title: Energy landscape of chelated uranyl: antibody interactions by dynamic force spectroscopy.
abstract: We used dynamic force spectroscopy (DFS) to explore the energy landscape of interactions between a chelated uranyl compound and a monoclonal antibody raised against the uranyl-dicarboxy-phenanthroline complex. We estimated the potential energy barrier widths and the relevant thermodynamic rate constants along the dissociation coordinate. Using atomic force microscopy, four different experimental setups with or without the uranyl ion in the chelate ligand, we have distinguished specific and nonspecific binding in the binding affinity of the uranyl compound to the antibody. The force loading rates for our system were measured from 15 to 26,400 pN/s. The results showed two regimes in the plot of the most probable unbinding force versus the logarithm of the loading rate, revealing the presence of two (at least) activation barriers. Analyses of DFS suggest parallel multivalent binding present in either regime. We have also built a molecular model for the variable fragment of the antibody and used computational graphics to dock the chelated uranyl ion into the binding pocket. The structural analysis led us to hypothesize that the two regimes originate from two interaction modes: the first one corresponds to an energy barrier with a very narrow width of 0.5 +/- 0.2 A, inferring dissociation of the uranyl ion from its first coordination shell (Asp residue); the second one with a broader energy barrier width (3.9 +/- 0.3 A) infers the entire chelate compound dissociated from the antibody. Our study highlights the sensitivity of DFS experiments to dissect protein-metal compound interactions.
authors: CEA Valrhô, Direction des Science du Vivant/Institut de Biologie environnementale et Biotechnologie/Service de Biochimie et Toxicologie Nucléaire, BP 17171, 30207 Bagnols sur Cèze, France.
authors: Michael
authors: M
authors: Odorico
authors: Jean-Marie
authors: JM
authors: Teulon
authors: Thérèse
authors: T
authors: Bessou
authors: Claude
authors: C
authors: Vidaud
authors: Laurent
authors: L
authors: Bellanger
authors: Shu-wen W
authors: SW
authors: Chen
authors: Eric
authors: E
authors: Quéméneur
authors: Pierre
authors: P
authors: Parot
authors: Jean-Luc
authors: JL
authors: Pellequer
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry*; D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D002614:Chelating Agents; D066298:In Vitro Techniques; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D010618:Phenanthrolines / Q000737:chemistry; D011487:Protein Conformation; D013816:Thermodynamics; D014501:Uranium / Q000737:chemistry*
chemical_list: D000911:Antibodies, Monoclonal; D002614:Chelating Agents; D010618:Phenanthrolines; D014501:Uranium