The nature of lipidic particles and their roles polymorphic transitions

Hui, Sek Wen; Stewart, T.P.; Boni, Lawrence T.

doi:10.1016/0009-3084(83)90015-4

Cited by 72 publications

(80 citation statements)

References 22 publications

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“…Similar electron microscopic images in situations intermediate between bilayer and H n phase in PE/PC mixtures [60] and in cardiolipin containing systems [61] have been suggested to reflect closely packed inverted micelles; on the basis of X-ray diffraction studies however, others [56,62] have argued that these pseudo-crystalline structures in fact represent interwoven networks of branched rods which may be of either type I or II with the polar phase facing outside or inside, respectively, a view supported also by recent evidence [63]. A type II structure obviously is more likely in the melittin-cardiolipin complex in view of its relationship with the inverted HI~ phase which is favoured at high temperatures.…”

Section: Discussionmentioning

confidence: 65%

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Melittin induces HII phase formation in cardiolipin model membranes

Batenburg

Hibbeln

Verkleij

et al. 1987

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The interaction of melittin with bovine heart cardiolipin model membranes was investigated via binding assays, 3t P-NMR, freeze-fracture electron microscopy, small angle X-ray diffraction and fluorescence based fusion assays. A strong binding (K d < 10-7 M) appeared to be accompanied by the formation of large structures, resulting from a fusion process of extremely fast initial rate. As the melittin content is increased, bilayer structure is gradually lost and from a cardiolipin to melittin ratio of about 6 the lipid starts to organize itself in an hexagonal H ii phase. At lower temperatures (T < 40 ° C) the coexistence of another structure is observed, characterized by a broad isotropic 31p-NMR signal and giving rise to sharp X-ray reflections, most probably a cubic phase, as suggested also by freeze-fracture images, showing orderly stacked particles. The results are discussed in relation to contrasting observations on the structural changes induced by melittin in the zwitterionic phospholipid system of dipalmitoylphosphatidylcholine (Dufourcq, J. et al. (1986) Biochim. Biophys. Acta 859, 33-48). The biological relevance of the observations with respect to the process of protein insertion into membranes is indicated.

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Section: Discussionmentioning

confidence: 65%

“…4c of Ref. 60, that were interpreted to reflect inverted tubular structures. In the same reference the ill-defined pits observed at this melittin-lipid ratio (Fig.…”

Section: Freeze-fracture Electron Microscopymentioning

confidence: 96%

Melittin induces HII phase formation in cardiolipin model membranes

Batenburg

Hibbeln

Verkleij

et al. 1987

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…It should be stressed that very few detectable nonbilayer features appear at these compositions and temperatures. Only a small isotropic 31P NMR peak and sporadic lipidic particles were observed at these ranges (2,24,25). The fact that the data in Fig.…”

Section: Discussionmentioning

confidence: 77%

“…In fact, a large portion of the membrane lipids do not form bilayers at physiological conditions (pH, calcium concentration, and temperature). These so-called "nonbilayer" lipids generally prefer high curvature structures such as inverted hexagonal (HI,), inverted cubic, and "lipid particles" when dispersed in water (1,2). However, no such structures have ever been found in functioning biomembranes.…”

mentioning

confidence: 99%

Effects of lipid packing on polymorphic phase behavior and membrane properties.

