title: Observation of Single-Protein and DNA Macromolecule Collisions on Ultramicroelectrodes.
abstract: Single-molecule detection is the ultimate sensitivity in analytical chemistry and has been largely unavailable in electrochemical analysis. Here, we demonstrate the feasibility of detecting electrochemically inactive single biomacromolecules, such as enzymes, antibodies, and DNA, by blocking a solution redox reaction when molecules adsorb and block electrode sites. By oxidizing a large concentration of potassium ferrocyanide on an ultramicroelectrode (UME, radius ≤150 nm), time-resolved, discrete adsorption events of antibodies, enzymes, DNA, and polystyrene nanospheres can be differentiated from the background by their "footprint". Further, by assuming that the mass transport of proteins to the electrode surface is controlled mainly by diffusion, a size estimate using the Stokes-Einstein relationship shows good agreement of electrochemical data with known protein sizes.
authors.affiliation: Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Jeffrey E
authors.initials: JE
authors.lastname: Dick
authors.affiliation: Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Christophe
authors.initials: C
authors.lastname: Renault
authors.affiliation: Center for Electrochemistry, Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States.
authors.forename: Allen J
authors.initials: AJ
authors.lastname: Bard
mesh_terms: D000327:Adsorption; D000818:Animals; D002374:Catalase / Q000737:chemistry; D002623:Chemistry Techniques, Analytical; D004247:DNA / Q000737:chemistry*; D004058:Diffusion; D004563:Electrochemistry / Q000379:methods; D004566:Electrodes; D005295:Ferrocyanides / Q000737:chemistry; D005949:Glucose Oxidase / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry; D007074:Immunoglobulin G / Q000737:chemistry; D046911:Macromolecular Substances; D051379:Mice; D054118:Nanospheres / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010957:Plasmids / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*
chemical_list: D005295:Ferrocyanides; D007074:Immunoglobulin G; D046911:Macromolecular Substances; D011137:Polystyrenes; D011506:Proteins; D004247:DNA; D005949:Glucose Oxidase; D006735:Horseradish Peroxidase; D002374:Catalase; C020354:hexacyanoferrate II; D010100:Oxygen