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DissertationDOI

Interplay Between Long-Range And Short-Range Interactions In Polymer Self-Assembly And Cell Adhesion

01 Jan 2008-
TL;DR: In this paper, reversible gelation of associating polymers and ligand-receptor interactions in membrane adhesion was studied, and the energy barrier of the adhesion as a result of membrane bending deformations and the double-well adhesion potential was calculated.
Abstract: Interplay between long-range and short-range interactions is a common theme in soft and biological matter, which results in complicated self-assembly behaviors. We study two examples of this interplay: reversible gelation of associating polymers and ligand-receptor interactions in membrane adhesion. In associating polymer solutions, the competition between the conformation flexibility of polymer chains and the enthalpic monomer interactions results in phase-separated micro-structures at the mesoscopic scale; both gelation and the microphase order-disorder transition are manifestations of this self-assembly. We further establish that reversible gelation is similar to the glass transition: both are characterized by ergodicity breaking, aperiodic micro-structures, and non-equilibrium relaxations over a finite temperature range. In the study of ligand-receptor interactions between surfaces, we emphasize the interplay between specific ligand-receptor binding, and generic physical interactions. We find that both the finite spatial extension of receptors and their mobilities affect their binding affinity. As a special case of the interplay between receptor binding and generic interactions, we study the dynamics of membrane adhesion that is mediated by receptor binding but fulfilled through membrane deformations. We calculate the energy barrier of the adhesion as a result of membrane bending deformations and the double-well adhesion potential, and analyze the different scenarios according to the shape of the adhesion potential by scaling arguments.

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Citations
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01 Mar 1996
TL;DR: In this paper, a mean-field phase diagram for conformationally symmetric diblock melts using the standard Gaussian polymer model is presented, which traverses the weak- to strong-segregation regimes, is free of traditional approximations.
Abstract: A mean-field phase diagram for conformationally symmetric diblock melts using the standard Gaussian polymer model is presented. Our calculation, which traverses the weak- to strong-segregation regimes, is free of traditional approximations. Regions of stability are determined for disordered (DIS) melts and for ordered structures including lamellae (L), hexagonally packed cylinders (H), body-centered cubic spheres (QIm3m), close-packed spheres (CPS), and the bicontinuous cubic network with Ia3d symmetry (QIa3d). The CPS phase exists in narrow regions along the order−disorder transition for χN ≥ 17.67. Results suggest that the QIa3d phase is not stable above χN ∼ 60. Along the L/QIa3d phase boundaries, a hexagonally perforated lamellar (HPL) phase is found to be nearly stable. Our results for the bicontinuous Pn3m cubic (QPn3m) phase, known as the OBDD, indicate that it is an unstable structure in diblock melts. Earlier approximation schemes used to examine mean-field behavior are reviewed, and compa...

1,256 citations

Posted Content
TL;DR: It is shown that a system with competing interactions on different length scales, relevant to the formation of stripes in doped Mott insulators, undergoes a self-generated glass transition which is caused by the frustrated nature of the interactions and not related to the presence of quenched disorder.
Abstract: Using our previous results for the configurational entropy of a stripe glass as well as a variational result for the bare surface tension of entropic droplets we show that there is no disagreement between the numerical simulations of Grousson et al. and our theory. The claim that our theory disagrees with numerical simulations is based on the assumption that the surface tension is independent of the frustration parameter Q of the model. However, we show in this Reply that it varies strongly with Q and that the resulting Q-dependence of the kinetic fragility agrees with the one obtained by Grousson et al. We believe that this answers the questions raised in the Comment by Grousson et al.

