented his results this week at the American Chemical Society annual meeting in Chicago.

"It's important work," says Christopher McKay, a planetary scientist at NASA Ames Research Center in Moffett Field, Calif. "This is a move toward more realism in terms of what the conditions were on early Earth."

Most researchers believe that the origin of life depended heavily on chemicals delivered to Earth by comets and meteorites. But if the new work holds up, it could tilt that equation, says Christopher Chyba, an astrobiologist at Princeton University. "That would be a terrific result for understanding the origin of life," he says, "and for understanding the prospects for life elsewhere."

But James Ferris, a prebiotic chemist at Rensselaer Polytechnic Institute in Troy, N.Y., doubts that atmospheric electricity could have been the only source of organic molecules. "You get a fair amount of amino acids," he says. "What you don't get are things like building blocks of nucleic acids." Meteors, comets or primordial ponds of hydrogen cyanide would still need to provide those molecules.

Bada's experiment could also have implications for life on Mars, because the Red Planet may have been swaddled in nitrogen and carbon dioxide early in its life. Bada intends to test this extrapolation by doing experiments with lower-pressure mixes of those gases.

Chyba is cautious: "We don't know," he says, "whether Mars really ever had that atmosphere." That's because Mars today has carbon dioxide, but hardly any nitrogen—which is also needed for making amino acids. Some scientists suspect that nitrogen gas existed on Mars, but was blasted away by asteroid impacts billions of years ago.

NOT EXACTLY ROCKET SCIENCE

Scientists finish a 53-year-old classic experiment on the origins of life

In 1958, a young scientist called Stanley Miller electrified a mixture of simple gases, designed to mimic the atmosphere of our primordial lifeless planet. It was a sequel to one of the most evocative experiments in history, one that Miller himself had carried five years earlier. But for some reason, he never finished his follow-up. He dutifully collected his samples and stored them in vials but, whether for ill health or dissatisfaction, he never analysed them.

The vials languished in obscurity, sitting unopened in a cardboard box in Miller’s office. But possessed by the meticulousness of a scientist, he never threw them away. In 1999, the vials changed owners. Miller had suffered a stroke and bequeathed his old equipment, archives and notebooks to Jeffrey Bada , one of his former students. Bada only twigged to the historical treasures that he had inherited in 2007. “Inside, were all these tiny glass vials carefully labeled, with page numbers referring Stanley’s laboratory notes. I was dumbstruck. We were looking at history,” he said in a New York Times interview .

By then, Miller was completely incapacitated. He died of heart failure shortly after, but his legacy continues. Bada’s own student Eric Parker has finally analysed Miller’s samples using modern technology and published the results, completing an experiment that began 53 years earlier.

Miller conducted his original 1953 experiment as a graduate student, working with his mentor Harold Urey. It was one of the first to tackle the seemingly insurmountable question of how life began. In their laboratory, the pair tried to recreate the conditions on early lifeless Earth, with an atmosphere full of simple gases and laced with lightning storms. They filled a flask with water, methane, ammonia and hydrogen and sent sparks of electricity through them.

The result, both literally and figuratively, was lightning in a bottle. When Miller looked at the samples from the flask, he found five different amino acids – the building blocks of proteins and essential components of life.

The relevance of these results to the origins of life is debatable, but there’s no denying their influence. They kicked off an entire field of research, graced the cover of Time magazine and made a celebrity of Miller. Nick Lane beautifully describes the reaction to the experiment in his book, Life Ascending : “Miller electrified a simple mixture of gases, and the basic building blocks of life all congealed out of the mix. It was as if they were waiting to be bidden into existence. Suddenly the origin of life looked easy.”

Over the next decade, Miller repeated his original experiment with several twists. He injected hot steam into the electrified chamber to simulate an erupting volcano, another mainstay of our primordial planet. The samples from this experiment were among the unexamined vials that Bada inherited. In 2008, Bada’s student Adam Johnson showed that the vials contained a wider range of amino acids than Miller had originally reported in 1953.

Miller also tweaked the gases in his electrified flasks. He tried the experiment again with two newcomers – hydrogen sulphide and carbon dioxide – joining ammonia and methane. It would be all too easy to repeat the same experiment now. But Parker and Bada wanted to look at the original samples that Miller had himself collected, if only for their “considerable historical interest”.

