ZIB

Hits per page

hits 1 - 2 | 2 hits

Sorting

Electronic Resource

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

add to mindlist on the mindlist

Details

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

Permalink

Library	Location	Call Number	Volume/Issue/Year	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

Electronic Resource

Single-crystal electron-spin resonance study of the 4-phenyl-1,2,3,5-dithiadiazolyl radicalNRCC No. 30635. (1989)

Lee, F. L. ; Preston, K. F. ; Williams, A. J. ; [et al.]

Chichester : Wiley-Blackwell

Organic Magnetic Resonance 27 (1989), S. 1161-1165

add to mindlist on the mindlist

Details

ISSN: 0749-1581

Keywords: Electron spin resonance ; Electron paramagnetic resonance ; Free radical ; π-Radical ; Heterocyclic free radical ; g Tensor ; Hyperfine interaction tensor ; Nitrogen hyperfine interaction ; Dithiadiazolyl ; Dithiadiazolylium ; Dithiadiazolium ; Unpaired electron ; Unpaired electron spin density ; Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Single crystals of 4-phenyl-1,2,3,5-dithiadiazolium trithiatriazinide , prepared by the reduction of S5N5+AlCl4- in SO2 with , contain a trace paramagnetic impurity which is shown by EPR spectroscopy to be the dithiadiazolyl free radical . The g and 14N hyperfine tensors of the radical were deduced from measurements made throughout three mutually orthogonal planes of crystallographically aligned specimens: g = (2.0011, 2.0075, 2.0197); 14N(2) = (37.1, 11.3, 3.4 MHz.). Within experimental error, the two nitrogen hyperfine interaction tensors are collinear and have their maximum principal value aligned parallel to gmin and perpendicular to the plane of the host cation. The results are interpreted in terms of a planar π-radical which substitutes for the planar host cation, and which has considerable unpaired spin density in N(2px) atomic orbitals directed perpendicular to the heterocyclic ring.

Additional Material: 3 Ill.