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Conduction and blocking properties of a predominantly anion-selective channel from human platelet surface membrane reconstituted into planar phospholipid bilayers (1989)

Manning, S. D. ; Williams, A. J.

Springer

The journal of membrane biology 109 (1989), S. 113-122

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ISSN: 1432-1424

Keywords: platelet surface membrane ; lipid bilayer ; anion channel ; ion selectivity ; block

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary We have investigated the basic properties of a predominantly anion-selective channel derived from highly purified human platelet surface membrane. Single channels have been reconstituted into planar phospholipid bilayers by fusion of membrane vesicles and recorded under voltage-clamp conditions. The channel is found to have the following properties: (i) Channel activity occurs in bursts of openings separated by long closed periods. (ii) The current-voltage relationship is nonlinear. Channel current is seen to rectify, with less current flowing at positive than at negative voltages. Rectification may be due to asymmetric block by HEPES/Tris buffers. In 450mm KCl, 5mm HEPES/Tris, pH 7.2 the single channel conductance at −40 mV is ∼160 pS and at +40 mV is ∼90 pS. (iii) The conductanceconcentration relationship follows a simple saturation curve. Half maximal conductance is achieved at a concentration of ∼1000mm KCl, and the curve saturates at a conductance of ∼500 pS. (iv) Reversal potentials interpreted in terms of the Goldman-Hodgkin-Katz equation indicate a Cl∶K permeability ratio of 4∶1. (v) The channel accepts all of the halides as well as a number of other anions. The following sequence of relative anion permeabilities (in the presence of K+) is obtained: F−〈acetate−〈gluconate−〈Cl−〈Br−〈I−〈NO 3 − 〈SCN−. (vi) Cations as large as TEA+ are permeant. (vii) Current through the channel is blocked in the presence of DIDS, SITS and ATP, but not by Zn2+.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01870850

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Supercritical fluid extraction / capillary supercritical fluid chromatography / Fourier transform infrared microspectrometry of polycyclic aromatic compounds in a coal tar pitch (1988)

Raynor, M. W. ; Davies, I. L. ; Bartle, K. D. ; [et al.]

Weinheim : Wiley-Blackwell

Journal of High Resolution Chromatography 11 (1988), S. 766-775

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ISSN: 0935-6304

Keywords: Supercritical fluid extraction, SFE ; Supercritical fluid chromatography, SFC ; Fourier transform infrared microspectrometry, FTIR ; Narrow-bore capillary column ; Polycyclic aromatic compounds, PAC ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The combination of supercritical fluid extraction, high resolution capillary supercritical fluid chromatography, and Fourier transform infrared microspectrometry is described for the separation and identification of polycyclic aromatic hydrocarbons in a coal tar pitch. The variable solvating power of the supercritical fluid was utilized to selectively fractionate the sample. The fluid extract was decompressed through a frit restrictor into the sample cavity of a cooled microvalve injector, where the analytes were deposited and concentrated for subsequent chromatographic analysis. Several of the analytes separated in the chromatograph were collected on a potassium bromide disc at a solvent elimination inter-face for subsequent infrared analysis involving the use of an infra-red microscope accessory. The spectra obtained show the power of this detection technique for distinguishing between isomers.

Additional Material: 11 Ill.