SYNTHESIS OF BLOCK OLIGONUCLEOTIDES.

The concentration of sodium chloride strongly influences primed polymerization of nucleoside diphosphates by polynucleotide phosphorylase. High concentrations of NaCl allow the addition of only a few nucleotide residues onto the 3' end of the primer. When pure oligonucleotides are used as primers and when the product is fractionated, pure block oligonucleotides can be obtained.