Lateral diffusion of lipids in complex biological membranes.

O’Leary, Timothy J.

doi:10.1073/pnas.84.2.429

Cited by 35 publications

(28 citation statements)

References 22 publications

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“…The results obtained with DPH show a 9 to 21% increase in the anisotropy values (P Յ 0.001) in the opaque variants compared with the trans- It was shown in Escherichia coli that changes in cell surface physical properties, such as phase transition temperature and membrane microviscosity, show a positive linear correlation with the proportion of unsaturated fatty acids in the bacterial lipids (14). In this study, the lipid acyl chain profile of four opaque-transparent S. pneumoniae strains shows that the two variants carry the same types of fatty acyl residues, mainly saturated and unsaturated straight C 16 and C 18 acids, as reported before for other strains of S. pneumoniae (24). However, the ratio of unsaturated to saturated fatty acids was increased in the transparent variants compared with the opaque variants.…”

Section: Discussionmentioning

confidence: 54%

“…It is well known that polypeptides, proteins, and other nonlipid membrane constituents may significantly reduce the lateral diffusion of lipids in biological membranes (16). In addition, pyrene diffusion and excimer formation may be hampered by the inhomogeneity of the membrane.…”

Section: Discussionmentioning

confidence: 99%

“…In Table 6, the relative percentages of the cell fatty acids of two S. pneumoniae opaque-transparent pairs are reported. The two variants carry the same types of fatty acyl residues, mainly saturated and unsaturated straight C 16 and C 18 acids. However, the proportions of the various fatty acids varied.…”

Section: Membrane Dynamic Characteristics In Liposomesmentioning

confidence: 99%

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Differences in Membrane Fluidity and Fatty Acid Composition between Phenotypic Variants of Streptococcus pneumoniae

Aricha

Fishov

Cohen³

et al. 2004

J Bacteriol

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Phase variation in the colonial opacity of Streptococcus pneumoniae has been implicated as a factor in the pathogenesis of pneumococcal disease. This study examined the relationship between membrane characteristics and colony morphology in a few selected opaque-transparent couples of S. pneumoniae strains carrying different capsular types. Membrane fluidity was determined on the basis of intermolecular excimerization of pyrene and fluorescence polarization of 1,6-diphenyl 1,3,5-hexatriene (DPH). A significant decrease, 16 to 26% (P < 0.05), in the excimerization rate constant of the opaque variants compared with that of the transparent variants was observed, indicating higher microviscosity of the membrane of bacterial cells in the opaque variants. Liposomes prepared from phospholipids of the opaque phenotype showed an even greater decrease, 27 to 38% (P < 0.05), in the pyrene excimerization rate constant compared with that of liposomes prepared from phospholipids of bacteria with the transparent phenotype. These findings agree with the results obtained with DPH fluorescence anisotropy, which showed a 9 to 21% increase (P < 0.001) in the opaque variants compared with the transparent variants. Membrane fatty acid composition, determined by gas chromatography, revealed that the two variants carry the same types of fatty acids but in different proportions. The trend of modification points to the presence of a lower degree of unsaturated fatty acids in the opaque variants compared with their transparent counterparts. The data presented here show a distinct correlation between phase variation and membrane fluidity in S. pneumoniae. The changes in membrane fluidity most probably stem from the observed differences in fatty acid composition.Phase variation in the colonial opacity of Streptococcus pneumoniae has been implicated as a factor in the pathogenesis of pneumococcal disease (27). The different appearance of bacterial colonies is assumed to result from the spontaneous and reversible phase variation of surface components, the identity of which is not yet clear. The frequency of switching is highly variable from isolate to isolate, ranging from 10 Ϫ3 to 10 Ϫ6 per generation. The significance of opacity variation in the biology of pneumococcal infection in vivo was examined by using animal models of nasopharyngeal colonization and bacteremia. Transparent variants persist in the nasopharynx in vivo and show greater adherence to human lung epithelial cells. However, experiments performed with an adult mouse model of sepsis showed a strong selection for organisms with the opaque morphology during invasive infections (28).Genetic experiments were used to isolate a single locus able to confer altered colony opacity at a higher frequency than the background rate (18). The opacity locus was found to be associated with two genes in the presumed glycerol operon, glpF and glpD, required for glycerol metabolism in other bacteria. This finding raises the possibility that phase variation in S. pneumoniae is linked to the mechani...

