Recovery of an oligonucleotide using silver ions immobilized onto paramagnetic particles

A 3'-GCCCCTTTTTAAAAACCCCG-5' oligonucleotide can be recovered from aqueous solution using paramagnetic particles containing immobilized silver ions. Binding and elution experiments were conducted by attaching either fluorescein isothioocyanate (FITC) to the 3'-end or Texas Red or fluorescein phosphoramidite (FAM) to the 5'-end of the oligonucleotide. For the 5'-end FAM labeled oligonucleotide, a binding constant of 4.2 x 10⁷ was measured at pH 7 using phosphate buffer. The percent of bound FAM labeled oligonucleotide eluted from the paramagnetic particles was found to be 97% using an aqueous solution of thiodiglycol. While the FAM molecule by itself does not bind to the silver activated paramagnetic particles, the choice of fluorescent label affects binding affinities and elution recoveries.