Amino acids

The history of amino acids begins four billion years ago. The Earth’s atmosphere then consisted of water vapour, carbon dioxide, nitrogen, carbon monoxide, hydrogen, methane and ammonia. It was hot, and for millions of years lightning flashes discharged a

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The history of amino acids begins four billion years ago. The Earth’s atmosphere then consisted of water vapour, carbon dioxide, nitrogen, carbon monoxide, hydrogen, methane and ammonia. It was hot, and for millions of years lightning flashes discharged across the sky (Fig. 4.1). Under these conditions initially ­aldehydes and hydrogen cyanide originated, and therefrom amino acids were produced (by Strecker reaction).

4.1  Electrostatic ­ discharges led to the first ­organic compounds.

Such a scenario was simulated in 1953 at the University of Chicago in legendary experiments by the young American chemist Stanley Lloyd Miller (1930–2007), who could recreate these processes in his laboratory within a week (Fig. 4.2). [1] Already in the first experiments he found glycine, alanine, β-alanine, aspartic acid and α-aminobutyric acid. [2] Miller’s reports caused a sensation – up until that time, it was believed, that the building stones of life could not emerge under “inorganic” conditions. Later it was discovered, that amino acids are even converted into short peptides by iron/nickel sulfides in the presence of carbon monoxide and hydrogen sulfide. [3, 4] B. Schaefer, Natural Products in the Chemical Industry, DOI 10.1007/978-3-642-54461-3_4, © Springer-Verlag Berlin Heidelberg 2014

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4  Amino acids

4.2  By using Stanley Miller’s apparatus, it became possible to prove that the building blocks of life had their origin in the prebiotic a ­ tmosphere.

Perhaps life also came out of the depths of the universe, in the form of c­ osmic dust or from meteorites. Following on from these first random dis­ coveries, by around 1970, astrophysicists began employing spectroscopic ­methods to search systematically for organic compounds in the huge inter­ stellar dust clouds. [5, 6] The result was overwhelming in terms of both, the number of compounds discovered (>170), and also their structure. By microwave spectroscopy of the dust clouds in the centre of our galaxy and in con­ stellations of Orion and Taurus (Taurus dark nebula) there were found, for example, common chemicals like ethanol, methanethiol, hydrogen cyanide, methyl formate, methylamine, formaldehyde and ketene, but also some extremely unusual compounds, such as 2,4,6-heptatriynonitrile or 2,4,6,8,10-undecapentaynonitrile (Fig. 4.3). [7] Interestingly enough, the Cassini-Huygens space probe revealed similar compounds also in our planetary neighbourhood, ­ itan. [8] In 2002, at the National Asin the athmosphere of Saturn’s moon T tronomy Observatory in Arizona, the first amino acid (glycine) was detected with a 12-metre telescope in the molecular clouds of Sagittarius B2 (the archer), Orion KL and W51, by observation of a characteristic set of 27 lines in the rotation/vibration spectrum. [9, 10] Even more convincing than the spectroscopic proof of amino acids in the universe is the chemical analysis of chondrites (meteorites). Seventeen amino acids were discovered in the Murchison chondrite, which was found in Australia; ten of these do not occur in Nature (on Earth