The steady state at a pair of hemispherical microelectrodes

Alfred, Lake; Oldham, Keith B.

doi:10.1016/0022-0728(95)04067-x

Cited by 18 publications

(8 citation statements)

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“…[40][41][42] For example, it was shown that there is significant overlap between the steady-state diffusion layers at a pair of hemispherical microelectrodes when the center-center distance is less than 10 times of the electrode diameter. 41 By applying this simple criterion for the random array of the NPCs with the channel-channel distance of ∼150 nm, 43 the diffusion layer at each NPC overlaps when the channel diameter is larger than 15 nm. This value is in the range of the previously estimated values (10-40 nm) 7,43 while the central pore of the NPC is not disk-shaped; the pore has a length of ∼90 nm, is narrowest (40-50 nm in diameter) at the middle, and widens to ∼70 nm toward the cytoplasmic and nucleoplasmic periphery.…”

Section: Resultsmentioning

confidence: 99%

Permeability of the Nuclear Envelope at IsolatedXenopusOocyte Nuclei Studied by Scanning Electrochemical Microscopy

2005

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In interphase eukaryotic cells, molecular transport between the cytoplasm and the nucleus is mediated by the nuclear pore complex (NPC), which perforates the double-membraned nuclear envelope (NE). Local permeability of the NE at large intact nuclei (approximately 400 microm in diameter) isolated from Xenopus laevis oocytes was studied by scanning electrochemical microscopy (SECM). Steady-state tip current versus tip-nucleus distance curves (approach curves) were measured with 10- and 2-microm-diameter Pt disk microelectrodes at the nuclei in isotonic buffer solutions containing redox-active molecules. The approach curves in the normalized form are independent of the tip diameter, indicating diffusion-limited membrane transport of the redox molecules. SECM chronoamperometry demonstrated that a decrease in the steady-state tip current at short tip-nucleus distances is due to smaller diffusion coefficients and concentrations of the redox molecules in the nucleus than those in the buffer solution. The experimental approach curves fit very well with theoretical ones for freely permeable membranes, yielding the NE permeability to the molecules that is at least 2 orders of magnitude larger than permeability of bilayer lipid membranes and cell membranes. This result indicates that passive transport of the redox molecules across the NE is facilitated by open NPC pores. The flux of the redox molecules sustainable by a single NPC channel (>9.8 x 10(6) molecules per NPC per second) and the diameter of the channel pore (>15 nm) were estimated from the SECM data by assuming the NE as an array of nanometer-sized NPC pores. The effects of the redox molecules on the nucleus and the NPC function were examined by studying signal-mediated nuclear import of rhodamine-labeled bovine serum albumin with and without nuclear localization signals by fluorescence microscopy.

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Section: Resultsmentioning

confidence: 99%

Permeability of the Nuclear Envelope at IsolatedXenopusOocyte Nuclei Studied by Scanning Electrochemical Microscopy

2005

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“…The present paper is concerned with sphere caps and has no apparent relevance to conditions beyond point (d) on Figure , where the electrode has fully emerged from the insulating slab. It has recently been demonstrated that the steady-state current at such an electrode fits the equation exactly, and the empirical equation with an error less than 0.15%. The broken line in Figure was drawn with the help of (9.3).…”

Section: Caps Of Common Curvaturementioning

confidence: 88%

Steady-State Currents at Sphere-Cap Microelectrodes and Electrodes of Related Geometry

and

Oldham

1996

J. Phys. Chem.

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“…Saito proposed that the minimum separation between electrodes must be larger than 12 times the radius of the microdisk electrode (r c > 12r a ) 49 for purely radial diffusion in a microdisk array while Alfred and Oldham and Fletcher and Horne recommend r c > 20r a . 50,51 In both of experiments here, the pore-to-pore separation (r c ) is constant (r c = 310 μm) but the radii of the pores differ (r a = 26.5 or 11.5 μm). The ratio pore-to-pore separation/pore radius (r c /r a ) of the glass membranes is ∼12 and 27, both of which fulfill Saito's relation while only the side of the membrane exposing the smaller micropores (11.5 μm, laser exit side) meets the recommendation of Alfred and Oldham and Fletcher and Horne.…”

Section: Analytical Chemistrymentioning

confidence: 94%

An Electrochemical Sensing Platform Based on Liquid–Liquid Microinterface Arrays Formed in Laser-Ablated Glass Membranes

et al. 2016

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Arrays of microscale interfaces between two immiscible electrolyte solutions (μITIES) were formed using glass membranes perforated with microscale pores by laser ablation. Square arrays of 100 micropores in 130 μm thick borosilicate glass coverslips were functionalized with trichloro(1H,1H,2H,2H-perfluorooctyl)silane on one side, to render the surface hydrophobic and support the formation of aqueous-organic liquid-liquid microinterfaces. The pores show a conical shape, with larger radii at the laser entry side (26.5 μm) than at the laser exit side (11.5 μm). The modified surfaces were characterized by contact angle measurements and X-ray photoelectron spectroscopy. The organic phase was placed on the hydrophobic side of the membrane, enabling the array of μITIES to be located at either the wider or narrower pore mouth. The electrochemical behavior of the μITIES arrays were investigated by tetrapropylammonium ion transfer across water-1,6-dichlorohexane interfaces together with finite element computational simulations. The data suggest that the smallest microinterfaces (formed on the laser exit side) were located at the mouth of the pore in hemispherical geometry, while the larger microinterfaces (formed on the laser entry side) were flatter in shape but exhibited more instability due to the significant roughness of the glass around the pore mouths. The glass membrane-supported μITIES arrays presented here provide a new platform for chemical and biochemical sensing systems.

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The steady state at a pair of hemispherical microelectrodes

Cited by 18 publications

References 3 publications

Permeability of the Nuclear Envelope at IsolatedXenopusOocyte Nuclei Studied by Scanning Electrochemical Microscopy

Permeability of the Nuclear Envelope at IsolatedXenopusOocyte Nuclei Studied by Scanning Electrochemical Microscopy

Steady-State Currents at Sphere-Cap Microelectrodes and Electrodes of Related Geometry

An Electrochemical Sensing Platform Based on Liquid–Liquid Microinterface Arrays Formed in Laser-Ablated Glass Membranes

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