Using modern techniques, around a billion times more sensitive than those Miller would have used, Parker identified 23 different amino acids in the vials, far more than the five that Miller had originally described. Seven of these contained sulphur, which is either a first for science or old news, depending on how you look at it. Other scientists have since produced sulphurous amino acids in similar experiments, including Carl Sagan . But unbeknownst to all of them, Miller had beaten them to it by several years. He had even scooped himself – it took him till 1972 to publish results where he produced sulphur amino acids!

The amino acids in Miller’s vials all come in an equal mix of two forms, each the mirror image of the other. You only see that in laboratory reactions – in nature, amino acids come almost entirely in one version. As such, Parker, like Miller before him, was sure that the amino acids hadn’t come from a contaminating source, like a stray bacterium that had crept into the vials.

Imagine then, a young and violent planet, wracked with exploding volcanoes, noxious gases and lightning strikes. These ingredients combined to brew a “primordial soup”, fashioning the precursors of life in pools of water. On top of that, meteorites raining down from space could have added to the accumulating molecules. After all, Parker found that the amino acid cocktail in Miller’s samples is very similar to that found on the Murchison meteorite , which landed in Australia in 1969.

These are powerful images, so why aren’t people more excited? Echoing many sources I spoke to, Jim Kasting , who studies the evolution of Earth’s atmosphere, said, “I am underwhelmed by it.” The main problem with the study is that Miller was probably wrong about the conditions on early Earth.

By analysing ancient rocks, scientists have since found that Earth was never particularly teeming in hydrogen-rich gases like methane, hydrogen sulphide or hydrogen itself. If you repeat Miller’s experiment with a more realistic mixture – heavy in carbon dioxide and nitrogen, with just trace amounts of other gases – you’d have a hard time finding amino acids in the resulting brew.

Parker accepts the problem, but he suggests that a few specific places on the planet may have had the right conditions. Exploding volcanoes, for example, throw up masses of sulphurous compounds, as well as methane and ammonia. These gases, belched forth into lightning storms , could have produced amino acids that rained out and gathered in tidal pools. But Kasting still isn’t convinced. “Even then the reduced gases would not be as concentrated as they are in this experiment.”

Even if our young planet had the right conditions to produce amino acids, that’s a less impressive feat than it appeared in the 1950s. “Amino acids are old hat and are a million miles from life,” says Nick Lane. Indeed, as Miller’s experiments showed, it’s not difficult to create amino acids. The far bigger challenge is to create nucleic acids – the building blocks of molecules like RNA and DNA. The origin of life lies in the origin of these “replicators”, molecules that can make copies of themselves. Lane says, “Even if you can make amino acids (and nucleic acids) under soup conditions, it has little if any bearing on the origin of life.”

The problem is that replicators don’t spontaneously emerge from a mixture of their building blocks, just as you wouldn’t hope to build a car by throwing some parts into a swimming pool. Nucleic acids are innately “shy”. They need to be strong-armed into forming more complex molecules, and it’s unlikely that the odd bolt of lightning would have been enough. The molecules must have been concentrated in the same place, with a constant supply of energy and catalysts to speed things up. “Without that lot, life will never get started, and a soup can’t provide much if any of that,” says Lane.

Deep-sea vents are a better location for the origins of life. Deep under the ocean’s surface, these rocky chimneys spew out superheated water and hydrogen-rich gases. Their rocky structures contain a labyrinth of small compartments that could have concentrated life’s building blocks into dense crowds, and minerals that would have catalysed their get-togethers. Far away from visions of languid soups, these churning environments are the current best guess for the site of life’s hatchery.

So Miller’s iconic experiment, and its now-completed follow-ups, probably won’t lay out the first steps of life. As Adam Rutherford, who is writing a book on the origin of life, says, “It’s really a historical piece, like finding that Darwin had described a Velociraptor in one of his notebooks.”

If anything, the analysis of Miller’s vials is a testament to the value of meticulous scientific work. Here was a man who prepared his samples so cleanly, who recorded his notes so thoroughly, and who stored everything so carefully, that his contemporaries could pick up where he left off five decades later.

