scholarly journals On the one-sided action of amphotericin B on lipid bilayer membranes.

1996 ◽  
Vol 107 (1) ◽  
pp. 69-78 ◽  
Author(s):  
R A Brutyan ◽  
P McPhie
Keyword(s):  
Amphotericin B ◽  
Single Channel ◽  
Membrane Surface ◽  
Classical Model ◽  
Ionic Channels ◽  
Phospholipid Bilayer ◽  
Lipid Bilayer Membranes ◽  
Polyene Antibiotic ◽  
Bilayer Membranes ◽  
The One

The one-sided action of the polyene antibiotic, amphotericin B, on phospholipid bilayer membranes formed from synthetic phosphatidylcholines (DOPC and DPhPC) and sterols (ergosterol and cholesterol), has been investigated. We found formation of well-defined ionic channels for both sterols and not only for ergosterol-containing membranes (Bolard, J., P. Legrand, F. Heitz, and B. Cybulska. 1991. Biochemistry. 30:5707-5715). Characteristics of these channels were studied in the presence of different salts. It was found that the channels have comparable conductances but different lifetimes that are approximately 100-fold less in cholesterol-containing membranes than in ergosterol-containing ones. Channel blocking by tetraethylammonium (TEA) ions shows that TEA blockage of channels in the presence of cholesterol increases their lifetimes in analogy to the lengthening of lifetimes of protein channels blocked by local anesthetics (Neher, E., and J. H. Steinbach. 1978. J. Physiol. 277: 153-176). However, the effect of the blocker on single-channel conductance is very close for both sterols. The data support the classical model of amphotericin B pore formation from complexes initially lying on the membrane surface as nonconducting prepores. We explain the antibiotic's cytotoxic selectivity by differences in the lifetimes of the channels formed with different sterols and suggest that phosphatidylcholine-sterol membranes can be used as a tool for rapid estimation of polyene antibiotic cytotoxicity.

scholarly journals Alamethicin channels incorporated into frog node of ranvier: calcium-induced inactivation and membrane surface charges.

1982 ◽  
Vol 79 (3) ◽  
pp. 411-436 ◽  
Author(s):  
M D Cahalan ◽  
J Hall
Keyword(s):  
Lipid Bilayer ◽  
Surface Potential ◽  
Single Channel ◽  
Membrane Surface ◽  
Internal Surface ◽  
Peptide Antibiotic ◽  
Lipid Bilayer Membranes ◽  
Surface Charges ◽  
Myelinated Nerve ◽  
Bilayer Membranes

Alamethicin, a peptide antibiotic, partitions into artificial lipid bilayer membranes and into frog myelinated nerve membranes, inducing a voltage-dependent conductance. Discrete changes in conductance representing single-channel events with multiple open states can be detected in either frog node or lipid bilayer membranes. In 120 mM salt solution, the average conductance of a single channel is approximately 600 pS. The channel lifetimes are roughly two times longer in the node membrane than in a phosphatidylethanolamine bilayer at the same membrane potential. With 2 or 20 mM external Ca and internal CsCl, the alamethicin-induced conductance of frog nodal membrane inactivates. Inactivation is abolished by internal EGTA, suggesting that internal accumulation of calcium ions is responsible for the inactivation, through binding of Ca to negative internal surface charges. As a probe for both external and internal surface charges, alamethicin indicates a surface potential difference of approximately -20 to -30 mV, with the inner surface more negative. This surface charge asymmetry is opposite to the surface potential distribution near sodium channels.

Ionic channels induced by surfactin in planar lipid bilayer membranes

1991 ◽  
Vol 1064 (1) ◽  
pp. 13-23 ◽  
Author(s):  
J.D. Sheppard ◽  
C. Jumarie ◽  
D.G. Cooper ◽  
R. Laprade
Keyword(s):  
Lipid Bilayer ◽  
Ionic Channels ◽  
Planar Lipid Bilayer ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes

Real-Time Observation of Phospholipid Bilayer Membrane Restructuring Induced by Protein Molecules using Atomic Force Microscopy

2001 ◽  
Vol 7 (S2) ◽  
pp. 858-859
Author(s):  
Hong Xing You ◽  
Xiaoyang Qi ◽  
Lei Yu
Keyword(s):  
Atomic Force Microscopy ◽  
Real Time ◽  
Lipid Bilayer ◽  
Protein Interactions ◽  
Phospholipid Bilayer ◽  
Biological Processes ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Force Microscopy ◽  
Atomic Force

