In nature, human serum albumin (HSA) has been reported to have a binding pocket for capturing OTA. It is composed of basic residues, including tryptophan (Trp) and arginine (Arg), and hydrophobic residues such as valine (Val). Since the first reported solid-state peptide synthesis, extensive research has greatly expanded the peptide library. An appropriate synthetic peptide with the aforementioned residues would enable efficient capture of OTA even in non-aqueous solutions without the effect of denaturation-induced deactivation. Among the peptides available with Trp, Arg, and Val, we selected leuprorelin (1, Fig. ), a peptide comprising nine residues, as the binding model for efficient capture of OTA. 1 has a tyrosine (Tyr) unit, which is promising for anchoring the peptide to a porous resin through a covalently linked ether bridge formed by the SN2 reaction of phenolic hydroxyl groups. To understand the molecular association in a homogeneous system, we first carried out spectroscopic analyses of an OTA solution in the presence of 1 at various concentrations. As shown in Fig. , the pristine OTA solution in acetonitrile showed emission in the visible with a maximum at 451nm (purple line), while the addition of 1 shifted the peak maxima to 465 nm (red line) with two "isosbestic" points at 399 and 431 nm. The presence of isosbestic points suggests a possible equilibrium between free OTA and the OTA/1 complex without any other species involved in the equilibrium. It is noteworthy that spectroscopic changes occurred even at low concentrations (25 nM for OTA and 0.1-1.6 μM for 1). The enhanced emission is due to the structural change of OTA and/or the change in the dielectric constant of the surrounding environment from polar acetonitrile to the less polar peptide scaffold, which increases the transition probability in the radiative decay of a singlet excited state upon association with 1. This also supports the strong interaction and complexation of the OTA/1 pair. The Hill plot of the obtained spectroscopic results predicted 1:1 complexation (Fig. ) with a slope of ca. 1 and a correlation coefficient (R 2 ) of 0.986, while the Benesi-Hildebrand plot 47 based on Eq. 1 (1) gave an equilibrium constant of 4.0 × 10 6 M -1 at 297 K (Fig. ). In Eq. 1, [OTA] is the initial concentration of OTA, FL is the difference in the emission intensity of OTA at a specified wavelength upon the addition of 1, K is the binding constant in M -1 , [1] is the concentration of added 1, and (ceq -c0) -1 is a constant (for a detailed derivation of the Hill equation and Benesi-Hildebrand equation, see ESI † ).