| Abstract
| - There is increasing interest in using nanopores in synthetic membranes as resistive-pulse sensorsfor molecular and macromolecule analytes. In general, this method entails measuring current pulsesassociated with translocation of the analyte through the nanopore sensor element. A key challenge for thissensing paradigm is building selectivity into the protocol so that the current pulses for the target analytecan be distinguished from current pulses for other species that might be present in the sample. We showhere that this can be accomplished with a protein analyte by adding to the solution an antibody that selectivelybinds the protein. We demonstrate this concept using bovine serum albumin (BSA) and a Fab fragmentfrom a BSA-binding polyclonal antibody. Because the complex formed upon binding of the Fab to BSA islarger than the free BSA molecule, the current-pulse signature for the BSA/Fab complex can be easilydistinguished from the free BSA. Furthermore, the BSA/Fab pulses can be easily distinguished from thepulses obtained for the free Fab and from pulses obtained for a control protein that does not bind to theFab. Finally, we also show that the current-pulse signature for the BSA/Fab complex can provide informationabout the size and stoichiometry of the complex.
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