Glycine prebiotic syntheses

Hydrogen cyanide and methanal are especially reasonable starting materials for the prebiotic synthesis of amino acids, purine and pyrimidine bases, ribose and other sugars. Formation of glycine, for example, could have occurred by a Strecker synthesis (Section 25-6), whereby ammonia adds to methanal in the... 

Electric discharges acting on a mixture of CO, N2, and H2 are not effective in amino acid synthesis unless the ratio of H2 to CO is greater than about 1.0. Glycine is produced in fair yield, but only small amounts of any higher amino acids are produced. Large amounts of formaldehyde are obtained, however, and formaldehyde is important in the prebiotic synthesis of sugars. 

Sidney Fox and Kaoru Harada, in particular, used simulation experiments to show how volcanism may have been involved in the synthesis of prebiotic molecules. They heated a stream of gas (CH4, NH3 and H2O) to about 1,123 K (using a silicate contact) after cooling, they could detect glycine, alanine, p-alanine and aspartic acid (among others). This experiment was intended to simulate exhalation from the earth s crust, as in volcanoes (Fox and Harada, 1961 Harada and Fox, 1964). 

As reminded by Lazcano and Miller [181], a possibility for the formation of prebiotic polymers is the spontaneous synthesis of a polymer from high-energy precursors. The direct polymerization of glycine nitrile into polyglycine [182-184] is sluggish, but it is thermodynamically favorable and the possibility of indirect catalytic processes remains to be explored. 

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