Membrane Remodeling of Giant Vesicles in Response to Localized Calcium Ion Gradients

In a wide variety of fundamental cell processes, such as membrane trafficking and apoptosis, cell membrane shape transitions occur concurrently with local ...

Chalmers University of Technology

Entanglements and trefoil knots on surfactant nanotubes in the liquid phase were produced by a combination of network self-organization and micromanipulation. The resulting knots are self-tightening, and the tightening is driven by minimization of surface free energy of the surfactant membrane material. The formation of the knot and the steady-state knot at quasi-equilibrium can be directly followed and localized by using fluorescence microscopy. Knots on nanotubes can be used as nanoscale mechanical tweezers for trapping and manipulation of single nano- and micrometer-sized high-aspect ratio objects. Furthermore, we demonstrate that by controlling the surface tension, objects captured by a knot can be transported along given trajectories defined by the nanotube axes.

Mechanical tweezer action by self-tightening knots in surfactant nanotubes.

Nous &eacute;tudions la formation de jonctions Y en nanotubes de surfactant brancher des v&eacute;sicules. Bas&eacute; sur des observations exp&eacute;rimentales de l&#39;&eacute;coulement de surfactant sur les nanotubes, nous concluons qu&#39;une jonction Y propage avec un m&eacute;canisme de transferts. Les tensio-actifs des deux branches de nanotube subissent de m&eacute;lange 1:1 &agrave; la jonction et forment spontan&eacute;ment la prolongation de la troisi&egrave;me branche du nanotube. Compte tenu de la tension, pilot&eacute; par le d&eacute;bit de l&#39;agent tensio-actif, nous d&eacute;veloppons un mod&egrave;le pour la dynamique de jonction Y qui est en accord quantitatif avec les donn&eacute;es exp&eacute;rimentales.

Dynamique de tirette de jonctions de nanotube Y agent tensio-actif.

Wir untersuchen die Bildung von Y Kreuzungen in Tensid-Nanotubes Bl&auml;schen verbinden. Basierend auf experimentellen Beobachtungen der Tensid Str&ouml;mung auf die Nanor&ouml;hren, schlie&szlig;en wir, dass eine Y-Kreuzung mit einem zipperlike Mechanismus ausbreitet. Die Tenside aus zwei Nanotube Verzweigungen unterzogen werden 1:1 mischen, an der Kreuzung und spontan bilden die Erweiterung der dritten Nanotube-Niederlassung. Unter Ber&uuml;cksichtigung die Spannung angetrieben Tensid-Fluss, entwickeln wir ein Modell f&uuml;r die Dynamik der Y-Kreuzung, die in quantitative &Uuml;bereinstimmung mit den experimentellen Daten ist.

Rei&szlig;verschluss Dynamik Tensid Nanotube Y Kreuzungen.

Indaghiamo la formazione delle giunzioni Y in nanotubi di tensioattivo collegando le vescicole. Basato su osservazioni sperimentali del flusso del tensioattivo su nanotubi, possiamo concludere che una giunzione a Y si propaga con un meccanismo di zipperlike. I tensioattivi da due rami di nanotubi sottoporsi all&#39;incrocio di miscelazione 1:1 e formano spontaneamente l&#39;estensione del terzo ramo di nanotubi. Prendendo in considerazione la tensione basato su flusso di tensioattivo, sviluppiamo un modello per le dinamiche di giunzione Y che sono in accordo quantitativo con i dati sperimentali.

Dinamiche di cerniera delle giunzioni nanotubo Y tensioattivo.

