||"The levels of spontaneous cleavage at three positions (site
1, A44 site 2, U91 site 3, A104) were quantitated and used
to estimate the apparent dissociation constant (KD) for
ligand binding (Fig. 4B). The KD value determined for
aptamer 1 alone (210 pM) is >10-fold better than the values
measured for other tight-binding riboswitch aptamers
(e.g., Winkler et al. 2002a, 2003 Mandal et al. 2003).
Similarly, the KD value for TPP binding by aptamer 2
(850 pM Fig. 4C) also represents one of the tightest
aptamer–metabolite interactions measured to date. These
findings support [researchers'] prediction that both B. anthracis tenA
aptamers sense TPP."