Figure 2.

Natural and unnatural base pairs for UB-DNA aptamer generation and anti-DEN-NS1 UB-DNA aptamers. (a) Chemical structures of the natural base pairs, A–T and G–C, and the unnatural base pairs, Ds–Px and Ds–Pa. (b) Presumed secondary structures of UB-DNA aptamers that bind specifically to each serotype DEN-NS1: AptD1 to DEN1-NS1, AptD2 to DEN2-NS1, AptD3 to DEN3-NS1, and AptD4 to DEN4-NS1. Each aptamer’s dissociation constant (K_D) determined by SPR analysis is shown. The unnatural Ds and Pa bases are shown in yellow and pink circles. At each aptamer’s 3′-terminus, the stable mini-hairpin sequence (CGCG(Bio-T)AGCG) is attached for stabilization against heat and nucleases and to introduce the biotinylated T (Bio-T) for aptamer immobilization.