476 Annals New York Academy of Sciences 



Middlebrook/^^ and by Akabori.^^^ This work has been reviewed recently'^*"^^^ 

 and has been extended by other workers. As a result of these investigations a 

 number of different pathways for the formation of polypeptides in a cosmic 

 body or on the primitive Earth seems possible. 



Polymers containing many of the amino acids found in proteins can be pre- 

 pared by heating a mixture of these amino acids in the presence of an excess of 

 dicarboxylic"'- ■^'^^ or diamine amino acids.^^^ This synthesis requires anhydrous 

 conditions and heating at high temperatures for relatively short periods of 

 time. 



The formation of homo- and heteropolypeptides can occur also under aqueous 

 conditions and at moderate temperatures, as shown by other workers. Thus, 

 unsubstituted amino acids'^' '^^^ and their corresponding amides^ *''^"'^^ and 

 nitriles'®^'^^'^^^ have been observed to polymerize directly, or by the action of 

 basic (ammonia) or surface (silicates) catalysts. 



A pathway which seems to be particularly good for the formation of poly- 

 peptides containing hydroxy acids is that of Akabori et al.,^^^ which is based 

 upon the condensation of aldehydes (also olefins) with polyglycine. The 

 natural occurrence of this process would be quite probable because, as has been 

 shown in our laboratory, polyglycines are readily formed from glycine in 

 aqueous ammonia systems. Furthermore, in practically all of the abiogenic 

 synthesis of amino acids studied, glycine has been found to be the predominant 

 amino acid formed. 



Another interesting pathway has been described recently by Schramm 

 et al™ Polyarginine (mol. wt. 4000 to 5000) was prepared from arginine 

 with the help of polyphosphate esters. Using the same method, polyleucine, 

 polyvaline, and polyserine were prepared in our laboratory. '^^ 



In addition to the above pathways of polypeptide formation other obser- 

 vations have been made which indicate that peptides or polymers containing 

 amino acids can also be obtained by the action of ultraviolet light^^- and 

 electric discharges."^ It should be added that some of the products obtained 

 by thermal polymerization have the ability to form microspheres with internal 

 structure,"* and of displaying some catalytic activity.^^^ 



Finally, a very significant recent development is the isolation of polymers 

 containing several amino acids from the reaction product of mixtures of hy- 

 drogen cyanide, ammonia, and water. ^'^ This is the same reaction mixture 

 that has been shown to give rise to the formation of amino acids, purines, purine 

 intermediates, and fluorescent pigments among other compounds. Because 

 nitriles are formed in this system it is possible that the above polymers result 

 from nitrile condensation reactions. Hydrogen cyanide has been suggested as 

 an amino acid condensing agent by Calvin."^ Hydrogen cyanide and also 

 cyanamide (formed by combination of CN and NHo radicals), were probably 

 abundant in the primordial cosmic bodies of the solar system. It is quite 

 possible that these reactants were responsible for the formation of a number of 

 polymeric compounds including polypeptides. In fact, it is known that un- 

 substituted cyanamide can be used for the synthesis of peptides."^ 



Synthesis of Polymicleotides 

 A possible abiogenic mechanism for the formation of a high energy phos- 

 phate compound, carbamyl phosphate, was proposed some time ago."^ F'orm- 



