To create an asymmetric binding pocket within TTR, we capitalized on the wellcharacterized dissociative equilibrium of TTR between its tetrameric and monomeric forms. Mixed TTR tetramers can been generated by mixing an equimolar concentration of WT TTR□ homotetramers and A108G TTR■ homotetramers to give a statistical distribution of mixed interfaces (1:2:1 TTR□/TTR□ : TTR□/TTR■ : TTR■/TTR■). Thus, an asymmetric interface designed to bind 5 or 3 could be realized (Fig. ) In a similar manner as for 4 described above (Fig. ), 5 and 3 were anticipated to produce enol emission in bulk solution but elicit keto emission upon specific binding to the asymmetric TTR□/TTR■ interface. Following this logic, asymmetric TTR□/TTR■ interfaces were generated by allowing a 5.0 μM solution of WT TTR□ and A108G TTR■ to equilibrate at 25 o C for seven days. Probes 5 and 3 were then administered (Fig. ).