SELEX scheme for selecting high affinity aptamers.

<p>The target molecules and aptamer library are incubated and then partitioned to separate unbound and target-bound aptamers. Selected aptamers are amplified via polymerase chain reaction (PCR) to create an enriched pool for use in the next round of selection. Typically, 8–15 rounds of selection are required to isolate aptamers with high affinities. In our model, [<i>A_i</i>] denotes the concentration of unbound aptamers of type <i>i</i> and [<i>S</i>] denotes the concentration of unbound target molecules. The concentration of target-bound aptamers is denoted by [<i>A_iS</i>] for aptamers of type <i>i</i>.