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Section: Discussionmentioning

confidence: 54%

Section: Discussionmentioning

confidence: 99%

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Differences in Membrane Fluidity and Fatty Acid Composition between Phenotypic Variants of Streptococcus pneumoniae

Aricha

Fishov

Cohen³

et al. 2004

J Bacteriol

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“…These findings may be explained by the presence of the scaffold protein, which induces a decrease of lipid diffusion and motions inside the nanodisc belt. However, unlike liposomes, these steric restraints are likely to reflect a more realistic environment for lipids because proteins, rafts, glycolipids and sterols influence lipid diffusion in the cell 37. Furthermore, the restricted area in the nanodiscs appears to drastically reduce the cooperative effect of lipid assembly during the phase transition, which increases fluidity above the phase transition temperature.…”

Section: Resultsmentioning

confidence: 99%

Lipid Internal Dynamics Probed in Nanodiscs

et al. 2017

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Nanodiscs offer a very promising tool to incorporate membrane proteins into native‐like lipid bilayers and an alternative to liposomes to maintain protein functions and protein–lipid interactions in a soluble nanoscale object. The activity of the incorporated membrane protein appears to be correlated to its dynamics in the lipid bilayer and by protein–lipid interactions. These two parameters depend on the lipid internal dynamics surrounded by the lipid‐encircling discoidal scaffold protein that might differ from more unrestricted lipid bilayers observed in vesicles or cellular extracts. A solid‐state NMR spectroscopy investigation of lipid internal dynamics and thermotropism in nanodiscs is reported. The gel‐to‐fluid phase transition is almost abolished for nanodiscs, which maintain lipid fluid properties for a large temperature range. The addition of cholesterol allows fine‐tuning of the internal bilayer dynamics by increasing chain ordering. Increased site‐specific order parameters along the acyl chain reflect a higher internal ordering in nanodiscs compared with liposomes at room temperature; this is induced by the scaffold protein, which restricts lipid diffusion in the nanodisc area.

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“…Short-range techniques, such as quasielastic neutron scattering (QENS), have been thought to measure the rapid rattling-in-a-cage motion, whereas long-range techniques, such as fluorescence recovery after photobleaching, have been assumed to gauge the slower motion consisting of jumps between cages. Phenomenological free volume models based on the jump-diffusion model have been used to interpret the dependence of lateral diffusion coefficients on temperature and membrane composition (Galla et al 1979;MacCarthy and Kozak 1982;O'Leary 1987;Almeida et al 1992). However, no direct experimental evidence for the jumps as a dominating diffusion mechanism has been reported.…”

Section: Complex Concerted Dynamics In Membranesmentioning

confidence: 99%

Lipid Simulations: A Perspective on Lipids in Action

Vattulainen

Róg²

2011

Cold Spring Harbor Perspectives in Biology

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In this article, we provide an overview of lipid simulations, describing how a computer can be used as a laboratory for lipid research. We briefly discuss the methodology of lipid simulations followed by a number of topical applications that show the benefit of computer modeling for complementing experiments. In particular, we show examples of cases in which simulations have made predictions of novel phenomena that have later been confirmed by experimental studies. Overall, the applications discussed in this article focus on the most recent state of the art and aim to provide a perspective of where the field of lipid simulations stands at the moment.

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Lateral diffusion of lipids in complex biological membranes.

Cited by 35 publications

References 22 publications

Differences in Membrane Fluidity and Fatty Acid Composition between Phenotypic Variants of Streptococcus pneumoniae

Differences in Membrane Fluidity and Fatty Acid Composition between Phenotypic Variants of Streptococcus pneumoniae

Lipid Internal Dynamics Probed in Nanodiscs

Lipid Simulations: A Perspective on Lipids in Action

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