John J. Kasianowicz

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We show that an electric field can drive single-stranded RNA and DNA molecules through a 2.6-nm diameter ion channel in a lipid bilayer membrane. Because the channel diameter can accommodate only a single strand of RNA or DNA, each polymer traverses the membrane as an extended chain that partially blocks the channel. The passage of each molecule is detected(More)
Single molecules of DNA or RNA can be detected as they are driven through an alpha-hemolysin channel by an applied electric field. During translocation, nucleotides within the polynucleotide must pass through the channel pore in sequential, single-file order because the limiting diameter of the pore can accommodate only one strand of DNA or RNA at a time.(More)
Schacht (Schacht, J. (1976) J. Neurochem. 27, 1119-1124) demonstrated that neomycin, an aminoglycoside antibiotic, binds with high affinity to phosphatidylinositol 4,5-bisphosphate (PIP2). We investigated the binding of neomycin to PIP2 by making electrophoretic mobility measurements with multilamellar bilayer vesicles and surface potential measurements(More)
The alpha-hemolysin gene from Staphylococcus aureus, excluding the 5' region encoding the hydrophobic leader sequence, was amplified from genomic DNA. The identity of the disputed C terminus has been confirmed and revisions made to the internal sequence. The hemolysin is expressed at high levels in Escherichia coli and has been purified to homogeneity from(More)
To understand the mechanism by which individual DNA molecules enter nanometer-scale pores, we studied the concentration and voltage dependence of polynucleotide-induced ionic-current blockades of a single alpha-hemolysin ion channel. We find that the blockade frequency is proportional to the polymer concentration, that it increases exponentially with the(More)
Surface-tethered biomimetic bilayer membranes (tethered bilayer lipid membranes (tBLMs)) were formed on gold surfaces from phospholipids and a synthetic 1-thiahexa(ethylene oxide) lipid, WC14. They were characterized using electrochemical impedance spectroscopy, neutron reflection (NR), and Fourier-transform infrared reflection-absorption spectroscopy(More)
BACKGROUND There is a pressing need for new sensors that can detect a variety of analytes, ranging from simple ions to complex compounds and even microorganisms. The devices should offer sensitivity, speed, reversibility and selectivity. Given these criteria, protein pores, remodeled so that their transmembrane conductances are modulated by the association(More)
A simple carrier model describes adequately the transport of protons across lipid bilayer membranes by the weak acid S-13. We determined the adsorption coefficients of the anionic, A−, and neutral, HA, forms of the weak acid and the rate constants for the movement of A− and HA across the membrane by equilibrium dialysis, electrophoretic mobility, membrane(More)
Anthrax protective antigen (PA, 83 kDa), a pore-forming protein, upon protease activation to 63 kDa (PA(63)), translocates lethal factor (LF) and edema factor (EF) from endosomes into the cytosol of the cell. The relatively small size of the heptameric PA(63) pore (approximately 12 angstroms) raises questions as to how large molecules such as LF and EF can(More)
We demonstrate that a simple kinetic model describes the transport of protons across lipid bilayer membranes by the weak acid CCCP (carbonyl cyanidem-chlorophenylhydrazone). Four parameters characterize this model: the adsorption coefficients of the anionic and neutral forms of the weak acid onto the interface (β A andβ HA) and the rate constants for the(More)