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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01 Jan 1982
TL;DR: For the critical exponents near the sol-gel phase transition, classical theories like those of Flory and Stockmayer predict one set of exponents, whereas scaling theories based on lattice percolation predict different exponents as discussed by the authors.
Abstract: For the critical exponents near the sol-gel phase transition, classical theories like those of Flory and Stockmayer predict one set of exponents, whereas scaling theories based on lattice percolation predict different exponents. The two groups of theories differ in their treatment of intramolecular loops, space dimensionality and excluded volume effects. In this article, the differences and similarities between the results of the competing theories are reviewed. For example, a gel fraction like (p-pc)β vanishes for conversion factors p very close to the gel point pc, the weight average molecular weight diverges as (pc-p)−γ for p very slightly below pc, and the radius of macromolecules at the gel point p=pc varies as the ϱ-th power of the number of monomers in that macromolecule. Classical theories predict β=γ=1 and ϱ=1/4 whereas the percolation theory gives β ≃ 0.45, γ ≃ 1.74 and ϱ ≃ 0.40. We also generalize the percolation concept to include interaction effects and concentration fluctuations; in this case the sol-gel phase transition may be connected with a phase separation.
695 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...Sol-gel transition is a natural example of percolation (Stauffer et al., 1982), which is characterized by the emergence of a macroscopic cluster....
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Book•
11 Jan 1996
665 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...A typical example is vulcanized rubber, where sulphur molecules act as the crosslinking agents (Doi, 1996)....
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TL;DR: A thermodynamic calculus for the modeling of cell adhesion is developed, able to compute the end results of competition between the formation of specific macromolecular bridges and nonspecific repulsion arising from electrostatic forces and osmotic (steric stabilization) forces.
662 citations
TL;DR: In this article, a class of new computer simulation methods for polymeric fluids and other soft condensed matter systems that are based on an underlying field-theoretic description are presented.
Abstract: We review a class of new computer simulation methods for polymeric fluids and other soft condensed matter systems that are based on an underlying field-theoretic description. These methods, while still in an early stage of development, show considerable promise for studying the equilibrium properties of many-component systems capable of intricate self-assembly, such as solutions and blends containing block and graft copolymers. Field-theoretic simulation methods also provide a great deal of flexibility in model building and coarse graining, and appear to be particularly well suited to treat systems with soft, long-range interactions, such as polyelectrolytes. We attempt to connect various related theoretical approaches, such as self-consistent field theory and dynamic density functional theory, within a common framework.
646 citations
"Interplay Between Long-Range And Sh..." refers background or methods in this paper
...To calculate qp, we only need q(r, l), the once-integrated Green’s function (propagator) (see Wood and Wang, 2002; Tzeremes et al., 2002; Drolet and Fredrickson, 1999; Fredrickson et al., 2002)...
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...Many results are summarized in the reviews by Schmid (1998) and by Fredrickson et al. (2002)....
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...[See Fraaije et al. (1997), or the reviews, Schmid (1998) and Fredrickson et al. (2002), for examples of irregular morphologies.]...
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...…only need q(r, l), the once-integrated Green’s function (propagator) (see Wood and Wang, 2002; Tzeremes et al., 2002; Drolet and Fredrickson, 1999; Fredrickson et al., 2002) q(r, l) = ∫ G(r, r′; l)dr′, which satisfies the same diffusion equation as G(r, r′) [ ∂ ∂l − b 2 6 ∇2r + ∑ α δα(l)Wα (r) ]…...
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Book•
01 Jan 2004
TL;DR: The Statistical Mechanics of Membranes and Interfaces (D Nelson) Interfaces: Fluctuations, Interactions and Related Transitions (M E Fisher) Equilibrium statistical mechanics of Fluctuating Films and Membrane (S Leibler) The Physics of Microemulsions and Amphiphilic Monolayers (D Andelman) Properties of Tethered Surfaces (Y Kantor) Theory of the Crumpling Transition as mentioned in this paper.
Abstract: The Statistical Mechanics of Membranes and Interfaces (D Nelson) Interfaces: Fluctuations, Interactions and Related Transitions (M E Fisher) Equilibrium Statistical Mechanics of Fluctuating Films and Membranes (S Leibler) The Physics of Microemulsions and Amphiphilic Monolayers (D Andelman) Properties of Tethered Surfaces (Y Kantor) Theory of the Crumpling Transition (D Nelson) Geometry and Field Theory of Random Surfaces and Membranes (F David) Statistical Mechanics of Self-Avoiding Crumpled Manifolds (B Duplantier) Anisotropic and Heterogeneous Polymerized Membranes (L Radzihovsky) Fixed-connectivity Membranes (M Bowick) Triangulated Surface Models of Fluctuating Membranes (G Gompper & D Kroll)
626 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...Many different interactions are involved in adhesions in vivo: lock-and-key type interactions between proteins (Lauffenburger and Linderman, 1993), force-induced signaling, reorganization of actin filaments and the cortex (Lipowsky, 1995), and various generic physical forces (Nelson et al., 2004)....
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...These fluctuation effects have been extensively studied (Nelson et al., 2004); in particular, membrane fluctuations induce an effective repulsion which contributes to V [z(r)]....
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