127 citations

Journal ArticleDOI
TL;DR: In this paper, eine Einfiihrung in einige aktuelle Forschungsaspekte aus dem Bereich der Biophysik zu geben is discussed.
Abstract: Das Ziel dieses Buches ist es, eine Einfiihrung in einige aktuelle Forschungsaspekte aus dem Bereich der Biophysik zu geben. Der Inhalt des Buches umfaBt folgende Teilgebiete: den Einsatz der Mikrolithographie zur DNA-Trennung, die Modellierung der Faltung, Struktur und Dynamik von Proteinen, neuere theoretische Ansátze zur Proteinfaltung, die Physik der Organellen, Mechanismen molekularer Motorén, die Dynamik von Mikrotubuli, Formübergange und Fluktuationen von Membránén, Vesikeln und Zellen, die Biophysik des Gehirns und seiner Neuronen, weiterhin werden die sensorische Signalverarbeitung, molekulare evolutionsbiologische Strategien und potentielle Anwendungen, die Musterbildung beim Wachstum bakterieller Kolonien und Evolutionsmodelle erotteti. Das Buch, das aus einer Sommerschule und einem Workshop hervorgegangen ist, richtet sich an fortgeschrittene Studenten und an Doktoranden der Physik, Chemie und Biologie (z.T. sind mathematische Kenntnisse erforderlich!), aber auch an Forscher, die sich mit biophysikalischen Fragestellungen beschaftigen und einen aktuellen Einstieg in die angesprochenen modernen Forschungsfelder der Biophysik suchen. Die Artikel sind

18 citations

Journal Article
TL;DR: The selectivity of cell-cell and cell-tissue adhesion is determined by specific short range forces between cell surface proteins, which function as constraint reaction spaces facilitating the local assembly of actin stress fibers and control cell signalling processes.
Abstract: The selectivity of cell-cell and cell-tissue adhesion is determined by specific short range forces between cell surface proteins. Long range entropic interfacial forces (mediated by repeller molecules and membrane undulations) and adhesion-induced elastic stresses in the cell envelope serve the fine control of the strength and duration of adhesion. The initial step of cell adhesion exhibits typical features of a first order wetting transition resulting in the formation of tight adhesion domains by lateral phase separation of receptors. External lift forces can cause shrinking and unbinding of adhesion sites if the receptors are immobile but induce domain growth if they are mobile. Strong adhesion domains (resisting nano-Newton forces) can form by commitment of some 10,000 receptors enabling cells to control adhesion strength rapidly by varying the receptor and repeller densities on cell surfaces through endocytosis and exocytosis. The adhesion domains can function as constraint reaction spaces facilitating the local assembly of actin stress fibers and control cell signalling processes as shown for the activation of immunological responses by immunological synapses.

12 citations

References
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Journal ArticleDOI
TL;DR: In this article, the structure and thermodynamics of the critical nuclei in metastable binary polymer blends using the self-consistent field method were studied and the results were valid throughout the entire metastable region and provided a smooth crossover from the classical capillary-theory predictions near the coexistence curve to the density functional predictions of Cahn and Hilliard near the spinodal.
Abstract: We study the structure and thermodynamics of the critical nuclei in metastable binary polymer blends using the self-consistent field method. At the mean-field level, our results are valid throughout the entire metastable region and provide a smooth crossover from the classical capillary-theory predictions near the coexistence curve to the density functional predictions of Cahn and Hilliard (properly transcribed into expressions involving the parameters of the binary polymer blends) near the spinodal. An estimate of the free energy barrier provides a quantitative criterion (the Ginzburg criterion) for the validity of the (mean-field) self-consistent approach. The region where mean-field theory is valid and where there can be a measurable nucleation rate is shown to be poorly described by the existing limiting theories; our predictions are therefore most relevant in this region. We discuss our results in connection with recent experimental observations by Balsara and co-workers.

67 citations

Journal ArticleDOI
TL;DR: In this article, a modele simple for decrire la coexistence de la gelification and d'une phase de demixtion dans des solutions de polystyrene atactique is described.
Abstract: Description d'un modele simple pour decrire la coexistence de la gelification et d'une phase de demixtion dans des solutions de polystyrene atactique

66 citations


"Interplay Between Long-Range And Sh..." refers methods or result in this paper

  • ...Based on this model, Tanaka and co-workers (Tanaka, 1989, 1990; Tanaka and Matsuyama, 1989; Tanaka and Stockmayer, 1994) extended the model by Coniglio et al. (1982) to study the thermodynamics of reversible gelation....

