Obtaining high-fidelity powder spectra in anisotropic media: Phase-cycled Hahn echo spectroscopy

Rance, Mark; Byrd, R. Andrew

doi:10.1016/0022-2364(83)90190-7

Cited by 264 publications

(262 citation statements)

References 9 publications

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“…The phase-cycled Hahn echo pulse sequence was used on samples that were supplemented with 10% deuterated water to provide an internal lock frequency control (33). Recycle time was 2 s, 90°pulse width was 30 s, delay between pulses was 100 s, sweep width was 38.46 kHz, acquisition time was 0.104 s, and transient number was 2000 -10,000.…”

Section: Methodsmentioning

confidence: 99%

Pore Formation by Equinatoxin II, a Eukaryotic Protein Toxin, Occurs by Induction of Nonlamellar Lipid Structures

Anderluh

Serra

Viero

et al. 2003

Journal of Biological Chemistry

125

109

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Pore formation in the target cell membranes is a common mechanism used by many toxins in order to kill cells. Among various described mechanisms, a toroidal pore concept was described recently in the course of action of small antimicrobial peptides. Here we provide evidence that such mechanism may be used also by larger toxins. Membrane-destabilizing effects of equinatoxin II, a sea anemone cytolysin, were studied by various biophysical techniques. 31 P NMR showed an occurrence of an isotropic component when toxin was added to multilamellar vesicles and heated. This component was not observed with melittin, ␣-staphylococcal toxin, or myoglobin. It does not originate from isolated small lipid structures, since the size of the vesicles after the experiment was similar to the control without toxin. Electron microscopy shows occurrence of a honeycomb structure, previously observed only for some particular lipid mixtures. The analysis of FTIR spectra of the equinatoxin II-lipid complex showed lipid disordering that is consistent with isotropic component observed in NMR. Finally, the cation selectivity of the toxin-induced pores increased in the presence of negatively charged phosphatidic acid, indicating the presence of lipids in the conductive channel. The results are compatible with the toroidal pore concept that might be a general mechanism of pore formation for various membrane-interacting proteins or peptides.Proteins and peptides with the capacity to increase membrane permeability have been elaborated by a large number of organisms and are used as toxins, effectors in immune response or apoptosis. One of the most commonly adopted mechanisms is the formation of pores in the targeted membrane as occurs, for example, with pore-forming toxins (PFT) 1 (1, 2).Bacterial PFT, protein molecules of M r Ͼ 30,000, usually follow two strategies; they either form a channel via insertion of a de novo generated transmembrane ␤ barrel (examples are staphylococcal ␣-toxin, the cholesterol-dependent cytolysins, and the protective antigen of anthrax toxin), or they insert a bundle of preexisting ␣-helices through the membrane (like colicins and crystal ␦-endotoxins) (3, 4). Smaller molecules, like antimicrobial peptides or peptide toxins with M r between 1000 and 5000, have developed a wider set of mechanisms (5). In fact, besides the ␤-barrel (e.g. protegrin) (6) and the ␣-helix bundle (e.g. alamethicin and other peptaibols) (7), some alternative strategies were found, which directly modify the bilayer organization of the membrane. They range from a generic destabilization (exemplified by the carpet-like model) (8) to the formation of specific mixed lipid-peptide structures, like the toroidal pore, which was observed with magainin (9) and melittin (10).Actinoporins are a peculiar class of eukaryotic PFT with intermediate M r , exclusively found in sea anemones. It is a family of cysteineless proteins with M r around 18,000 -20,000 and a preference for sphingomyelin (SM) (11). They form cation-selective pores with a diameter of ϳ2...

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Section: Methodsmentioning

confidence: 99%

Pore Formation by Equinatoxin II, a Eukaryotic Protein Toxin, Occurs by Induction of Nonlamellar Lipid Structures

Anderluh

Serra

Viero

et al. 2003

Journal of Biological Chemistry

125

109

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“…A phase cycled Hahn echo sequence (Rance and Byrd, 1983) with high power proton decoupling was used. The 90°pulse was 10 s, and the spectral width was 100 kHz.…”

Section: Methodsmentioning

confidence: 99%

Wild-type Escherichia coli Cells Regulate the Membrane Lipid Composition in a “Window” between Gel and Non-lamellar Structures

Morein

Andersson

Rilfors

et al. 1996

Journal of Biological Chemistry

350

287

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Escherichia coli strain K12 was grown at 17, 27, and 37°C. The acyl chain composition of the membrane lipids varied with the growth temperature; the fraction of cis-vaccenoyl chains decreased, and the fraction of palmitoyl chains increased, when the growth temperature was increased. However, the polar head group composition did not change significantly. The equilibria between lamellar and reversed non-lamellar phases of lipids extracted from the inner membrane (IM), and from both the membranes (IOM), were studied with NMR and x-ray diffraction. At temperatures above the growth temperature the lipid extracts formed a reversed hexagonal phase, or a bicontinuous cubic phase, depending on the degree of hydration of the lipids. It was observed that: 1) at equal elevations above the growth temperature, IM lipid extracts, as well as IOM lipid extracts, have a nearly equal ability to form nonlamellar phases; 2) IM extracts have a stronger tendency than IOM extracts to form non-lamellar phases; 3) nonlamellar phases are formed under conditions that are relatively close to the physiological ones; the membrane lipid monolayers are thus "frustrated"; and 4) as a consequence of the change of the acyl chain structures, the temperature for the lamellar gel to liquid crystalline phase transition is changed simultaneously, and in the same direction, as the temperature for the lamellar to non-lamellar phase transition. With a too large fraction of saturated acyl chains the membrane lipids enter a gel state, and with a too large fraction of unsaturated acyl chains the lipids transform to non-lamellar phases. It is thus concluded that the regulation of the acyl chain composition in wild-type cells of E. coli is necessary for the organism to be able to grow in a "window" between a lamellar gel phase and reversed non-lamellar phases.

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“…36 was used with gated broadband proton continuous wave decoupling at a field strength of 50 kHz. A π/2 pulse of 3 µs, an interpulse delay of 33 µs, a recycle delay of 5 s, an acquisition time of 20 ms and a dwell time of 5 µs were used, and 64 to 512 scans were acquired.…”

Section: Nuclear Magnetic Resonancementioning

confidence: 99%

Magnetically Oriented Bicelles with Monoalkylphosphocholines: Versatile Membrane Mimetics for Nuclear Magnetic Resonance Applications

et al. 2016

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Obtaining high-fidelity powder spectra in anisotropic media: Phase-cycled Hahn echo spectroscopy

Cited by 264 publications

References 9 publications

Pore Formation by Equinatoxin II, a Eukaryotic Protein Toxin, Occurs by Induction of Nonlamellar Lipid Structures

Pore Formation by Equinatoxin II, a Eukaryotic Protein Toxin, Occurs by Induction of Nonlamellar Lipid Structures

Wild-type Escherichia coli Cells Regulate the Membrane Lipid Composition in a “Window” between Gel and Non-lamellar Structures

Magnetically Oriented Bicelles with Monoalkylphosphocholines: Versatile Membrane Mimetics for Nuclear Magnetic Resonance Applications

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