RIBONUCLEIC ACIDS 



carbon of one to the third carbon of the next (2 ',3' phospho- 

 diester Hnk), could not accommodate the facts which were 

 accumulating. Chief among these were the hydrolysis of RNA 

 to nucleosides and inorganic phosphate by snake venoms 

 (25-27) containing a phosphomonoesterase specific for 5' 

 nucleotides, and the reduction of periodate by the mixture of 



NH, 



NH, 



O O 



HO-P=0 



\ 



(a) 



W 



Fig. 1. Polynucleotide linkages: (a) section of 2 ',3' polynucleotide; (b) 



section of 3 ',5' polynucleotide. 



ribonuclease-produced polynucleotides after removal of end 

 phosphate groups by a phosphomonoesterase (54-56). The 

 venom experiments indicated that 5' nucleotides are present 

 in the course of the degradation by the mixture of enzymes 

 present in whole venom, and present to an extent approaching 

 the total nucleotide in the digest. Barring transphosphorylation, 

 this was evidence for a 2' (or 3') to 5' phosphate linkage. A 

 similar conclusion was warranted by the second observation 

 that ribonuclease produces polynucleotides, each one possessing 

 a monoesterified phosphate end group, which are susceptible 

 to periodate oxidation after removal of these end groups by a 

 monoesterase, and to a degree equivalent to the phosphate 

 removed. Since each such dephosphorylated polynucleotide 

 must retain one phosphate link to the adjacent nucleotide 



461 



