Table 3. Affinities (in nM) for PP7 coat protein of aptamers selected for binding from the N30 random sequence library.

RNA	Kd (nM)	No. of isolates
Aptamer A	0.7	2
Aptamer B	0.8	3
Aptamer C	1.0	4
Aptamer D	1.5	3
Aptamer E	2.0	16
Aptamer F	25	1
Aptamer G	2.0	2
Aptamer H	2.0	2
Others	80–700	7
PP7 WT	1.0

The number of occurrences of each aptamer are also indicated. The predicted secondary structures of these aptamers are shown in Figures 4 and 5. RNAs called ‘others’ represent sequences that turned out to have little affinity for coat protein.