Miller’s experiment

Following Miller s experiment, many chemists successfully synthesized other compounds of biochemical relevance under prebiotic conditions - thereby demonstrating convincingly that several molecular bricks of life might have been present on prebiotic Earth. 

Munera [57] took into account both earth rotation and orbital motion, as a function of the local latitude and longitude. Prediction of the variation of speed difference as function of time of day are given in Munera [57] for the locations of Miller s experiment. The qualitative shape of the variations is of the same sort observed by Miller in the 1930s. However, the magnitudes are not correct because solar motion was not included.2 Selleri [58] allowed for small violations of Lorentz invariance a correction factor around 10-3 reproduces Miller s observations. Also independently, Allais [59] revisited Miller s work. He argues that Miller s seasonal variations are strong proof for a local anisotropy of space. 

Since HCN and aldehydes were produced directly from the electric discharge in the Miller s experiment [33], the Strecker reaction was very early proposed as a likely pathway for the prebiotic synthesis of amino acids. This reaction discovered in 1850 [34] is the most anciently known abiotic synthesis of a-amino acids, it originally consisted in the formation of an a-aminonitrile 1 from a carbonyl compound (either aldehyde or ketone), ammonia and hydrogen cyanide in moderately alkaline aqueous solution followed by aminonitrile hydrolysis in strong acid. 

Miller s experiments evaluated the effects of powder density, screw feed speed, roll speed, roll pressure, vacuum deaeration pressure, compaction rate, and... 

In the decades following Miller s experiment, many scientists repHcat-ed it, varied reactants, conditions, and energy sources, and have successfully produced amino acids and other important precursors. The energy sources in Miller s experiment (electric arcs and boiling water) were far too high to be realistic for the prebiotic Earth but were employed to make reactions occur in days rather than months or years. Eollowing decades of research, it is now understood that the great volcanic activity of the early planet would produce far more CO2, CO, and N2 than NH3, and CH4, Miller s precursors. Moreover, with no O2 and therefore no ozone (O3) in the atmosphere, intense UV radiation would decompose H2O to form radicals that destroy NH3 and convert CH4 to CO2 and... 

In the case of a few a-methylated amino acids (a-methyUsoleudne, isovaline, a-methylnorvaline), it is established, that an enantiomeric excess favours the (L)-enantiomer by up to 10%. [12-14] Obviously, enantiomerically enriched amino acids may also result under conditions in outer space (Fig. 4.4). This was surprising, since Miller s experiments always produced racemic amino acids. 

Cis-Trans Isomerism in Cycloalkanes A WORD ABOUT... Isomers—Possible and Impossible Summary of Isomerism Reactions of Alkanes A WORD ABOUT... Alternative Energy The Benefits of Hydrogen A WORD ABOUT... Methane, Marsh Gas, and Miller s Experiment... 

In the years since Miller s experiment, ideas about the chemistry of life s origin have become more precise as a consequence of much experimentation and of exploration in outer space. We now know that the earth s primary atmosphere was formed mainly by degassing the molten interior rather than by accretion from the solar nebula. It seems likely that the main carbon sources in the earth s early atmosphere were CO2 and CO, not methane as assumed by Miller, and that nitrogen was present mainly as N2 rather than as ammonia. Repetition of Miller-type experiments with these assumed primordial atmospheres again gave biomolecules. 

Miller s experiment provided a model for much work in the branch of a science now called chemical evolution or prebiotic chemistry, the study of chemical events that may have taken place on earth or elsewhere in the universe leading to the appearance of the first living cell. For additional reading, you can consult Chemical Evolution by Stephen F. Mason, Clarendon Press, Oxford, 1991. 

PAHs comprise a large percentage of the carbon found in interstellar space. They have even been observed in interstellar ice (Halley s comet, for example). It has been shown that ultraviolet irradiation of PAHs in ice produces aromatic ketones (Chapter 9), alcohols (Chapter 7), and other compounds, suggesting a role of PAHs in prebiotic chemistry (see A Word about Methane, Marsh Gas, and Miller s Experiment, page 60). 

Later, experimental examples that proved that the inverted region really exists were found (see Miller s experiment in Section 10.5.6). In addition, there was a theory that showed that the Rehm and Weller experiment does not disprove the Marcus inverted region. 

In spite of the above logical rationalization, the solution to the problem of purine synthesis came in a very roundabout way. You may say by serendipity. The initial spark emerged from a discussion between G. E. Hutchinson, from Yale, P. Abelson and myself (during the 1st International Oceanographic Congress held in New York in 1959) on the nature of the polymer formed by electrical discharges in Miller s experiment. Because of... 