&#x6211;&#x4EEC;&#x8C03;&#x67E5; Y &#x8DEF;&#x53E3;&#x4E2D;&#x8868;&#x9762;&#x6D3B;&#x6027;&#x5242;&#x7EB3;&#x7C73;&#x7BA1;&#x8FDE;&#x63A5;&#x5C0F;&#x6CE1;&#x7684;&#x5F62;&#x6210;&#x3002;&#x57FA;&#x4E8E;&#x8868;&#x9762;&#x6D3B;&#x6027;&#x5242;&#x5BF9;&#x7EB3;&#x7C73;&#x7BA1;&#x6D41;&#x7684;&#x5B9E;&#x9A8C;&#x89C2;&#x6D4B;&#xFF0C;&#x6211;&#x4EEC;&#x5F97;&#x51FA;&#x7684;&#x7ED3;&#x8BBA; Y &#x4EA4;&#x754C;&#x5904;&#x4F20;&#x64AD;&#x4E0E; zipperlike &#x7684;&#x673A;&#x5236;&#x3002;&#x4ECE;&#x4E24;&#x4E2A;&#x7EB3;&#x7C73;&#x7BA1;&#x5206;&#x652F;&#x8868;&#x9762;&#x6D3B;&#x6027;&#x5242;&#x7ECF;&#x8FC7; 1&#xFF1A; 1 &#x7684;&#x4EA4;&#x754C;&#xFF0C;&#x6405;&#x62CC;&#x548C;&#x81EA;&#x53D1;&#x5F62;&#x6210;&#x7684;&#x7B2C;&#x4E09;&#x4E2A;&#x7684;&#x7EB3;&#x7C73;&#x7BA1;&#x5206;&#x652F;&#x6269;&#x5C55;&#x3002;&#x6211;&#x4EEC;&#x8003;&#x8651;&#x5230;&#x9A71;&#x52A8;&#x8868;&#x9762;&#x6D3B;&#x6027;&#x5242;&#x6D41;&#x7684;&#x7D27;&#x5F20;&#x5173;&#x7CFB;&#xFF0C;&#x53D1;&#x5C55;&#x5B9A;&#x91CF;&#x534F;&#x8BAE;&#x4E0B;&#x7684;&#x5B9E;&#x9A8C;&#x6570;&#x636E;&#x662F; Y &#x4EA4;&#x754C;&#x5904;&#x52A8;&#x529B;&#x5B66;&#x6A21;&#x578B;&#x3002;

&#x62C9;&#x94FE;&#x7684;&#x8868;&#x9762;&#x6D3B;&#x6027;&#x5242;&#x7EB3;&#x7C73;&#x7BA1; Y &#x8DEF;&#x53E3;&#x7684;&#x52A8;&#x6001;&#x3002;

We investigate the formation of Y junctions in surfactant nanotubes connecting vesicles. Based on experimental observations of the surfactant flow on the nanotubes, we conclude that a Y junction propagates with a zipperlike mechanism. The surfactants from two nanotube branches undergo 1:1 mixing at the junction, and spontaneously form the extension of the third nanotube branch. Taking into account the tension driven surfactant flow, we develop a model for the Y junction dynamics that is in quantitative agreement with the experimental data.

Zipper dynamics of surfactant nanotube Y junctions.

Y &#x63A5;&#x5408;&#x306B;&#x304A;&#x3051;&#x308B;&#x754C;&#x9762;&#x6D3B;&#x6027;&#x5264;&#x30CA;&#x30CE;&#x30C1;&#x30E5;&#x30FC;&#x30D6;&#x306E;&#x5C0F;&#x80DE;&#x306E;&#x63A5;&#x7D9A;&#x306E;&#x5F62;&#x6210;&#x3092;&#x8ABF;&#x67FB;&#x3057;&#x307E;&#x3059;&#x3002;&#x30CA;&#x30CE;&#x30C1;&#x30E5;&#x30FC;&#x30D6;&#x306E;&#x754C;&#x9762;&#x6D3B;&#x6027;&#x5264;&#x6D41;&#x308C;&#x306E;&#x5B9F;&#x9A13;&#x7684;&#x89B3;&#x6E2C;&#x306B;&#x57FA;&#x3065;&#x3044;&#x3066;&#x3001;Y &#x63A5;&#x5408; zipperlike &#x306E;&#x30E1;&#x30AB;&#x30CB;&#x30BA;&#x30E0;&#x3092;&#x4F1D;&#x642C;&#x3059;&#x308B;&#x3053;&#x3068;&#x3092;&#x7DE0;&#x7D50;&#x3057;&#x307E;&#x3059;&#x3002;&#x754C;&#x9762;&#x6D3B;&#x6027;&#x5264; 2 &#x3064;&#x30AB;&#x30FC;&#x30DC;&#x30F3;&#x30CA;&#x30CE; &#x30C1;&#x30E5;&#x30FC;&#x30D6;&#x306E;&#x5206;&#x5C90;&#x304B;&#x3089;&#x63A5;&#x5408;&#x90E8;&#x3067;&#x306F;, 1:1 &#x306E;&#x6DF7;&#x5408;&#x3092;&#x53D7;&#x3051;&#x308B;&#x3057;&#x3001;&#x30AB;&#x30FC;&#x30DC;&#x30F3;&#x30CA;&#x30CE; &#x30C1;&#x30E5;&#x30FC;&#x30D6;&#x306E; 3 &#x756A;&#x76EE;&#x306E;&#x5206;&#x5C90;&#x306E;&#x5EF6;&#x9577;&#x3092;&#x81EA;&#x767A;&#x7684;&#x306B;&#x5F62;&#x6210;&#x3057;&#x307E;&#x3059;&#x3002;&#x754C;&#x9762;&#x6D3B;&#x6027;&#x5264;&#x6D41;&#x308C;&#x306E;&#x5F35;&#x529B;&#x3092;&#x8003;&#x616E;&#x3059;&#x308B;&#x3068;, &#x5B9F;&#x9A13;&#x30C7;&#x30FC;&#x30BF;&#x3068;&#x5B9A;&#x91CF;&#x7684;&#x306A;&#x4E00;&#x81F4;&#x3067;&#x3059; Y &#x30B8;&#x30E3;&#x30F3;&#x30AF;&#x30B7;&#x30E7;&#x30F3;&#x306E;&#x52D5;&#x529B;&#x5B66;&#x30E2;&#x30C7;&#x30EB;&#x3092;&#x958B;&#x767A;&#x3057;&#x307E;&#x3059;&#x3002;

