Relation between the activity of catalytic antibodies and the properties of substrates

The free energy of binding between catalytic antibodies and substrates is correlated with the properties of the substrates, both in the transition state (TS) and the ground state (GS). The free energy of binding was calculated from the kinetic parameters and four properties of the substrates; the solvent accessible surface area (SAS), enthalpy of hydration (ΔH), polarizability (α), and dipole moment (μ) were calculated using AM1. As a whole, TS shows a higher correlation than does GS, which is compatible with the fundamental concept of a catalytic antibody. Among these four properties, SAS gives the highest correlation coefficient (0.7616) while μ has a small correlation. Antibody-TS complexes seem to be stabilized by van der Waals force rather than a hydrophobic interaction.