ION-EXCHANGE CHROMATOGRAPHY 241 



from ribose-2- and 3-phosphates in a sulfate-plus-borate system (the borate 

 influences the position of the 3-phosphate only, as neither the 4- nor the 

 2- derivatives form complexes appreciably with borate). ^^ 



Ribose-1 -phosphate, in sulfate-borate systems, precedes only very 

 slightly ribose-3-phosphate.^' In the absence of borate, it would be expected 

 to precede ribose-4-phosphate. Its acid-labihty precludes its presence in 

 the acid hydrolysates used to produce the other four isomers, but we may 

 list the order of elution, in the sulfate-borate systems, as 4, 2, 1, 3, 5.^^ 



c. Nucleotides 



An extension of this method to the separation of cytidine-5'-phosphate 

 and deoxycytidine-5'-phosphate yields the expected result: the latter is not 

 complexed and thus precedes the ribose derivative (Fig. 25). This should 

 be applicable to all such pairs. 



V. Related Reviews 



The ion-exchange separation of the products of alkaline, diesterase and 

 nuclease digests of PNA and DNA, together with the methods of preparing 

 these digests, is described in a parallel review^* that includes the spectro- 

 photometric constants which are so useful in following the course of sepa- 

 ration. Detailed directions for the ion-exchange separation and concentra- 

 tion of the PNA and DNA mononucleotides are given elsewhere. ^^ 



^* W. E. Cohn, in Colowick and Kaplan, Methods in Enzymology, Vol. II, Academic 



Press, New York, in press. 

 "W. E. Cohn and J. X. Khym, also W. E. Cohn, E. Volkin and J. X. Khym, in 



W. W. Westerfeld, Biochemical Preparations, Vol. IV, John Wiley & Sons, New 



York, in press. 



