Fig. 2.
Secondary structures for the 27-base RNA models of the 16S and 18S A-sites. U1406 of the 16S A-site is replaced with an isosteric emissive nucleoside analogue as a donor (F1); the place-holding molecule is tagged with an appropriate fluorophore (F2); the 18S A-site is tagged with an acceptor (F3) to match the labeled “place-holder” (F2). The affinity and selectivity of unlabeled small-molecules for either A-sites can be accurately monitored using FRET, as the place-holder is displaced.
