Ara h 1 protein-antibody dissociation study: evidence for binding inhomogeneities on a molecular scale

The characterization of biomolecular interactions is essential when designing novel biosensors, since the interaction between the bioreceptor and the ligand determines important biosensing parameters such as sensitivity and selectivity. In this paper we study the interaction of the trimeric Ara h 1 protein with a monoclonal anti-Ara h 1 antibody by means of magnetic force-induced dissociation. The proteins were bound to magnetic particles and polystyrene surfaces by EDC/NHS reaction chemistry and by physisorption, respectively. Two different molecular configurations have been investigated, with either the Ara h 1 protein on the particles or the Ara h 1 protein on the polystyrene surface. A model with a Gaussian distribution of energy barriers for dissociation gives an adequate description for the measured multi-exponential decays. We hypothesize that distributions of molecular orientations as well as experimentally induced variations may underlay the observed distributions. The two molecular configurations show a different peak value of the energy distribution. Similarly, SPR experiments for two distinct configurations (either Ara h 1 protein on the surface, or anti-Ara h 1 antibody on the surface) also show clear differences in dissociation behavior. We hypothesize that the multivalency of the involved molecules leads to different modes of binding. The results of this work highlight the importance of molecular inhomogeneities when studying the interaction processes of biomolecular complexes.