Local Unbinding of Pinched Membranes
| Autor: | Samuel A. Safran, Roy Bar-Ziv, R. Menes, Elisha Moses |
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| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Physical Review Letters. 75:3356-3359 |
| ISSN: | 1079-7114 0031-9007 |
| DOI: | 10.1103/physrevlett.75.3356 |
| Popis: | Loosely bound membranes exhibit an unusual elastic response when pinched together by optical tweezers, locally unbinding to a large intermembrane distance. Tweezing a stack of many bound membranes produces extreme local swelling in the vicinity of the tweezing point. We introduce a model that incorporates bending elasticity, fluctuations, and intermembrane interactions to calculate the membrane profiles subject to a local pinch. Theoretically, we find strongly overshooting profiles in agreement with experiment. We predict scaling behavior of the overshoot with the pinch strength and size. PACS numbers: 82.65.Dp, 68. 10.Et, 87.22.Bt Adhesion of biological membranes involves both the attraction of two homogeneous surfaces [1] and the interactions of specific molecular binding sites [2,3]. Experiments suggest that binding sites are dominant locally. However, the overall binding of two membranes with localized "chemical stickers ' is strongly influenced by the elastic response and fluctuations of the embedding bilayer [4]. To study the overall membrane response to a single binding site, we study a simplified model system by locally pinching together two membranes with optical tweezers [5,6]. This system can also model "local collisions, " which are important in the study of interacting, flexible membranes and the understanding of their unbinding transition [7,8]. Previously, we showed that laser tweezers remove area from the membrane, inducing tension in membranes with limited area and thus driving shape transitions. In the present work the tweezers are used primarily as a mechanical tool, clamping at a point two large planar membranes, which effectively have unlimited area and allow only a negligible buildup of tension. We studied bilayers composed of dimyristoyl-phosphatidylcholine (DMPC) (Sigma) produced by a standard technique [9]. Our experimental setup is described elsewhere [10,11]. Typical working conditions were 30 C and laser intensities from 30 up to 150 mW. We selected sets of two or more nearly Oat membranes, which were sections either of huge vesicles or of lamellar sheets that extended from the bottom of the cell to its top. We chose sections of membranes that appeared to be bound or loosely bound, at a distance of -1 p, m. The membranes are pinched by the laser tweezers in the — 0.5 p, m region of the trap. Regardless of the |
| Databáze: | OpenAIRE |
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