CHEMICAL BONDS IN NUCLEIC ACIDS 445 



dation of apurinic acid is that discussed above for structure XXXV, in 

 which fission at the broken Hne a o by an ehmination reaction or by hydroly- 

 sis is a major factor;- this mechanism would lead to products in which the 

 pyrimidine nucleoside residues retain phosphorus in excess of the mono- 

 nucleotide ratio (1:1), e.g., nucleoside diphosphates, dinucleoside triphos- 

 phates, etc. The low rate of dialysis of the pyrimidine-containing fragments 

 of Tamm et al}^^ against distilled water might be explained by the associa- 

 tion of low molecular weight with high ionic charge."* At present it is not 

 possible to resolve these matters, and further evidence bearing on nucleotide 

 sequence is required. 



