title: Thermodynamic studies on the interaction of antibodies with beta-amyloid peptide.
abstract: Antibodies against beta-amyloid peptides (Abetas) are considered an important therapeutic opportunity in Alzheimer's disease. Despite the vast interest in Abeta no thermodynamic data on the interaction of antibodies with Abeta are available as yet. In the present study we use isothermal titration calorimetry (ITC) and surface plasmon resonance to provide a quantitative thermodynamic analysis of the interaction between soluble monomeric Abeta(1-40) and mouse monoclonal antibodies (mAb). Using four different antibodies directed against the N-terminal, middle, and C-terminal Abeta epitopes, we measured the thermodynamic parameters for the binding to Abeta. Each antibody species was found to have two independent and equal binding sites for Abeta with binding constants in the range of 10(7) to 10(8) M(-1). The binding reaction was essentially enthalpy driven with a reaction enthalpy of DeltaH(0)(Abeta) approximately -19 to -8 kcal/mol, indicating the formation of tight complexes. The loss in conformational freedom was supported by negative values for the reaction entropy DeltaS(0)(Abeta). We also measured the heat capacity change of the 1mAb:2Abeta reaction. DeltaC(0)(p, abeta) was large and negative but could not be explained exclusively by the hydrophobic effect. The free energy of binding was found to be linearly correlated with the size of the epitope.
authors.affiliation: Department PRBD, F. Hoffmann-La Roche Ltd., CH-4070 Basel, Switzerland, and Department of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.
authors.forename: Manfred
authors.initials: M
authors.lastname: Brockhaus
authors.forename: Peter
authors.initials: P
authors.lastname: Ganz
authors.forename: Walter
authors.initials: W
authors.lastname: Huber
authors.forename: Bernd
authors.initials: B
authors.lastname: Bohrmann
authors.forename: Hans-Ruedi
authors.initials: HR
authors.lastname: Loetscher
authors.forename: Joachim
authors.initials: J
authors.lastname: Seelig
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry*; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D002151:Calorimetry / Q000379:methods; D012680:Sensitivity and Specificity; D012995:Solubility; D013329:Structure-Activity Relationship; D020349:Surface Plasmon Resonance / Q000379:methods; D013696:Temperature; D013816:Thermodynamics
chemical_list: D016229:Amyloid beta-Peptides; D000911:Antibodies, Monoclonal