Limits...
Direct electrical control of IgG conformation and functional activity at surfaces

View Article: PubMed Central - PubMed

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 Fab fragments exposed off an electrode surface. We demonstrate here that we can affect the conformation of IgGs, likely pushing/pulling electrostatically Fab fragments 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 Fab fragments 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.

No MeSH data available.


Representation of molecular arrangement and effect of substrate potential on the conformation and antigen binding ability of IgGs immobilized on Au electrodes.(a) A positive substrate potential repels IgGs’ positive charges (red dots) from the surface, pushing Fab fragments towards the solution bulk; antigen binding from solution is thus favored. (b) A negative substrate potential attracts IgGs’ positively charged residues, pulling Fab fragments towards the electrode surface; in this case, antigen binding is made less probable due to a decreased accessibility of specific recognition sites by antigens in solution. A uniform orientation of IgGs on the surface is achieved by the use of a His-tagged protein A layer, shown in the zoomed inset only, for the sake of clarity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5121884&req=5

f1: Representation of molecular arrangement and effect of substrate potential on the conformation and antigen binding ability of IgGs immobilized on Au electrodes.(a) A positive substrate potential repels IgGs’ positive charges (red dots) from the surface, pushing Fab fragments towards the solution bulk; antigen binding from solution is thus favored. (b) A negative substrate potential attracts IgGs’ positively charged residues, pulling Fab fragments towards the electrode surface; in this case, antigen binding is made less probable due to a decreased accessibility of specific recognition sites by antigens in solution. A uniform orientation of IgGs on the surface is achieved by the use of a His-tagged protein A layer, shown in the zoomed inset only, for the sake of clarity.

Mentions: Figure 1 anticipates the kind of molecular arrangement and operating principles for the direct electrochemical control of IgG conformation at an electrode surface.


Direct electrical control of IgG conformation and functional activity at surfaces
Representation of molecular arrangement and effect of substrate potential on the conformation and antigen binding ability of IgGs immobilized on Au electrodes.(a) A positive substrate potential repels IgGs’ positive charges (red dots) from the surface, pushing Fab fragments towards the solution bulk; antigen binding from solution is thus favored. (b) A negative substrate potential attracts IgGs’ positively charged residues, pulling Fab fragments towards the electrode surface; in this case, antigen binding is made less probable due to a decreased accessibility of specific recognition sites by antigens in solution. A uniform orientation of IgGs on the surface is achieved by the use of a His-tagged protein A layer, shown in the zoomed inset only, for the sake of clarity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121884&req=5

f1: Representation of molecular arrangement and effect of substrate potential on the conformation and antigen binding ability of IgGs immobilized on Au electrodes.(a) A positive substrate potential repels IgGs’ positive charges (red dots) from the surface, pushing Fab fragments towards the solution bulk; antigen binding from solution is thus favored. (b) A negative substrate potential attracts IgGs’ positively charged residues, pulling Fab fragments towards the electrode surface; in this case, antigen binding is made less probable due to a decreased accessibility of specific recognition sites by antigens in solution. A uniform orientation of IgGs on the surface is achieved by the use of a His-tagged protein A layer, shown in the zoomed inset only, for the sake of clarity.
Mentions: Figure 1 anticipates the kind of molecular arrangement and operating principles for the direct electrochemical control of IgG conformation at an electrode surface.

View Article: PubMed Central - PubMed

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 Fab fragments exposed off an electrode surface. We demonstrate here that we can affect the conformation of IgGs, likely pushing/pulling electrostatically Fab fragments 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 Fab fragments 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.

No MeSH data available.