Hui

Sen

1989

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

100

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The self assembly of phospholipid molecules in the bilayer form was considered in terms of equivalent molecular shapes representing intermolecular forces. The equivalent size of each phospholipid headgroup was approximated by the net atomic volume plus the volume of the associated water molecules, which was derived from water/ hydrocarbon partitioning experiments. The equivalent lengths ofunsaturated acyl chains were derived from the retention time data from chromatographic measurements. The spontaneous curvature of various phospholipid monolayers was calculated from their equivalent molecular shapes, and the energy required to flatten them to the bilayer plane was calculated, using the known bending modulus. With increasing bending energy, the mixtures showed increasing susceptibility to phospholipase A2, facilitated lipid tansfer rate by phospholipid exchange proteins, permeability to carboxyfluorescein, incorporation of human erythrocyte proteins, and calcium transport by CaATPase from sarcoplasmic reticulum in reconstituted vesicles. When the calculation was applied to known lipid compositions of nine cellular membranes, the protein/lipid ratio and phospholipid/cholesterol ratio were found to have a positive and a negative correlation, respectively, with the latent bending energy of the phospholipids. The energy expense in conforming to a bilayer phase may be an important physical parameter regarding the activity and the biogenesis of membranes.The regulated diversity in lipid composition of biological membranes is well recognized, but the need for such diversity is not fully understood. Apparently, the lipids in biological membranes do more than provide a passive barrier and a supporting matrix for membrane proteins. There is ample evidence that changes in lipid structure can influence the activity ofmembranes (1). The quest for maintaining a certain "fluidity" fails to explain the diversity of membrane lipid species. It is known that not all lipids found in biological membranes form bilayers when dispersed in water. In fact, a large portion of the membrane lipids do not form bilayers at physiological conditions (pH, calcium concentration, and temperature). These so-called "nonbilayer" lipids generally prefer high curvature structures such as inverted hexagonal (HI,), inverted cubic, and "lipid particles" when dispersed in water (1, 2). However, no such structures have ever been found in functioning biomembranes. It would thus seem that the ability of these lipid mixtures to form high curvature structures upon self assembly, rather than the inverted structures themselves, is needed for the proper functioning of biological membranes.The polymorphism or phase preference of any lipid is governed by the coherence force, which is the combined result of the exclusion volume, polarity, headgroup interactions, and van der Waals interactions between hydrocarbon chains, among others (3, 4). These forces are difficult to account for analytically; therefore the quantitative assessment of the energetics of bilay...

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“…Once bilayers are in direct contact, an interruption in bilayer continuity is needed to allow for the mixing of membrane components preceding fusion (Prestegard & Kantor, 1978). Thus, a form of bilayer discontinuity or transient destabilization of the bilayer is necessary for fusion to occur (Ahkong et al, 1975;Papahadjopoulos et al, 1977;Hui et al, 1981a;Hui et al, 1983b). Pure lipid systems are ideal for observing any associated nonbilayer configurations in connection with the fusogenic effect of PEG.…”

Section: Introductionmentioning

confidence: 98%

Alterations in phospholipid polymorphism by polyethylene glycol

1984

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The fusogen polyethylene glycol is shown to alter the polymorphism of dimyristoyl phosphatidylcholine, soybean phosphatidylethanolamine, bovine phosphatidylserine, egg phosphatidylcholine/cholesterol mixture, dilinoleoylphosphatidylethanolamine/palmitoyl-oleoylphosphatidy lcholine mixture, and egg lysolecithin. Suspension of these lipids in 50% polyethylene glycol (mol wt = 6000) reduces both the lamellar and the hexagonal II repeat spacings as measured by X-ray diffraction. An increase in the gel to liquid crystalline and bilayer to hexagonal transition temperatures are observed by freeze-fracture, X-ray diffraction, differential scanning calorimetry and 31P NMR. Freeze-fracture electron micrographs revealed different bilayer defects depending on the physical states of the lipid. Lipidic particles in mixtures containing unsaturated phosphatidylethanolamine is eliminated. Some of the influences of polyethylene glycol on lipids may be explained by its dehydrating effect. However, other nonfusogenic dehydrating agents failed to produce similar results. These findings are consistent with the proposal that close bilayer contact and the formation of bilayer defects are associated with the fusogenic properties of polyethylene glycol.

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The nature of lipidic particles and their roles polymorphic transitions

Cited by 72 publications

References 22 publications

Melittin induces HII phase formation in cardiolipin model membranes

Melittin induces HII phase formation in cardiolipin model membranes

Effects of lipid packing on polymorphic phase behavior and membrane properties.

Alterations in phospholipid polymorphism by polyethylene glycol

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