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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.