282 J. D. SMITH 



TABLE III 

 The Observed Electrophoretic Mobilities of Some Dinucleoside 

 Monophosphate Diesters and Similar Substances at pH 3.5 in 

 0.05 M Ammonium Formate Buffer^^. 2^ 



Observed movement in 0.05 M 

 ammonium formate buffer pH 3.5 

 Substance" (cm./2 hr. at -20 v. /cm.) 



A-p-A 4.2 



A-p-G 6.0 



A-p-C 2.0 



A-p-T 6.2 



G-p-C 3.0 



G-p-MC 3.0 



G-p-T 9.0 



C-p-C 



C-p-T 3.9 



T-p-T 10.9 



A-p-C-p-T 6.2 



A-p-MC-p-T 6.2 



" A, G, C, MC, and T represent deoxyadenosine, deoxyguanosine, deoxycytidine, deoxy-5-methylcytidine 

 and thymidine, respectively, and p represents a phosphate linking two nucleoside residues. 



c. Polynucleotides and Dinucleoside Monophosphates from Deoxyribonucleic 

 Acid 



Very similar techniques have been employed to isolate some of the poly- 

 nucleotides produced by the action of deoxyribonuclease on DNA.^^ A 

 combination of chromatography in solvent 1 and electrophoresis at pH 

 3.5 has been used to separate the dinucleoside monophosphates and analo- 

 gous compounds found in deoxyribonuclease digests which have been 

 treated with phosphomonoesterase.^^' 27 The principles of the electropho- 

 retic separation of these substances are similar to those for the separation 

 of polynucleotides. They contain one less primary and secondary dissoci- 

 ation per molecule than do the corresponding polynucleotides, and their 

 effective frictional resistances to motion are slightly different. The electro- 

 phoretic properties of some of these are given in Table III. 



d. Nucleoside Diphosphates 



The nucleoside diphosphates bear two primary and two secondary phos- 

 phate dissociating groups. At pH 7 and above they are the fastest-moving 

 nucleic acid components, while at pH 3.5 they are readily separated from 

 each other and from the corresponding mononucleotides as they bear an 

 additional negative charge due to the second primary phosphate group. 



26 J. D. Smith and R. Markham, Nature 170, 120 (1952). 



" J. D. Smith and R. Markham, Biochim. et Biophys. Acta 8, 350 (1952). 