Reference: Parker, Cleaves, Dworkin, Glavin, Callahan, Aubrey, Lazcano & Bada. 2011. Primordial synthesis of amines and amino acids in a 1958 Miller H2S-rich spark discharge experiment. PNAS http://dx.doi.org/10.1073/pnas.1019191108

Photos by Carlos Gutierrez and Marco Fulle

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12th notes in hindi

मिलर सूचकांक की परिभाषा क्या है miller indices in hindi

(miller indices in hindi) मिलर सूचकांक की परिभाषा क्या है : क्रिस्टल में क्रिस्टल तलों व अभिविन्यासो को व्यक्त करने के लिए एक process का इस्तेमाल किया जाता है जिसे हम miller indices (मिलर सूचकांक) कहते हैं।

– माना क्रिस्टल की अक्ष a , b , c है , ये cell primitive या non primitive दोनों हो सकते है।

a , b , c अक्षो पर प्लेन द्वारा काटे गए inter shapy को lattice constant की फॉर्म में ज्ञात करते है।

माना lattice constant = p , q , r

– अंतखंड गुणांक p , q , r को व्युत्क्रम लिखने पर प्राप्त भिन्न को dominator (हर) का LCM लेते है।

इस LCM से सभी reciprocal (व्युत्क्रम) को गुणा कर सभी भिन्नो को पूर्णांकों में बदल देते है।

इस प्रकार प्राप्त किये गए क्रिस्टल तल को मिलर सूचकांक (miller indices) कहते हैं।

यदि miller indices ऋणात्मक आता है तो उन्हें बार (-) द्वारा प्रदर्शित करते है।

miller indices को (h,k,l) द्वारा प्रदर्शित किया जाता है।

मिलर सूचकांक (miller indices) के अभिलाक्षणिक गुण

IMAGES

(P-6) MILLER-UREY EXPERIMENT in Hindi/English| CLASS-12TH BIOLOGY
Stanley Miller Experiment in Hindi
स्टैनले मिलर का प्रयोग, Stanley miller experiment in Hindi, Evolution
Miller
स्टैनले मिलर का प्रयोग।। Stanley miller's experiment in Hindi।। Evolution chapter
Experiment of Stanley Miller Class 12th biology Hindi

