Evidence for the “Cold Fusion” of Bilayer Membranes

Ravoo, Bart Jan; Kevelam, Jan; Weringa, W. D.; Engberts, Jan B. F. N.

doi:10.1021/jp9829748

Cited by 11 publications

(23 citation statements)

References 29 publications

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“…In the past few decades, the aggregation of vesicles has attracted special attention not only for its close relations to these biological processes as the analogous model, 3,4 but also for its practical importance in pharmacy and so on. [5][6][7] Normally, vesicle aggregation is induced by external additives. Salt-induced and polymerinduced vesicle aggregations have been well-investigated in numerous papers.…”

Section: Introductionmentioning

confidence: 99%

Temperature-Controlled Vesicle Aggregation in the Mixed System of Sodium n-Dodecyl Sulfate/n-Dodecyltributylammonium Bromide

et al. 2005

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Temperature-controlled vesicle aggregation was investigated in a catanionic surfactant system of sodium n-dodecyl sulfate/n-dodecyltributylammonium bromide. Vesicle aggregation took place as the temperature reached the critical value (Tc). Tc can be adjusted by the variations of the total surfactant concentration and the mixed molar ratio. It was also found that the temperature variation above Tc can greatly influence the vesicle aggregation rate. The vesicle aggregation process was irreversible as long as T >/= Tc, whereas the vesicle disaggregation process occurred only below Tc.

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Section: Introductionmentioning

confidence: 99%

Temperature-Controlled Vesicle Aggregation in the Mixed System of Sodium n-Dodecyl Sulfate/n-Dodecyltributylammonium Bromide

et al. 2005

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“…The amphiphilic compounds DDPBNS and DHPBNS are members of a family of synthetic lipids that provides a useful membrane mimetic system (Ravoo et al, 1996(Ravoo et al, , 1998(Ravoo et al, , 1999(Ravoo et al, , 2000. The molecular structures of DDPBNS and DHPBNS are presented in Fig.…”

Section: Introductionmentioning

confidence: 99%

Electron microscopic investigation of the morphology and calcium-induced fusion of lipid vesicles with an oligomerised inner leaflet

Ravoo

Stuart

Brisson

et al. 2001

Chemistry and Physics of Lipids

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The lipid head groups in the inner leaflet of unilamellar bilayer vesicles of the synthetic lipids DHPBNS and DDPBNS can be selectively oligomerised. Earlier studies have established that these vesicles fuse much slower and less extensively upon oligomerisation of the lipid head groups. The morphology and calcium-induced fusion of vesicles of DHPBNS and DDPBNS were investigated using cryo-electron microscopy. DHPBNS vesicles are not spherical but flattened, ellipsoidal structures. Upon addition of CaCl(2), DHPBNS vesicles with an oligomerised inner leaflet were occasionally observed in an arrested hemifused state. However, the evidence for hemifusion is not equivocal due to potential artefacts of sample preparation. DDPBNS vesicles show the expected spherical morphology. Upon addition of excess CaCl(2), DDPBNS vesicles fuse into dense aggregates that show a regular spacing corresponding to the bilayer width. Upon addition of EDTA, the aggregates readily disperse into large unilamellar vesicles. At low concentration of calcium ion, DDPBNS vesicles with an oligomerised inner leaflet form small multilamellar aggregates, in which a spacing corresponding to the bilayer width appears. Addition of excess EDTA results in slow dispersal of the Ca2+-lipid aggregates into a heterogeneous mixture of bilamellar, spherical vesicles and networks of thread-like vesicles. These lipid bilayer rearrangements are discussed within the context of shape transformations and fusion of lipid membranes.

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“…Previously, we observed a very small positive enthalpy for calcium-induced lipid bilayer merging (0.15-0.25 kJ/mol lipid for the C12 analogue of DHPBNS (Ravoo et al, 1998). Fusion of Sendai virus with DHPBNS vesicles is endothermic by about 1.5 kJ/mol viral lipid.…”

Section: Discussionmentioning

confidence: 83%

“…We have recently reported that calcium-induced fusion of small vesicles is endothermic by 0.15 ± 0.10 kJ/mol lipid and driven by a gain in entropy of both lipid and water molecules as a result of bilayer merging (Ravoo et al, 1998). On the other hand, fusion of influenza virus and liposomes is endothermic by 2.5-2.9 kJ/mol viral lipid (Nebel et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…After oligomerization of the lipid head groups, the vesicles aggregate upon addition of calcium ion, but calcium-induced fusion is strongly inhibited due to a combination of reduced lipid lateral diffusion and bilayer curvature effects (Ravoo et al, 1998(Ravoo et al, , 1999. We have exploited this membrane model system in a micro calorimetric study to determine the enthalpies associated with binding of calcium ion, vesicle aggregation, and bilayer fusion in the course of calcium-induced vesicle fusion, and we showed that fusion of small vesicles is associated with a small positive enthalpy (Ravoo et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Fusion of Sendai Virus With Vesicles of Oligomerizable Lipids: A Microcalorimetric Analysis of Membrane Fusion

Ravoo¹

2000

Cell Biology International

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Sendai virus fuses efficiently with small and large unilamellar vesicles of the lipid 1,2-di-nhexadecyloxypropyl-4-(beta-nitrostyryl) phosphate (DHPBNS) at pH 7.4 and 37°C, as shown by lipid mixing assays and electron microscopy. However, fusion is strongly inhibited by oligomerization of the head groups of DHPBNS in the bilayer vesicles. The enthalpy associated with fusion of Sendai virus with DHPBNS vesicles was measured by isothermal titration microcalorimetry, comparing titrations of Sendai virus into (i) solutions of DHPBNS vesicles (which fuse with the virus) and (ii) oligomerized DHPBNS vesicles (which do not fuse with the virus), respectively. The observed heat effect of fusion of Sendai virus with DHPBNS vesicles is strongly dependent on the buffer medium, reflecting a partial charge neutralization of the Sendai F and HN proteins upon insertion into the negatively-charged vesicle membrane. No buffer effect was observed for the titration of Sendai virus into oligomerized DHPBNS vesicles, indicating that inhibition of fusion is a result of inhibition of insertion of the fusion protein into the target membrane. Fusion of Sendai virus with DHPBNS vesicles is endothermic and entropy-driven. The positive enthalpy term is dominated by heat effects resulting from merging of the protein-rich viral envelope with the lipid vesicle bilayers rather than by the fusion of the viral with the vesicle bilayers per se.

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Evidence for the “Cold Fusion” of Bilayer Membranes

Cited by 11 publications

References 29 publications

Temperature-Controlled Vesicle Aggregation in the Mixed System of Sodium n-Dodecyl Sulfate/n-Dodecyltributylammonium Bromide

Temperature-Controlled Vesicle Aggregation in the Mixed System of Sodium n-Dodecyl Sulfate/n-Dodecyltributylammonium Bromide

Electron microscopic investigation of the morphology and calcium-induced fusion of lipid vesicles with an oligomerised inner leaflet

Fusion of Sendai Virus With Vesicles of Oligomerizable Lipids: A Microcalorimetric Analysis of Membrane Fusion

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