General method for kinetic and thermodynamic evaluation of a receptor model peptide-drug molecule interaction studied by surface plasmon resonance

Abstract This work presents a detailed description of a commonly used and low-cost evaluation process that is simply based on the nonlinear fitting of concentration-, time- and temperature-dependent surface plasmon resonance (SPR) sensorgrams in order to provide kinetic and thermodynamic characterization of a biologically relevant interaction. Regardless of type, this evaluation proceeding is maximally suitable to manage the time-dependent sensor signals of other quasi two-dimensional sensor techniques, like quartz crystal microbalance (QCM) or optical waveguide lightmode spectroscopy (OWLS). Based on the hypothetic reaction schemes, the SPR signals have been fitted by the analytical solutions of the rate equations using optional spreadsheet software. Statistical tests of the goodness of nonlinear fits confirm the application of a reversible, pseudo first order kinetic model, in this way the apparent ( k obs ), the association ( k a ) and the dissociation ( k d ) constants as well as the equilibrium constants ( K A ) and the Gibbs free energy change ( ΔG ) have been calculated at six different temperatures. The enthalpy ( ΔH 0 ), entropy ( ΔS 0 ) and heat capacity changes ( ΔC p ) have also been estimated using nonlinear regression analysis. The sign and values of the state functions approve the presence of a salt bridge between a model polypeptide fragment of human glutamate receptor (ANYT) and kynurenic acid (KYNA) which was confirmed by molecular docking calculations as well.