Table 1.

Affinity constants K_a (× 10⁵ M⁻¹)^a corresponding to sensor titrations with various opiate guests.

Ka (× 105 M−1)
Guest	S1	S2	S3
Morphine	0.91	1.42	2.48
Heroin	6.40	7.13	7.01
Oxycodon	0.10	6.80	0.13
M3G	130	10.40	7.37
Normorphine	2.10	2.83	15.0
6-MAM	4.80	3.18	2.86

^aThe titrations recorded in H₂O (pH 3, HCl) and K_as are calculated based on the change in fluorescence intensity upon addition of each guest, using non-linear least-squares. All errors were < 15%.