Universal Behavior of Membranes with Sterols

Henriksen, Jonas Rosager; Rowat, Amy C.; Brief, Elana; Hsueh, Ya-Wei; Thewalt, Jenifer; Zuckermann, Martin J.; Ipsen, John Hjort

doi:10.1529/biophysj.105.067652

Cited by 252 publications

(220 citation statements)

References 65 publications

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“…4 A and are inversely proportional to the intercept of the fit with the vertical axis, as described in more detail in Materials and Methods. From this analysis we obtained a bending modulus estimate of the bare bilayer system of (1.5 5 0.13) Â 10 À20 J, close to the values previously reported for simulations of pure DPPC lipid bilayers (4 Â 10 À20 J) (50) and to experimental data for POPC bilayers ranging between 6.7 and 16 Â 10 À20 J (64)(65)(66)(67)(68). The values obtained in our simulations are slightly lower than previously reported, which might be due to the temperature: our simulations are performed at physiological temperature (310 K, 37 C) whereas previously reported experimental data were obtained at lower temperatures.…”

Section: Effects Of Povpc and Pgpc On The Bending Modulus Of The Bilasupporting

confidence: 85%

Molecular-Scale Biophysical Modulation of an Endothelial Membrane by Oxidized Phospholipids

Ayee

LeMaster

Shentu

et al. 2017

Biophysical Journal

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The influence of two bioactive oxidized phospholipids on model bilayer properties, membrane packing, and endothelial cell biomechanics was investigated computationally and experimentally. The truncated tail phospholipids, 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC) and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC), are two major oxidation products of the unsaturated phospholipid 1-palmitoyl-2-arachidonoyl-sn-glycero-phosphocholine. A combination of coarse-grained molecular dynamics simulations, Laurdan multiphoton imaging, and atomic force microscopy microindentation experiments was used to determine the impact of POVPC and PGPC on the structure of a multicomponent phospholipid bilayer and to assess the consequences of their incorporation on membrane packing and endothelial cell stiffness. Molecular simulations predicted differential bilayer perturbation effects of the two oxidized phospholipids based on the chemical identities of their truncated tails, including decreased bilayer packing, decreased bilayer bending modulus, and increased water penetration. Disruption of lipid order was consistent with Laurdan imaging results indicating that POVPC and PGPC decrease the lipid packing of both ordered and disordered membrane domains. Computational predictions of a larger membrane perturbation effect by PGPC correspond to greater stiffness of PGPC-treated endothelial cells observed by measuring cellular elastic moduli using atomic force microscopy. Our results suggest that disruptions in membrane structure by oxidized phospholipids play a role in the regulation of overall endothelial cell stiffness.

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Section: Effects Of Povpc and Pgpc On The Bending Modulus Of The Bilasupporting

confidence: 85%

Molecular-Scale Biophysical Modulation of an Endothelial Membrane by Oxidized Phospholipids

Ayee

LeMaster

Shentu

et al. 2017

Biophysical Journal

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“…We have only used the points for 1.00, 1.02 and 1.05 in order to calculate K a . We obtained K a ∼ 224.8 ± 7mN/m which is quite comparable to the experimental value 213±5 mN/m [42]. We show the fluctuation spectra for our simulations without an applied electric potential in Fig.…”

Section: A Without Applied Electrical Potentialsupporting

confidence: 86%

Tension moderation and fluctuation spectrum in simulated lipid membranes under an applied electric potential

Loubet

Lomholt

Khandelia

2013

The Journal of Chemical Physics

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We investigate the effect of an applied electric potential on the mechanics of a coarse grained POPC bilayer under tension. The size and duration of our simulations allow for a detailed and accurate study of the fluctuations. Effects on the fluctuation spectrum, tension, bending rigidity and bilayer thickness are investigated in detail. In particular the least square fitting technique is used to calculate the fluctuation spectra. The simulations confirm a recently proposed theory, that the effect of an applied electric potential on the membrane will be moderated by the elastic properties of the membrane. In agreement with the theory we find that the larger the initial tension the larger the effect of the electric potential. Application of the electric potential increases the amplitude of the long wavelength part of the spectrum and the bending rigidity is deduced from the short wavelength fluctuations. The effect of the applied electric potential on the bending rigidity is non-existent within error bars. However when the membrane is stretched there is a point where the bending rigidity is lowered due to a decrease of the thickness of the membrane. All these effects should prove important for mechanosensitive channels and biomembrane mechanics in general.

