Figure 1: Enrichment of unmodified RNA aptamer pool of 56 random nucleotides for binding with Stx2 through successive selection rounds of SELEX. Binding activity of the RNA pool was analyzed by filter binding assay. Strong enrichment of aptamer pool for Stx2-binders occurred at 5th round of selection by both m-SELEX (a) and p-SELEX (b) as 41% and 29% of the input RNA bound with Stx2, respectively, whereas binding to the membrane and unrelated protein BSA was <5%. The enrichment did not increase with additional rounds of selections. This experiment was repeated twice with similar results.