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Thermodynamic Analysis of Antigen–Antibody Binding Using Biosensor Measurements at Different Temperatures

1997; Elsevier BV; Volume: 246; Issue: 1 Linguagem: Inglês

10.1006/abio.1996.9999

1096-0309

Gabrielle Zeder‐Lutz, Emmanuel Zuber, Jean Witz, M.H.V. Van Regenmortel,

Monoclonal and Polyclonal Antibodies Research

The thermodynamic parameters of the interaction between hen egg white lysozyme and Fab D1.3 were determined by measuring the temperature dependence of the ratio of its kinetic association and dissociation rate constants. Biosensor technology (BIAcore 2000) was used to measure the rate constants at temperatures ranging from 5 to 40°C. The value of ΔG° at 25°C (−49 kJm−1) calculated by this method was very close to that obtained previously from fluorescence quenching measurements (−48.5 kJm−1). However, the value of ΔH° measured at 25°C by biosensor technology (−35 kJm−1) was smaller than that determined previously by microcalorimetry (−90 kJm−1). Another difference was the limited variation of lnKand ΔGwith temperature observed with BIAcore compared to the steady decrease of lnKwith temperature found by calorimetry. Our data showed that the binding reaction was driven only by enthalpy below 23°C, by enthalpy and entropy between 23 and 35°C, and only by entropy above 35°C. This suggests,inter alia,that the contribution from the enthalpy of hydration due to the water molecules present at the interface in the lysozyme–antibody complex is progressively eliminated as the temperature increases. Whereas calorimetric data pertain to all the components present in the sample, including solvent molecules, BIAcore measurements monitor only the physical association and dissociation of the two macromolecular species. The difference between the two sets of data may also reflect the complexity of the binding mechanism between lysozyme and Fab D1.3.