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“…1B). The energetic cost of the deformation, using standard material properties of 1-palmitoyl-2-oleoyl PC (POPC) bilayers (Table S1) (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27), is 60 kcal/mol, and the bending energy dominates over the compression and surface tension terms.…”

Section: Tmem16 Induces Large-scale Membrane Deformationsmentioning

confidence: 99%

Atomistic insight into lipid translocation by a TMEM16 scramblase

Bethel

Grabe

2016

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

100

159

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The transmembrane protein 16 (TMEM16) family of membrane proteins includes both lipid scramblases and ion channels involved in olfaction, nociception, and blood coagulation. The crystal structure of the fungal Nectria haematococca TMEM16 (nhTMEM16) scramblase suggested a putative mechanism of lipid transport, whereby polar and charged lipid headgroups move through the low-dielectric environment of the membrane by traversing a hydrophilic groove on the membrane-spanning surface of the protein. Here, we use computational methods to explore the membrane-protein interactions involved in lipid scrambling. Fast, continuum membrane-bending calculations reveal a global pattern of charged and hydrophobic surface residues that bends the membrane in a large-amplitude sinusoidal wave, resulting in bilayer thinning across the hydrophilic groove. Atomic simulations uncover two lipid headgroup-interaction sites flanking the groove. The cytoplasmic site nucleates headgroup-dipole stacking interactions that form a chain of lipid molecules that penetrate into the groove. In two instances, a cytoplasmic lipid interdigitates into this chain, crosses the bilayer, and enters the extracellular leaflet, and the reverse process happens twice as well. Continuum membrane-bending analysis carried out on homology models of mammalian homologs shows that these family members also bend the membrane-even those that lack scramblase activity. Sequence alignments show that the lipid-interaction sites are conserved in many family members but less so in those with reduced scrambling ability. Our analysis provides insight into how large-scale membrane bending and protein chemistry facilitate lipid permeation in the TMEM16 family, and we hypothesize that membrane interactions also affect ion permeation.TMEM16 | lipid scrambling | continuum membrane models | simulation | anoctamin T he compositional asymmetry between the leaflets of the plasma membrane influences the signaling properties of cells. Scramblases are a class of proteins that disrupt membrane asymmetry by facilitating the transfer of phospholipids from one leaflet to the other in an energy-independent manner. These transmembrane proteins play a role in events such as coagulation of the blood and cellular apoptosis by transporting phosphatidylserine (PS) from the inner leaflet to the outer leaflet of the plasma membrane (1). In particular, transmembrane protein 16 (TMEM16) family members have gained recent attention for their role in phospholipid scrambling in platelets and fungi. The TMEM16 family members have diverse functions. For example, TMEM16A and -B are calcium-activated chloride channels, TMEM16F is a nonspecific cation channel and scramblase, and the fungal Aspergillus fumigatus TMEM16 is another dual scramblase/ion channel (2-6).The structure of the Nectria haematococca TMEM16 (nhTMEM16) membrane protein revealed a possible mechanism for phospholipid conduction across the membrane (Fig. 1A) (7). The protein forms a dimer, and each subunit has a hydrophilic groove composed of polar...

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Universal Behavior of Membranes with Sterols

Cited by 252 publications

References 65 publications

Molecular-Scale Biophysical Modulation of an Endothelial Membrane by Oxidized Phospholipids

Molecular-Scale Biophysical Modulation of an Endothelial Membrane by Oxidized Phospholipids

Tension moderation and fluctuation spectrum in simulated lipid membranes under an applied electric potential

Atomistic insight into lipid translocation by a TMEM16 scramblase

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