31. SYNTHESIS OF POLYNUCLEOTIDES 



107 



cleotide linkage is designated by a method analogous to that already in 

 use for the specification of oligosaccharides. The name of each nucleotide 

 residue is followed by two numbers, separated by an arrow, in parentheses 

 inserted into the name by hyphens. The first number refers to the carbon 

 atom by which the phosphodiester is joined to the preceding nucleoside. 

 The second number denotes the point of linkage to the succeeding nucleo- 

 side. The use of the system is illustrated in the examples given below. Ob- 

 viously, the system permits equally well the naming of a polynucleotide 

 chain in one or the other direction and for maximum simplicity the choice 

 of naming may be influenced by the nature of the groups present at one or 

 the other terminus of the chain. 



A further modification may be introduced in that the terminal nucleotide, 

 bearing the phosphomonoester group or a 2',3'-cyclic phosphate group in 

 the ribopolynucleotide series may be designated, e.g., as nucleoside-5'- 

 phosphate or nucleoside-2' , 3 '-cyclic phosphate (see Examples 1, 2, and 3). 



Example 1 



Structure 



Diagrammatic representation Abbreviation 



O 



II 

 HO— POCj 



OH 



Cytosine 



CAT 



Adenine 



J \ 



d-pCpApT 



Thymine 



OH 



Full names: 5'-0-Phosphoryl-deoxycytidylyl-(3' — > 5')-deoxyadenylyl-(3' — » 5')- 

 thymidine 



or 

 Thymidylyl-(5' — » 3')-deoxyadenylyl-(5' — > 3')-deoxycytidylic-(5') acid 



or 

 Thymidylyl-(5' — » 3')-deoxyadenylyl-(5' — » 3')-deoxycytidine-5' phos- 

 phate 



