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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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
554 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
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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TL;DR: It is found that the Langevin dynamics of the soft-spin, continuum version of the Coulomb-frustrated Ising ferromagnet displays a transition from an ergodic to a nonergodic behavior similar to that obtained in the idealized mode-coupling theory of glass-forming liquids.
Abstract: We study the Langevin dynamics of the soft-spin, continuum version of the Coulomb-frustrated Ising ferromagnet. By using the dynamical mode-coupling approximation, supplemented by reasonable approximations for describing the equilibrium static correlation function, and the somewhat improved dynamical self-consistent screening approximation, we find that the system displays a transition from an ergodic to a nonergodic behavior. This transition is similar to that obtained in the idealized mode-coupling theory of glass-forming liquids and in the mean-field generalized spin glasses with one-step replica symmetry breaking. The significance of this result and the relation to the appearance of a complex free-energy landscape are also discussed.
23 citations
Additional excerpts
...Similar conclusions were also obtained by Grousson et al. (2002a) 36 using the mode-coupling theory....
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TL;DR: In this article, grain growth in polystyrene and polyisoprene block copolymer melt is studied by time-resolved depolarized light scattering after a quiescent quench from the disordered to the ordered state.
Abstract: Grain growth in a polystyrene–polyisoprene block copolymer melt is studied by time-resolved depolarized light scattering after a quiescent quench from the disordered to the ordered state. At shallow quench depths, classical nucleation and growth kinetics are observed. Grains comprising the equilibrated ordered phase nucleate and grow by consuming the surrounding disordered phase. In contrast, deep quenches result in the formation of disorganized grains with an average order parameter that is well below the equilibrium value. Small angle neutron scattering and rheological experiments were conducted to facilitate the interpretation of the light scattering data. We show that the nonequilibrium grain structure formed during deep quenches is due to extremely high nucleation density. Under these circumstances, the space required for the formation of equilibrated grains is unavailable.
23 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...Balsara and co-workers (Balsara et al., 1998; Kim et al., 2001) studied the grain structure of asymmetric, hex-forming PI-PS (polyisoprene–polystyrene) melt by light scattering, SANS, and rheological measurements....
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TL;DR: It is shown by means of a Monte Carlo simulation study that three-dimensional models with long-range frustration display the generic phenomena seen in fragile glass-forming liquids.
Abstract: We show by means of a Monte Carlo simulation study that three-dimensional models with long-range frustration display the generic phenomena seen in fragile glass-forming liquids. Due to their properties (absence of quenched disorder, physical motivation in terms of structural frustration, and tunable fragility), these systems appear as promising minimal theoretical models for describing the glass transition of supercooled liquids.
22 citations
"Interplay Between Long-Range And Sh..." refers methods in this paper
...Similar conclusions were also obtained by Grousson et al. (2002a) 36 using the mode-coupling theory....
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TL;DR: In this paper, the tendency towards microphase separation in microemulsions can lead to the formation of a glassy state after sufficiently strong correlations between polar and hydrophobic regions have been established.
22 citations
TL;DR: In this article, phase transitions in sphere-forming polystyrene block copolymers were investigated using oscillatory shear rheometry, transmission electron microscopy, and small-angle X-ray scattering (SAXS).
Abstract: Phase transitions in sphere-forming polystyrene-block-polyisoprene-block-polystyrene (SIS triblock) copolymer and its blends with polystyrene (PS) were investigated using oscillatory shear rheometry, transmission electron microscopy, and small-angle X-ray scattering (SAXS). For the investigation, a commercial grade of high-molecular-weight SIS triblock copolymer (Vector 4113, Dexco Polymers) and a low-molecular-weight SIS triblock copolymer (SIS-100) synthesized in our laboratory were used. It is found from oscillatory shear rheometry and SAXS that both Vector 4113 and SIS-100 undergo order−disorder transition (ODT) having a characteristic feature of lattice disordering/ordering transition (LDOT) of spheres, giving rise to a phase consisting of micelles with short-range liquidlike order at thermal equilibrium above ODT and demicellization/micellization transition (DMT), as a pseudo phase transition, giving rise to a micelle-free phase with only thermal composition fluctuations. The LDOT temperature (TLDOT...
21 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...The most dramatic manifestation of the first step is the existence of disordered-spherical-micelle state in highly asymmetric copolymer melts, which almost has the appearance of a distinct phase between the featureless disordered phase and the bcc-ordered phase (Adams et al., 1994, 1996; Schwab and Stühn, 1996; Kim et al., 1999; Han et al., 2000; Sota et al., 2003; Choi et al., 2003; Wang et al., 2002)....
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...…highly asymmetric copolymer melts, which almost has the appearance of a distinct phase between the featureless disordered phase and the bcc-ordered phase (Adams et al., 1994, 1996; Schwab and Stühn, 1996; Kim et al., 1999; Han et al., 2000; Sota et al., 2003; Choi et al., 2003; Wang et al., 2002)....
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...However, experiments show that between the featureless disordered phase and the ordered bcc phase, there exists an intervening disordered-micelle state (Adams et al., 1994, 1996; Schwab and Stühn, 1996; Kim et al., 1999; Han et al., 2000; Sota et al., 2003; Choi et al., 2003; Wang et al., 2002; Semenov, 1989; Dormidontova and Lodge, 2001)....
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