title: Selective dynamic concentration of peptides at poles of cation-selective nanoporous granules.
abstract: The authors exposed a non-equilibrium dynamic counterion and coion analyte concentration to an AC electric field to selectively concentrate peptides at the poles of a cation-selective granule. The counterion polarization results from the focusing of the electric field show a discontinuous drop in the intra-granule counterion electromigration flux at the pole. The coion concentration polarization is due to the combined external convective and electromigration fluxes toward the pole that neutralize the accumulating counterions. Because the electromigration mobility of the peptide anion analyte depends on the pH, the authors determined a 20 000-fold high concentration factor for a near-neutral pH of 6.0 to 7.7. Because the peptide is protonated at the acidic pole and its absolute charge ranges from -0.3 to -1.9, the concentration factor scales exponentially with the absolute charge, thus allowing extremely selective concentrations of various peptides, which is demonstrated by fluorescein isothiocyanate tagged angiotensin I (pI ∼ 5.8) and Texas red tagged avidin (pI ∼ 10.5). This dynamic concentration effect can substantially enhance the sensitivity of bio-assays.
authors.affiliation: Department of Chemistry and Biochemistry and the Center for Nano Bio-detection Technologies, National Chung Cheng University, Chia-Yi 621, Taiwan.
authors.forename: Hsiao-Ping
authors.initials: HP
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Biochemistry and the Center for Nano Bio-detection Technologies, National Chung Cheng University, Chia-Yi 621, Taiwan.
authors.forename: Chia-Chun
authors.initials: CC
authors.lastname: Tsai
authors.affiliation: Department of Chemistry and Biochemistry and the Center for Nano Bio-detection Technologies, National Chung Cheng University, Chia-Yi 621, Taiwan.
authors.forename: Hung-Meng
authors.initials: HM
authors.lastname: Lee
authors.affiliation: Department of Chemistry and Biochemistry and the Center for Nano Bio-detection Technologies, National Chung Cheng University, Chia-Yi 621, Taiwan.
authors.forename: Shau-Chun
authors.initials: SC
authors.lastname: Wang
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Hsueh-Chia
authors.initials: HC
authors.lastname: Chang