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  • ...We recover the phase diagram as observed in Tanaka et al. (1979) and obtained in the papers by Coniglio et al. (1982), Tanaka (1989), and Semenov and Rubinstein (1998a), but the gelation line is identified as the microphase transition spinodal with no a priori assumption of the network....

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  • ...The phase diagram is very similar to the experimental results obtained for gelatin solution by Tanaka et al. (1979) and theoretical calculations by Tanaka (1989) and by Semenov and Rubinstein (1998a)....

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Journal ArticleDOI
TL;DR: It is demonstrated that two-dimensional binding rates between receptor and ligand can be lower than three dimensional on rates by orders of magnitude due to reduced accessibility of the immobilized protein.
Abstract: We experimentally studied the adhesion dynamics of vesicles decorated with specific stickers onto bioactive surfaces. The growth laws were found to strongly depend upon the chemical preparation of the substrate and were rationalized with theoretical descriptions based on scaling law arguments. By using a micropipette-free approach, we demonstrate that two-dimensional binding rates between receptor and ligand can be lower than three dimensional on rates by orders of magnitude due to reduced accessibility of the immobilized protein.

66 citations


"Interplay Between Long-Range And Sh..." refers background in this paper

  • ..., 2005), vesicles or liposomes (Cuvelier et al., 2004; Cuvelier and Nassoy, 2004), and substrate-supported monolayer and bilayer membranes (Sackmann, 1996; Tanaka and Sackmann, 2005) allow better characterization of the specific and non-specific interactions because of the absence of complicating factors such as chemical signaling and deformability of biological cells in vivo (Lawrence and Springer, 1991; Dustin et al....

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Journal ArticleDOI

65 citations


"Interplay Between Long-Range And Sh..." refers background in this paper

  • ...Furthermore, the simulation results by Kumar and co-workers (Kumar and Panagiotopoulos, 1999; Kumar and Douglas, 2001) showed that for associating polymers with weak connections (associating energy comparable to kBT ), gelation is characterized by a change of dynamic properties, which marks a distinct transition line from the percolation transition....

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  • ...Kumar and co-workers (Kumar and Panagiotopoulos, 1999; Kumar and Douglas, 2001) conducted Monte Carlo simulations on the phase behavior and gelation of reversibly associating polymers....

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  • ...Furthermore, the simulation results by Kumar and co-workers (Kumar and Panagiotopoulos, 1999; Kumar and Douglas, 2001) showed that for associating polymers with weak connections (associating energy comparable to kBT ), gelation is characterized by a change of dynamic properties, which marks a…...

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Journal ArticleDOI
TL;DR: In this paper, an expression for the free energy of the blends of block copolymers expressed as a functional of the density distribution of the monomer of each block was derived, which is a generalization of the Flory−Huggins−de Gennes theory for homopolymer blends.
Abstract: We derive an expression for the free energy of the blends of block copolymers expressed as a functional of the density distribution of the monomer of each block. The expression is a generalization of the Flory−Huggins−de Gennes theory for homopolymer blends and also a generalization of the Ohta−Kawasaki theory for the melts of diblock copolymers. The expression can be used for any blends of homopolymers and block copolymers of any topological structure. The expression gives a fast and stable computational method to calculate the micro- and macro-phase separation of the blends of homopolymers and block copolymers.

64 citations


"Interplay Between Long-Range And Sh..." refers background in this paper

  • ...Further extensions such as the dynamic density functional theory by Fraaije et al. (1997) and Uneyama and Doi (2005) allow systematic studies of the phase separation kinetics in these systems....

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