Anion exchange analysis of unmodified and phosphorothioate oligonucleotides

Oligonucleotide therapeutics employ phosphate backbone modifications to increase resistance towards nucleases, the most common being the replacement of the phosphodiester (PO) bond between single nucleotides by a phosphorothioate (PS) linkage. Phosphorothioate modified oligonucleotides potentially exhibit additional impurities, impacting on the physical properties of the molecule and separation by anion exchange chromatography (AEX). Tosoh Bioscience analyzes the differences of AEX analysis of an unmodified and a thioated oligonucleotide and shows how this method may be adjusted for modified oligonucleotides, using the TSKgel^® DNA-NPR column.