Fig. 2.

Structure-switching DNA aptamers for potassium. Beginning with three previously studied aptamers that represent the predicted lower (TBA) and upper (20-10-5 and 19-11-3) limits of potassium binding, three additional sequences were created by either weakening the stem (predicted to decrease K_S) or strengthening the stem (predicted to increase K_S). These sequences are named using a code indicating the total number of nucleotides, nucleotides in the loop domain, and number of base pairs in the stem. For example 20-11-4-5′C contains 20 total nucleotides, 11 nucleotides in the loop domain, 4 base-pairs in the stem, and an unpaired cytosine residue on the 5′-end. Each sequence name is also color-coded to correlate with data presented throughout the paper.