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DissertationDOI

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

01 Jan 2008-

AbstractInterplay 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.

Topics: Membrane bending (56%), Adhesion (52%)

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Citations
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01 Mar 1996
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...

1,191 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.

121 citations


Journal ArticleDOI
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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Book
01 Jan 1985
Abstract: The Forces between Atoms and Molecules. Principles and Concepts. Historical Perspective. Some Thermodynamic Aspects of Intermolecular Forces. Strong Intermolecular Forces: Covalent and Coulomb Interactions. Interactions Involving Polar Molecules. Interactions Involving the Polarization of Molecules. van der Waals Forces. Repulsive Forces, Total Intermolecular Pair Potentials, and Liquid Structure. Special Interactions. Hydrogen-Bonding, Hydrophobic, and Hydrophilic Interactions. The Forces between Particles and Surfaces. Some Unifying Concepts in Intermolecular and Interparticle Forces. Contrasts between Intermolecular, Interparticle, and Intersurface Forces. van der Waals Forces between Surfaces. Electrostatic Forces between Surfaces in Liquids. Solvation, Structural and Hydration Forces. Steric and Fluctuation Forces. Adhesion. Fluid-Like Structures and Self-Assembling Systems. Micelles, Bilayers, and Biological Membranes. Thermodynamic Principles of Self-Assembly. Aggregation of Amphiphilic Molecules into Micelles, Bilayers, Vesicles, and Biological Membranes. The Interactions between Lipid Bilayers and Biological Membranes. References. Index.

18,041 citations


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

  • ..., 2006; Moore and Kuhl, 2006; Moreira and Marques, 2004; Sain and Wortis, 2004), and suggests a new route to controlling the interactions between surfaces typically achieved by generic physical interactions (Israelachvili, 1992; Hiddessen et al., 2000; Carignano and Szleifer, 2003; Nap and Szleifer, 2005)....

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  • ...The interplay between specific and other generic physical interactions, such as electrostatic, hydrophobic and steric interactions (Israelachvili, 1992), is crucial to the adhesion and signalling between cells and the extracellular matrix, and has been extensively studied by researchers in physiology, biochemistry, biophysics, and bioengineering (Alberts et al....

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Book
01 Jan 1953

16,813 citations


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

  • ...Near the mean-field spinodal γ2(q,−q) can be approximated as γ2(q,−q) = c2 4 ( q2Nb2 − q2mNb2 )2 + 2 (χN)S − 2χN, where χN is the Flory-Huggins interaction parameter between A and B blocks, (χN)S is its value at the spinodal, and c is a parameter independent of N ....

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  • ...It was Flory (1953) who first calculated the amount of crosslinkers that are necessary to generate a macroscopic network (Flory-Stockmayer model) and studied the elasticity of this network (“rubber elasticity” theory)....

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  • ...In the classical model by Flory and Stockmayer (see Flory, 1953), the crosslinked network (e.g., vulcanized rubber) is assumed to be an infinitely large branched tree (without cycles), which is the mean-field limit of the percolation model (i.e., percolation on a Cayley tree)....

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  • ...The polymer solution is treated following the mean-field theory of Flory and Huggins (Flory, 1953) and the reversible gelation is treated as a micellation....

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Book
15 Dec 1979

10,758 citations


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

  • ...Such polyfunctional units are interconnected 1An exception is the network generated by topological entanglements, such as in melts of very long polymer chains, or a series of interconnected rings (de Gennes, 1979)....

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  • ...Furthermore, as each crosslinker (multi-functional unit) is surrounded by many monomers, cycle structures are rare, therefore the Flory-Stockmayer model is accurate even near the critical threshold (de Gennes, 1979)....

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Book
01 Jan 1986
Abstract: Introduction Static properties of polymers Brownian motion Dynamics of flexible polymers in dilute solution Many chain systems Dynamics of a polymer in a fixed network Molecular theory for the viscoelasticity of polymeric liquids Dilute solutions of rigid rodlike polymers Semidilute solutions of rigid rodlike polymers Concentrated solutions of rigid rodlike polymers Index.

10,219 citations


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

  • ...Second, we construct the mean-field phase diagram through a quadratic expansion of the free energy (effective potential) from the Edwards Hamiltonian....

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  • ...A continuum Gaussian chain with length N in an external field V (r) is described by the Edwards Hamiltonian (Doi and Edwards, 1986) h0[R(t)] = 3kBT 2Nb2 ∫ 1 0 [( ∂R(t) ∂t )2 + V (R(t)) ] dt (2.1) where R(t) maps the configuration of the polymer (0 ≤ t ≤ 1 is a parametrization of the polymer chain), and Nb2 is mean square end-to-end distance....

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  • ...A continuum Gaussian chain with length N in an external field V (r) is described by the Edwards Hamiltonian (Doi and Edwards, 1986) h0[R(t)] = 3kBT 2Nb2 ∫ 1 0 [( ∂R(t) ∂t )2 + V (R(t)) ] dt (2.1) where R(t) maps the configuration of the polymer (0 ≤ t ≤ 1 is a parametrization of the polymer chain),…...

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  • ...Using the Green’s function for Gaussian chains (Doi and Edwards, 1986) we can express the partition function qp as qp = ∫ G(r, r′;N), where G(r, r′;N) satisfies [ ∂ ∂N − b 2 6 ∇2r +W (r) ] G(r, r′;N) = δ(r− r′)....

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