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stanley miller ka prayog
स्टैनले मिलर का प्रयोग (Experiment of Stanley Miller)- ओपैरिन परिकल्पना के अनुसार प्रबल ...
Stanley Miller Experiment in Hindi
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स्टैनले मिलर का प्रयोग
you also search this topic- stanley miller experiment diagram urey miller experiment diagram miller's experiment class 12 diagram miller's experiment class 1...
स्टैनले मिलर का प्रयोग।। Stanley miller's experiment in Hindi
Hello doston is video mein maine aapko Stanley Miller ka prayog bataya hai. Stanley Miller ka prayog evolution chapter se liya gaya hai hai. yeah topic aapke...
मिलर के प्रयोग का वर्णन कीजिए तथा नामांकित चित्र
स्टेनले मिलर का प्रयोग (Stanley Miller's Experiment) - शिकागो विश्वविद्यालय के ...
Miller-Urey experiment
The Miller-Urey experiment was a synthesis of small organic molecules in a mixture of simple gases in a thermal gradient created by heating (right) and cooling (left) the mixture at the same time, with electrical discharges. The Miller-Urey experiment[ 1] (or Miller experiment[ 2]) was an experiment in chemical synthesis carried out in 1952 ...
Origin of Life:- Urey and Miller Experiment Part 2 (in Hindi).
Get access to the latest Origin of Life:- Urey and Miller Experiment Part 2 (in Hindi). prepared with CBSE Class 10 course curated by Savitree Singh on Unacademy to prepare for the toughest competitive exam.
PDF Miller Urey Experiment
orms of life on Earth.Miller-Urey experiment set-up, which simulates in the laboratory the coupled chemistry between the primitive Earth atmosphere (upper right bulb) and warm oc. ans (lower left bulb). In the first version, an atmosphere made of CH4, NH3, H2O, A spark discharge simulated storm lightning. to following reasons:CH4, NH3, H2O ...
Urey and Miller Experiment in Hindi
Watch Urey and Miller Experiment in Hindi from Origin of Life here. Watch all CBSE Class 5 to 12 Video Lectures here.
A Brief Explanation Of Miller Urey Experiment
Miller and Urey examined the cooled water after a week and observed that 10-15% of the carbon was in the form of organic compounds. 2% of carbon had formed 13 amino acids. Yet, the Miller and Urey experiments were condemned by their fellow scientists. Also read: Origin Of Life. Criticism of the Miller Urey Experiment
Miller-Urey Experiment
Miller-Urey Experiment. The Miller-Urey Experiment was a landmark experiment to investigate the chemical conditions that might have led to the origin of life on Earth. The scientist Stanley Miller, under the supervision of the Nobel laureate scientist Harold Urey conducted it in 1952 at the University of Chicago.
Describe the Miller's experiment related to origin of life.
Miller's experiment related to origin of life: In 1953, S.L. Miller, an American scientist created similar conditions in a laboratory scale. He created electric discharge in a closed flask containing C H 4, H 2, N H 3 and water vapour at 800 o C. He observed formation of amino acids. In similar experiments others observed, formation of sugars ...
Miller Urey Experiment: Hypothesis, Steps, Conclusions, and Limitations
The Miller-Urey experiment, conducted in 1953 by Stanley L. Miller and Harold C. Urey, aimed to simulate early Earth's conditions and test the Oparin-Haldane Hypothesis. Here are the key steps of the experiment: Simulating Early Earth's Atmosphere: The researchers recreated early Earth's atmosphere in a closed system using a mixture of ...
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About the video- स्टैनले मिलर का प्रयोग, Miller experiment, Miller ka prayog, मिलर का प्रयोग,#Miller_ka_prayog #bioaman #class12 # ...
Miller-Urey experiment
The Miller-Urey experiment was an experimental simulation conducted in 1953 that tested whether organic molecules could be formed from chemical reactions occurring between inorganic molecules thought to have been present early in Earth's history. To test Oparin and Haldane's ideas, Miller and Urey designed a closed experiment in a laboratory.
Explain the miller's experiment with the of diagram?
Analysis of the experiment was done by chromatography. At the end of one week, they observed that as much as 10-15% of the carbon was now in the form of organic compounds. Two per cent of the carbon had formed some of the amino acids which are used to make proteins. Thus this experiment showed that organic compounds such as amino acids, which ...
Conducting Miller-Urey Experiments
In 1952, Stanley Miller, then a graduate student at the University of Chicago, approached Harold Urey about doing an experiment to evaluate the possibility that organic compounds important for the origin of life may have been formed abiologically on the early Earth. The experiment was conducted using a custom-built glass apparatus ( Figure 1A ...
Prebiotic Soup--Revisiting the Miller Experiment
Apparatus used in the original Miller experiment. Open in viewer. Miller began the experiments in the fall of 1952. By comparison with contemporary analytical tools, the paper chromatography method available at the time was crude. Still, after only 2 days of sparking the gaseous mixture, Miller detected glycine in the flask containing water.
Primordial Soup's On: Scientists Repeat Evolution's Most Famous Experiment
When Miller repeated the experiment using the correct combo in 1983, the brown broth failed to materialize. Instead, the mix created a colorless brew, containing few amino acids.
Scientists finish a 53-year-old classic experiment on the origins of life
Miller conducted his original 1953 experiment as a graduate student, working with his mentor Harold Urey. It was one of the first to tackle the seemingly insurmountable question of how life began ...
Miller Urey Experiment Explained
Urey Miller Experiment | Experimenting First Stage of Origin | Info ReX with English subtitlesStanley L. Miller and Harold C. Urey performed an experiment to...
Miller Urey experiment in Hindi #shorts #short #education #gk
Miller Urey experiment in Hindi #shorts #short #education #gk #sciencefacts #khansir #shortsfeed#miller Urey ka experiment#experiment #experiment of miller Urey
मिलर सूचकांक की परिभाषा क्या है miller indices in hindi
मिलर सूचकांक की परिभाषा क्या है miller indices in hindi. Sbistudy April 22, 2018 chemistry. (miller indices in hindi) मिलर सूचकांक की परिभाषा क्या है : क्रिस्टल में क्रिस्टल तलों व ...

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