CHAl'. 32] THK ORIGIN OF LIFE 859 



If the peptide is desorbed from the mineral then the mineral is simply a catalyst, 

 and a catalyst cannot change the equilibrium constant of a reaction. 



In biological systems energy is "pumped" into the amino acids by adenosine 

 triphosphate. It seems clear that some method of "pumping energy" into the 

 amino acids is necessary in order to form peptides. 



There has been no synthesis of the purines and pyrimidines starting from the 

 constituents of the primitive atmosphere. However, adenine and possibly 

 guanine and uracil have been synthesized by allowing ammonium cyanide to 

 polymerize in aqueous solution (Oro, 1960; Oro and Kimball, 1961). Glycine, 

 alanine and aspartic acid are also formed by the polymerization of ammonium 

 cyanide (Oro and Kamat, 1961). Hydrogen cyanide is readily produced from 

 methane and ammonia (or nitrogen) by electric discharges and some other 

 sources of energy (Miller, 1955, 1957). However, these experiments were per- 

 formed in concentrated ammonium cyanide solutions (1.5 m) which could not 

 have been present on the primitive Earth. It has not been shown that such 

 reactions will take place in more dilute solutions. 



If the purine and pyrimidine bases and the sugar (ribose, deoxyribose or 

 other suitable sugar) are present then the problem of making a nucleotide or 

 adding phosphates to make a nucleotide is similar to making a ]3eptide bond. 

 Energy must be pumped into the system. The bases and sugar are less stable 

 than amino acids, so drastic treatments would not be effective here. 



If the nucleotides (in the di- or tri-phosphate form) can be made, then it 

 appears that their polymerization to polynucleotides should not be too difficult, 

 Ochoa has found an enzyme (Steiner and Beers, 1961) which will polymerize 

 ribonucleotide diphosphates and Kornberg (1960) has found an enzyme which 

 will polymerize the deoxyribonucleotide tri -phosphates. It is possible that 

 certain mineral surfaces might be able to accomplish this polymerization, or 

 enzymes might have developed by this time which could catalyze this re- 

 action. 



The synthesis of polypeptides with catalytic activity is an extremely difficult 

 one. Granick (1953) and Calvin (1956) have proposed that this synthesis 

 proceeded in steps. First a metal ion catalyzed a reaction, followed by the 

 formation of a chelate complex to give the metal greater activity. The next step 

 was the addition of a protein to give greater activity, followed by the "evolu- 

 tion" of this protein to improve on the catalytic activity and/or specificity. In 

 order for a molecule to evolve, there must be reproduction, mutation and selec- 

 tion. This process of molecular evolution could go on in an organism that could 

 reproduce, but one would think that the enzymes for a very primitive organism 

 would need some degree of specificity. If such molecular evolution took place 

 outside a living organism, then this hypothesis does not answer how such 

 primitive enzymes could have been reproduced so that there could be mutation 

 and selection. The problem might better be approached by looking for some 

 process for synthesizing enzymes that is more direct and does not require a 

 large degree of chance and evolution. 