The amino acids obtained from Miller s experiments were all racemic. Furthermore, only racemic amino acids were found on the Murchison meteorite which fell in Australia in 1969. This presents an interesting question How was optical activity introduced in complex molecules Among the various hypothesis, S. Akabori (46) proposed the following transformations for the synthesis of more complex polypeptides, which have been veri-... 

Stanley Miller at the University of Chicago more than 50 years ago. This experiment (in fact, of course, many were carried out prior to the successful one) is probably as well known as the Wohler synthesis of urea Miller s doctoral supervisor, Harold Urey (winner of the Nobel Prize in 1934), had suggested to Miller that he simulate a reducing primeval Earth atmosphere (as required by the Oparin-Haldane hypothesis) to electrical discharges and see what happens . Urey apparently expected that such an experiment would lead to a huge variety of organic compounds. 

New experiments using weakly reducing or neutral gas atmospheres were conceived and carried out more than 20 years after Miller s first successes (Schlesinger and Miller, 1983). Comparisons of a series of simulated prebiotic atmospheres containing CH4, CO and CO2 as carbon sources, using electrical discharges at 298 K, led to the following results ... 

Only a few years after the Miller-Urey experiment was published, J. Oro was able to synthesize one of the most important biomolecules, adenine. This purine derivative is not only a component of the nucleic acids, but as ATP, adenosine triphosphate (in combination with ribose and three phosphate residues), it plays a key role in the metabolism of all living creatures. The chemical formula of adenine is C5H5N5, or expressed in another way, (HCN)s. 

In all simulation experiments carried out under assumed prebiotic conditions, the question of possible concentrations in a primeval ocean arises 0.1 M solutions appear unrealistic, as this would correspond to about 12 g of amino acid per litre of seawater Miller s lagoons and Darwin s ponds then come to mind, i.e., the concentration of dilute solutions in small localized areas due to evaporation of water. Recently, the attention of scientists has shifted towards concentration processes occurring at the surface of minerals however, many of the problems involved remain unsolved. 

Much experience concerning the hydrogenation of conjugated dienes was obtained with butadiene hydrogenation. On Pt single crystals the reaction was found to be structure sensitive the activity sequence of different planes (marked with Miller s index) is... 

The field of the origin of life has progressed very much from the time of Stanley Miller s first experiment. However, the main hypothesis, that cellular life derives from inanimate matter, has not been demonstrated yet. It must then be considered still a working hypothesis. Not that we have alternatives within the realms of science, and I have outlined in Chapter 1 why divine creation cannot be considered as an alternative within science. Of course the question of God is not one that is solved in terms of rationality, but in terms of faith, and we are back to zero. 

Several authors have independently revisited Miller s work. Vigier s [7] interpretation was mentioned in Section I. In 1988 the present author began a revision of all experiments of the Michelson-Morley type (M-M experiments) reported in the literature. The review is published as Munera [57],... 

Telecon. Clark, C., PES, with Miller, S., Smurfit Newsprint. February 27, 1991. TDF experience. 

What leads a professional in the field to such a bleak view, especially after the progress in the heady days following Miller s trailblazing experiment It turns out that the successes, although real, paper over a plethora of problems that can only be appreciated when you move beyond the simple chemical production of some of the bare components of life. Let s look at a few of those problems. 

The experiment that Stanley Miller reported in 1952 stunned the world. As Miller has readily explained, however, that experiment was not the first such one he tried. Earlier he had set up his apparatus in a somewhat different manner and found that some oil was formed, but no amino acids. Since he thought amino acids would be the most interesting chemicals to find, he jiggled the apparatus around in hopes of producing them. Of course, if conditions on the ancient earth actually resembled Miller s unsuccessful attempts, then in reality no amino acids would have been produced. 

Thus, while macroscopically high acid concentrations did not influence Nyberg s experiments, one cannot easily dismiss possible effects from locally high concentrations near the anode. Values of pH in acetonitrile/water of about 2 are quite sufficient to bring about the acid-catalysed conversion of pentamethylbenzyl alcohol to its amide (Mayeda and Miller, 1972), and from what has been said earlier, this is the kind of pH that might prevail near the anode in a macroscopically neutral electrolyte solution. 

Figure 5.1 Stanley Miller s apparatus for the synthesis of organic compounds in abiotic conditions. Hydrogen cyanide, ammonia and amino acids are among the most interesting molecules which are obtained in this type of experiment.

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