236 WALDO E. COHN 



strongly sorbed rare earth ions more easily handled, so has it been found 

 that the complexes which sugars form with borate ion possess acidic prop- 

 erties of sufficient strength and of sufficiently differing quahties to permit 

 practical ion-exchange chromatography. 



Although the neutral sugars ribose and deoxyribose are seldom encoun- 

 tered in the usual nucleic acid digests, there exist other situations in nucleic 

 acid investigations (e.g., biosynthesis and precursor studies) in which it is 

 desirable to have at hand a method for the isolation of one or more sugar 

 components. The separation of a mixture of hexoses and pentoses on a 

 borate-anion exchanger with borate eluting solutions, as originally de- 

 veloped by Khym and Zill,"' " is shown in Fig. 19. Similar separations 

 have been demonstrated for specific groups of monosaccharides," for di-, 

 tri-, and tetrasaccharides,^^ and for sugar alcohols" (as well as the uronic 

 acids, which do not require borate for separation^). 



The dependence of these separations (i.e., of the distribution coefficients) 

 upon the strength of the borate complex and the dependence of this, in turn, 

 upon pH and the structural details of the sugars (e.g., cts-glycol groups, 

 furanoid or pyranoid forms, etc.) is discussed by Khym and Zill.^^ 



2. Sugar Phosphates (Borate in Solution Only) 



a. Nucleosides 



This method has been applied to the nucleosides by Jaenicke and von 

 DahP' and by Khym and Cohn^" (see Fig. 20). It is possible to increase 

 markedly the sorption of the ribonucleosides, whereupon such weakly 

 sorbed nucleosides as cytidine and adenosine become more strongly sorbed 

 and more easily separable. The difference between deoxynucleosidesand ribo- 

 nucleosides with respect to borate complex formation can be exploited to 

 facilitate their separation (see Fig. 21 in comparison to Fig. 4). 



h. Sugar Phosphates and the Isomeric Rihose Phosphates 



In the usual acid eluting system, the sugar monophosphates behave in 

 an almost identical fashion and are not well separated from one another. 

 The borate complexes, however, have made it possible to separate various 

 hexose phosphates from each other and from ribose-5-phosphate, the latter 

 being strongly affected by borate. The separation of a mix-ture of sugar 



6« J. X. Khym and L. P. Zill, J. Am. Chetn. Soc. 73, 2399 (1951). 

 --"J. X. Khym and L. P. Zill, /. Am. Chem. Soc. 74, 2090 (1952). 

 6« G. R. Noggle and L. P. Zill, Arch. Biochem. and Biophys. 41, 21 (1952). 

 " L. P. Zill, J. X. Khym, and G. M. Cheniae, J. Am. Chem. Soc. 75, 1339 (1953). 

 '8 J. X. Khym and D. G. Doherty, /. Am. Chem. Soc. 74, 3199 (1952). 

 " L. Jaenicke and K. von Dahl, N aturwissenschajten 39, 87 (1952). 



