Biophysical Society Thematic Meeting - October 13-15, 2015

Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling

Wednesday Speaker Abstracts

Harnessing Antibodies at an Electrode Surface: Electrical Control of IgG Conformation and Functional Activity Paola Ghisellini 1 , Marialuisa Caiazzo 2,3 , Andrea Alessandrini 2,3 , Roberto Eggenhoeffner 1 , Massimo Vassalli 4 . Paolo Facci 4 . 4 National Research Council, Genova, Italy. 3 National Research Council, Modena, Italy, 1 University of Genova, Genova, Italy, 2 University of Modena and Reggio Emilia, Modena, Italy, We have devised a supramolecular edifice involving His-tagged protein A and antibodies to yield surface immobilized, uniformly oriented IgG layers with Fab fragments exposed off a gold electrode surface. We demonstrate here that we can affect the conformation of immobilized IgGs, likely pushing/pulling electrostatically Fab fragments towards/from the electrode surface. This result is achieved by the action of a potential applied to the electrode with respect to solution that acts on IgGs’ positively charged aminoacids (Lys and Arg). Such an action results, on its turn, in a modulation of the accessibility of the specific recognition regions of Fab fragments by antigens in solution. As a consequence, antibody binding affinity to antigens turns out to be affected by the sign of the applied potential: a positive potential, pushing Fab fragments towards solution, 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. A bunch of different yet concurrent experimental techniques has been used to measure binding kinetics and surface coverage, to evaluate the effect of the applied electric field on IgGs, and to point out the key role of positively charged residues in determining the phenomenon described here. Those techniques include EC-QCM, EIS, Fluorescence confocal microscopy and ECAFM. The reported findings expand the concept of electrical control on biological reactions and can be used to gate electrically specific recognition reactions with far reaching consequences in biosensors, bioactuators, smart biodevices, and nanomedicine in general [1].

References 1. P. Facci “Biomolecular Electronics: electrical control of biological systems and reactions” Elsevier, ISBN: 9781455731428, 2014.

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