&#x754C;&#x9762;&#x6D3B;&#x6027;&#x5264;&#x30CA;&#x30CE;&#x30C1;&#x30E5;&#x30FC;&#x30D6; Y &#x63A5;&#x5408;&#x7CFB;&#x306E;&#x30B8;&#x30C3;&#x30D1;&#x30FC;&#x306E;&#x30C0;&#x30A4;&#x30CA;&#x30DF;&#x30AF;&#x30B9;&#x3002;

&#xC6B0;&#xB9AC; &#xC870;&#xC0AC; Y &#xC811;&#xD569; &#xC18C;&#xD3EC;&#xC5D0; &#xC5F0;&#xACB0; &#xD558;&#xB294; &#xACC4;&#xBA74; &#xD65C;&#xC131; &#xC81C; &#xB098;&#xB178;&#xD29C;&#xBE0C;&#xC758; &#xD615;&#xC131;. &#xB098;&#xB178;&#xD29C;&#xBE0C;&#xC5D0; &#xACC4;&#xBA74; &#xD65C;&#xC131; &#xC81C; &#xD750;&#xB984;&#xC758; &#xC2E4;&#xD5D8; &#xAD00;&#xCC30;&#xC744; &#xBC14;&#xD0D5;&#xC73C;&#xB85C;, &#xC6B0;&#xB9AC;&#xB294; Y &#xC815;&#xC158; zipperlike &#xBA54;&#xCEE4;&#xB2C8;&#xC998;&#xC73C;&#xB85C; &#xC804;&#xD30C; &#xACB0;&#xB860;. &#xB450; &#xB098;&#xB178;&#xD29C;&#xBE0C; &#xBD84;&#xAE30;&#xC5D0;&#xC11C; &#xACC4;&#xBA74; &#xC811;&#xD569;&#xC5D0; 1:1 &#xD63C;&#xD569; &#xBC1B; &#xB2E4; &#xACE0; &#xC800;&#xC808;&#xB85C; &#xC138; &#xBC88;&#xC9F8; &#xB098;&#xB178;&#xD29C;&#xBE0C; &#xC9C0;&#xC810; &#xD655;&#xC7A5;&#xC744; &#xD615;&#xC131; &#xD55C;&#xB2E4;. &#xACC4;&#xBA74; &#xD65C;&#xC131; &#xC81C; &#xD750;&#xB984;&#xC744; &#xC81C;&#xC5B4; &#xD558;&#xB294; &#xAE34;&#xC7A5;&#xC744; &#xACE0;&#xB824; &#xC6B0;&#xB9AC; &#xC2E4;&#xD5D8; &#xB370;&#xC774;&#xD130;&#xC640; &#xC591;&#xC801; &#xACC4;&#xC57D;&#xC5D0; &#xC788;&#xB294; Y &#xC811;&#xD569; &#xC5ED;&#xD559;&#xC5D0; &#xB300; &#xD55C; &#xBAA8;&#xB378;&#xC744; &#xAC1C;&#xBC1C;&#xD560; &#xC218; &#xC788;&#xC2B5;&#xB2C8;&#xB2E4;.

&#xACC4;&#xBA74; &#xD65C;&#xC131; &#xC81C; &#xB098;&#xB178;&#xD29C;&#xBE0C; Y &#xC811;&#xD569;&#xC758; &#xC9C0;&#xD37C; &#xC5ED;&#xD559;&#xC785;&#xB2C8;&#xB2E4;.

