title: Direct electrical control of IgG conformation and functional activity at surfaces.
abstract: We have devised a supramolecular edifice involving His-tagged protein A and antibodies to yield surface immobilized, uniformly oriented, IgG-type, antibody layers with Fabfragments exposed off an electrode surface. We demonstrate here that we can affect the conformation of IgGs, likely pushing/pulling electrostatically Fabfragments towards/from the electrode surface. A potential difference between electrode and solution acts on IgGs' charged aminoacids modulating the accessibility of the specific recognition regions of Fabfragments by antigens in solution. Consequently, antibody-antigen affinity is affected by the sign of the applied potential: a positive potential enables an effective capture of antigens; a negative one pulls the fragments towards the electrode, where steric hindrance caused by neighboring molecules largely hampers the capture of antigens. Different experimental techniques (electrochemical quartz crystal microbalance, electrochemical impedance spectroscopy, fluorescence confocal microscopy and electrochemical atomic force spectroscopy) were used to evaluate binding kinetics, surface coverage, effect of the applied electric field on IgGs, and role of charged residues on the phenomenon described. These findings expand the concept of electrical control of biological reactions and can be used to gate electrically specific recognition reactions with impact in biosensors, bioactuators, smart biodevices, nanomedicine, and fundamental studies related to chemical reaction kinetics.
authors.affiliation: Department of Surgical Sciences and Integrated Diagnostics, University of Genova, Corso Europa 30, 16132 Genova, Italy.|Interuniversity Consortium INBB-Viale delle Medaglie d'Oro, 305, 00136 Roma, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Ghisellini
authors.affiliation: Department of Physical, Informatic and Mathematical Sciences, University of Modena and Reggio Emilia, Via G. Campi 213/A, 41125 Modena, Italy.|CNR-Nanoscience Institute-S3, Via G. Campi 213/A, 41125 Modena, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Caiazzo
authors.affiliation: Department of Physical, Informatic and Mathematical Sciences, University of Modena and Reggio Emilia, Via G. Campi 213/A, 41125 Modena, Italy.|CNR-Nanoscience Institute-S3, Via G. Campi 213/A, 41125 Modena, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Alessandrini
authors.affiliation: Department of Surgical Sciences and Integrated Diagnostics, University of Genova, Corso Europa 30, 16132 Genova, Italy.|Interuniversity Consortium INBB-Viale delle Medaglie d'Oro, 305, 00136 Roma, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Eggenhöffner
authors.affiliation: CNR-IBF, Via De Marini, 6, 16149 Genova, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Vassalli
authors.affiliation: CNR-IBF, Via De Marini, 6, 16149 Genova, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Facci
mesh_terms: D000906:Antibodies / Q000737:chemistry; D000941:Antigens / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods; D004560:Electricity; D004566:Electrodes; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry; D007074:Immunoglobulin G / Q000737:chemistry*; D008968:Molecular Conformation; D013057:Spectrum Analysis / Q000379:methods; D013205:Staphylococcal Protein A / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000906:Antibodies; D000941:Antigens; D007140:Immunoglobulin Fab Fragments; D007074:Immunoglobulin G; D013205:Staphylococcal Protein A