Nuclear magnetic resonance studies of the interaction of alamethicin with lecithin bilayers

Lau, Arthur L. Y.; Chan, Sunney I.

doi:10.1021/bi00721a010

Cited by 81 publications

(33 citation statements)

References 27 publications

(33 reference statements)

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“…This suspension was vortex-mixed for 1 min and then sonicated in a Branson bath sonicator at room temperature under nitrogen until the solution became clear. These procedures yielded essentially unilamellar vesicles (300 A diameter) as judged by negative staining electron microscopy [8]. Samples of this preparation (0.5 ml) were then centrifuged through 3 ml Sephadex G-50 (medium) (Pharmacia, Uppsala) gel-filtration columns twice in succession according to Neal and Florini [9].…”

Section: Preparation Of Unilamellar Vesiclesmentioning

confidence: 99%

Potential‐sensitive membrane association of a fluorescent dye

1987

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Unilamellar phosphatidylcholine/cholesterol (5:1, w/w) vesicles and the fluorescent dye safranine O mixed in appropriate ratios produced a membrane potential-dependent enhancement of dye fluorescence. The fluorescence enhancement was shown to be dependent on the sign and magnitude of valinomycin-induced potassium diffusion potentials. The enhancement and a blue-shifted maximum (both of which also occur in ethanol vs aqueous solution) provided evidence that the enhanced fluorescence arises from an additional population of safranine O molecules which become associated with a hydrophobic region of the vesicular membrane. Consistent with this interpretation, the polarization of safranine O fluorescence was also found to increase in a potential-dependent manner. A time-dependent decay of the fluorescence enhancementpresumably due to decay of the membrane potential -was attributed to non-specific ion leakage at valinomycin concentrations above 3/zM.

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Section: Preparation Of Unilamellar Vesiclesmentioning

confidence: 99%

Potential‐sensitive membrane association of a fluorescent dye

1987

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“…Several other studies have reported fusion of liposomes with other liposomes (11)(12)(13)(14)(15), thin lipid films (14-15), cells (3)(4)(5)(6)(7), and organelles (10). Persuasive evidence has also been offered that the lipids of uni-and multilamellar liposomes exchange with each other (11).…”

Section: Methodsmentioning

confidence: 97%

“…Persuasive evidence has also been offered that the lipids of uni-and multilamellar liposomes exchange with each other (11). Indeed, various chromatographic (11,13), ultrastructural (11,13), proton magnetic resonance spectroscopic (12,13), and optical (16) techniques have been used to demonstrate the formation of "fused" particles -larger than the parent populations. However, in contrast to compelling evidence that enzymes or macromolecules trapped within liposomes can be introduced by nonphagocytic means into target cells (4-7), transfer of solutes from one population of liposomes to another has not been demonstrated.…”

Section: Methodsmentioning

confidence: 99%

“…In order for protein-free, lipid vesicles to undergo fusion in vitro, somewhat unphysiological conditions must be established (11,12,15). Moreover, the periods of interaction required would appear to be too prolonged to account in satisfactory fashion for the fusion of natural membranes.…”

Section: Methodsmentioning

confidence: 99%

“…Although quantification of the process is difficult, varying degrees of success have been reported with such fusion systems as cell-cell (2, 3), cell-liposome (4)(5)(6)(7), organelle-organelle (8,9), organelle-liposome (10), and liposome-liposome (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Techniques used to demonstrate fusion have included light and electron microscopic observation (2-5, 9, 12, 14, 15), determination of the redistribution of labeled lipids and solutes between fusing species (3)(4)(5)(6)(7), and indirect measurements of optical properties of fusing vesicles (16).…”

mentioning

confidence: 99%

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Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes.

Dunham¹,

Babiarz²,

Israel³

et al. 1977

Proc. Natl. Acad. Sci. U.S.A.

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Fusion between vesicles, cells, or organelles may be defined as confluence of two membrane-bound compartments without access of their solutes to external milieu. To study fusion by this criterion, we have trapped the metallochromic calcium-sensitive dye, arsenazo III (AIII), partially calcium-saturated (AIIICa) Fusion of biological membranes is required for such processes as phagocytosis, secretion, cell division, and poly-or heterokaryon formation (1). Although quantification of the process is difficult, varying degrees of success have been reported with such fusion systems as cell-cell (2, 3), cell-liposome (4-7), organelle-organelle (8, 9), organelle-liposome (10), and liposome-liposome ( 1-13). Techniques used to demonstrate fusion have included light and electron microscopic observation (2-5, 9, 12, 14, 15), determination of the redistribution of labeled lipids and solutes between fusing species (3-7), and indirect measurements of optical properties of fusing vesicles (16

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Designing Foldamer–Foldamer Interactions in Solution: The Roles of Helix Length and Terminus Functionality in Promoting the Self‐Association of Aminoisobutyric Acid Oligomers

Pike¹,

Diemer²,

Raftery³

et al. 2014

Chemistry A European J

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The biological activity of antibiotic peptaibols has been linked to their ability to aggregate, but the structure-activity relationship for aggregation is not well understood. Herein, we report a systematic study of a class of synthetic helical oligomer (foldamer) composed of aminoisobutyric acid (Aib) residues, which mimic the folding behavior of peptaibols. NMR spectroscopic analysis was used to quantify the dimerization constants in solution, which showed hydrogen-bond donors at the N terminus promoted aggregation more effectively than similar modifications at the C terminus. Elongation of the peptide chain also favored aggregation. The geometry of aggregation in solution was investigated by means of titrations with [D6]DMSO and 2D NOE NMR spectroscopy, which allowed the NH protons most involved in intermolecular hydrogen bonds in solution to be identified. X-ray crystallography studies of two oligomers allowed a comparison of the inter- and intramolecular hydrogen-bonding interactions in the solid state and in solution and gave further insight into the geometry of foldamer-foldamer interactions. These solution-based and solid-state studies indicated that the preferred geometry for aggregation is through head-to-tail interactions between the N and C termini of adjacent Aib oligomers.

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Nuclear magnetic resonance studies of the interaction of alamethicin with lecithin bilayers

Abstract: The interaction of alamethicin with both unsonicated lecithin multilayers and sonicated bilayer vesicles has been investigated by nuclear magnetic resonance (nmr) spectroscopy and electron microscopy. It is shown that alamethicin is a surface active agent, which interacts primarily

Cited by 81 publications

References 27 publications

Potential‐sensitive membrane association of a fluorescent dye

Potential‐sensitive membrane association of a fluorescent dye

Membrane fusion: studies with a calcium-sensitive dye, arsenazo III, in liposomes.

Designing Foldamer–Foldamer Interactions in Solution: The Roles of Helix Length and Terminus Functionality in Promoting the Self‐Association of Aminoisobutyric Acid Oligomers

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