Investigamos la formaci&oacute;n Y cruces en nanotubos de surfactante conexi&oacute;n ves&iacute;culas. Basado en observaciones experimentales del flujo del surfactante en los nanotubos, concluimos que un cruce Y se propaga con un mecanismo de zipperlike. Los tensioactivos de dos ramas de nanotubos se someten a la mezcla 1:1 en el cruce y forman espont&aacute;neamente la extensi&oacute;n de la tercera rama de nanotubos. Teniendo en cuenta la tensi&oacute;n por flujo de surfactante, desarrollamos un modelo para la din&aacute;mica de cruce Y que es cuantitativa de acuerdo con los datos experimentales.

Din&aacute;mica de la cremallera de uniones de nanotubos Y surfactante.

Bilayer membranes envelope cells as well as organelles, and constitute the most ubiquitous biological material found in all branches of the phylogenetic tree. Cell membrane rupture is an important biological process, and substantial rupture rates are found in skeletal and cardiac muscle cells under a mechanical load. Rupture can also be induced by processes such as cell death, and active cell membrane repair mechanisms are essential to preserve cell integrity. Pore formation in cell membranes is also at the heart of many biomedical applications such as in drug, gene and short interfering RNA delivery. Membrane rupture dynamics has been studied in bilayer vesicles under tensile stress, which consistently produce circular pores. We observed very different rupture mechanics in bilayer membranes spreading on solid supports: in one instance fingering instabilities were seen resulting in floral-like pores and in another, the rupture proceeded in a series of rapid avalanches causing fractal membrane fragmentation. The intermittent character of rupture evolution and the broad distribution in avalanche sizes is consistent with crackling-noise dynamics. Such noisy dynamics appear in fracture of solid disordered materials, in dislocation avalanches in plastic deformations and domain wall magnetization avalanches. We also observed similar fractal rupture mechanics in spreading cell membranes.

Fractal avalanche ruptures in biological membranes.

Experimental and theoretical studies on ion-lipid interactions predict that binding of calcium ions to cell membranes leads to macroscopic mechanical effects and membrane remodeling. Herein, we provide experimental evidence that a point source of Ca acting upon a negatively charged membrane generates spontaneous curvature and triggers the formation of tubular protrusions that point away from the ion source. This behavior is rationalized by strong binding of the divalent cations to the surface of the charged bilayer, which effectively neutralizes the surface charge density of outer leaflet of the bilayer. The mismatch in the surface charge density of the two leaflets leads to nonzero spontaneous curvature. We probe this mismatch through the use of molecular dynamics simulations and validate that calcium ion binding to a lipid membrane is sufficient to generate inward spontaneous curvature, bending the membrane. Additionally, we demonstrate that the formed tubular protrusions can be translated along the vesicle surface in a controlled manner by repositioning the site of localized Ca exposure. The findings demonstrate lipid membrane remodeling in response to local chemical gradients and offer potential insights into the cell membrane behavior under conditions of varying calcium ion concentrations.

Membrane Tubulation in Lipid Vesicles Triggered by the Local Application of Calcium Ions.

Membrane tubular structures are important communication pathways between cells and cellular compartments. Studying these structures in their native environment is challenging, due to the complexity of membranes and varying chemical conditions within and outside of the cells. This work demonstrates that a calcium ion gradient, applied to a synthetic lipid nanotube, triggers lipid flow directed toward the application site, resulting in the formation of a bulge aggregate. This bulge can be translated in a contactless manner by moving a calcium ion source along the lipid nanotube. Furthermore, entrapment of polystyrene nanobeads within the bulge does not tamper the bulge movement and allows transporting of the nanoparticle cargo along the lipid nanotube. In addition to the synthetic lipid nanotubes, the response of cell plasma membrane tethers to local calcium ion stimulation is investigated. The directed membrane transport in these tethers is observed, but with slower kinetics in comparison to the synthetic lipid nanotubes. The findings of this work demonstrate a novel and contactless mode of transport in lipid nanotubes, guided by local exposure to calcium ions. The observed lipid nanotube behavior can advance the current understanding of the cell membrane tubular structures, which are constantly reshaped during dynamic cellular processes.

Tatsiana Lobovkina

Department Of Chemistry and Chemical Engineering

Chalmers University of Technology

Membrane Remodeling of Giant Vesicles in Response to Localized Calcium Ion Gradients

Tatsiana Lobovkina

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department Of Chemistry and Chemical Engineering

Chalmers University of Technology

Membrane Remodeling of Giant Vesicles in Response to Localized Calcium Ion Gradients

Department Of Chemistry and Chemical Engineering