Atomic force microscopy (AFM) allows the surfaces of native biological materials to be imaged in aqueous solution with submolecular resolution. The ability to perform AFM imaging in aqueous and physiological environment has made it possible to monitor important biological processes in real time at high resolution. Currently, there is a great deal of interest in AFM studies of the structure and property of lipid bilayer membranes and protein interactions with lipid bilayer membranes. Lipid bilayer membranes in biological cells form a permeability barrier, which controls the flow of ions, water, and other molecules between biological cells and their environments, whereas membrane-bound and/or membrane-associated proteins are responsible for most of the dynamic functions carried out by the membrane. However, real-time AFM monitoring of dynamic biological processes has been challenged by the limited temporal resolution of AFM, potential physical damage to soft biological samples, and intrinsic complexity of biological processes. There are few successful examples of AFM real-time studies of dynamic biological events, particularly in the aspect of protein interactions with lipid bilayer membranes.We have attempted to use atomic force microscopy to study interactions between a particular protein, saposin C, and phospholipid bilayer membranes in real time. Saposin C (Sap C), a small glycoprotein, is an essential co-factor for the hydrolysis of glucosylceramide by glucosylceramidase in lysosomes, and a deficiency of Sap C leads to a variant form of Gauchers’ diseases. Supported planar phospholipid bilayer membranes were used in the study.

Pore-Forming Activity of Outer Membrane Extracts from the Unicellular Cyanobacterium Synechocystis sp. PCC 6714

1989 ◽  
Vol 44 (1-2) ◽  
pp. 165-169 ◽  
Author(s):  
Uwe J. Jürgens ◽  
Roland Benz
Keyword(s):  
Outer Membrane ◽  
Cell Walls ◽  
Pore Diameter ◽  
Single Channel ◽  
Outer Membrane Proteins ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Unicellular Cyanobacterium ◽  
Sds Page ◽  
Synechocystis Sp

Abstract Cell walls of the unicellular cyanobacterium Synechocystis sp. PCC 6714, isolated from cell homogenates, were found to be unusually resistant against extraction with various detergents, organic solvents, chaotropic agents, and proteases. The major outer membrane proteins (M r 67,000; 61,000; 94,000) were solubilized by differential SDS-extraction and purified by preparative SDS-PAGE. The extracted proteins, reconstituted into lipid bilayer membranes, formed two types of pores with single-channel conductances of 2.2 nS (pore diameter of 1.4 nm) and 0.3 nS (pore diameter not determined), respectively. Carotenoids and lipopolysaccharide were found to be associated with the extracted major proteins.

Interaction of Amphotericin B and Nystatin with Phospholipid Bilayer Membranes: Effect of Cholesterol

1975 ◽  
Vol 53 (6) ◽  
pp. 1072-1079 ◽  
Author(s):  
Michael A. Singer
Keyword(s):  
Membrane Fluidity ◽  
Amphotericin B ◽  
Local Anesthetics ◽  
Cholesterol Content ◽  
Phospholipid Bilayer ◽  
High Cholesterol ◽  
Na Transport ◽  
Bilayer Membranes ◽  
Multilamellar Liposomes ◽  
Transmembrane Channels

Sodium-22 efflux was measured in multilamellar liposomes, exposed to one of the two polyene antibiotics amphotericin B or nystatin. Polyene mediated 22Na transport progressively rises with membrane sterol concentrations up to about 20 mol %, but falls with higher cholesterol concentrations. The polyene induced 22Na movement in cholesterol rich liposomes could be 'restored' by the addition of either dibucaine or propranolol (two local anesthetics) to the aqueous solution. These observations are interpreted in terms of the model of De Kruijff and Demel (Biochim. Biophys. Acta, 339, 57–70, 1974). In this model, nystatin and amphotericin B first complex with cholesterol and then these complexes aggregate to form transmembrane channels. It is here proposed that the aggregation of these complexes is inhibited by a high cholesterol content (decreased membrane fluidity) but that the two local anesthetics, by disrupting phospholipid–sterol interactions (increased membrane fluidity), can 'restore' this process of aggregation.

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