46 Life: Its Nature and Origin 



are the building blocks of protein, these results aroused great inter- 

 est in the question of the origin of life. Since Miller's historic ex- 

 periment, many amino acids have been synthesized by using various 

 mixtures of gases activated by electricity, ultra-violet irradiation, 

 and heat (Miller and Urey, 1959). It is therefore evident that 

 amino acids would have been formed by a variety of processes in 

 the reducing gas mixtures of the pre-biological world. 



Once formed, many of these products would have had a long 

 life. Abelson (1954) isolated amino acids from fossils up to 300 

 million years old and estimated that under today's climatic condi- 

 tions alanine would have a life of many billions of years. 



As Blum (1957) and Fox (1956) pointed out, it is a long step 

 from the production of amino acids to that of protein, and it is 

 protein which is practically synonymous with life. For amino acids 

 to polymerize into a protein-like chain, they must lose a molecule 

 of water at each linkage, and, outside biological systems, this loss 

 of water can be accomplished only by the addition of considerable 

 energy in a nearly anhydrous environment. Blum pointed out that 

 both Katchalski (1951) and Fox and Middlebrook (1954) had 

 achieved some success with protein synthesis under these hot dry 

 conditions. From this he suggested that, under pre-biological condi- 

 tions, pools containing dissolved amino acids might dry up, and in 

 this concentrated dry state, with the aid of solar energy, the amino 

 acids could have formed long polypeptides, that is, primeval pro- 

 teins. 



In later experiments Fox and Harada (1958) reported the pro- 

 duction of a true protein-like substance, called a proteinoid, by 

 heating mixtures of amino acids at temperatures of 170°C. These 

 proteinoids are split by proteolytic enzymes and have other prop- 

 erties of natural proteins. Fox and Harada also found that an excess 

 of aspartic and glutamic acids was necessary for the success of the 

 reaction, and that the addition of phosphoric acid increased the 

 yield. In the presence of a polyphosphoric acid, proteinoids resulted 

 from mixtures of 15 amino acids at temperatures as low as 70°C 

 (Fox, 1960). One of their proteinoids had a mean chain weight 

 of 4,900, and the proteinoids as a whole contained residues of 18 

 amino acids. A large number of different non-random combinations 

 were obtained. 



When hot saturated solutions of these proteinoids cool, they 

 form huge numbers of uniform, microscopic elastic spherules ( Fig. 

 20 ) ( Fox, Harada, and Kendrick, 1959 ) . At room temperature these 



