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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
02 Aug 1990-Nature
TL;DR: Three families of cell-surface molecules regulate the migration of lymphocytes and the interactions of activated cells during immune responses.
Abstract: The adhesive interactions of cells with other cells and with the extracellular matrix are crucial to all developmental processes, but have a central role in the functions of the immune system throughout life Three families of cell-surface molecules regulate the migration of lymphocytes and the interactions of activated cells during immune responses

6,595 citations


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

  • ...Cell adhesion is crucial to many biological processes, including cell differentiation and division, signal transduction, and immunological responses (Alberts et al., 2002; Berg et al., 2002; Springer, 1990)....

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  • ...The average tether length (contour length) of integrins and selectins on lymphocyte cells is of order 10nm (Springer, 1990), which is comparable to the estimation in the Bell papers (Bell, 1978; Bell et al....

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Journal ArticleDOI
TL;DR: In this paper, a molecularkinetic theory was proposed to explain the temperature dependence of relaxation behavior in glass-forming liquids in terms of the temperature variation of the size of the cooperatively rearranging region.
Abstract: A molecular‐kinetic theory, which explains the temperature dependence of relaxation behavior in glass‐forming liquids in terms of the temperature variation of the size of the cooperatively rearranging region, is presented. The size of this cooperatively rearranging region is shown to be determined by configuration restrictions in these glass‐forming liquids and is expressed in terms of their configurational entropy. The result of the theory is a relation practically coinciding with the empirical WLF equation. Application of the theory to viscosimetric experiments permits evaluation of the ratio of the kinetic glass temperature Tg (derived from usual ``quasistatic'' experiments) to the equilibrium second‐order transition temperature T2 (indicated by either statistical‐mechanical theory or extrapolations of experimental data) as well as the hindrance‐free energy per molecule. These parameters have been evaluated for fifteen substances, the experimental data for which were available. Hindrance‐free energies ...

5,037 citations


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

  • ...TK is often termed the ideal glass transition temperature and is conceptually identified with the underlying thermodynamic glass transition at which the viscosity of the supercooled liquid diverges (Kauzmann, 1948; Adam and Gibbs, 1965; Monasson, 1995; Debenedetti and Stillinger, 2001)....

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  • ...The central assumption in the thermodynamic approach is that the dynamic behavior of glassforming systems reflects the underlying free-energy-landscape features (Adam and Gibbs, 1965; Kirkpatrick et al., 1989; Monasson, 1995; Coluzzi et al., 2000; Debenedetti and Stillinger, 2001)....

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Journal ArticleDOI
TL;DR: A theory of the elasticity of lipid bilayers is proposed and it is argued that in the case of vesicles (= closed bilayer films) the only elasticity controlling nonspherical shapes is that of curvature.

4,853 citations

Book
15 Aug 2002
TL;DR: In this paper, a renormalization group analysis is proposed to model the scaling behavior of a field theory in the large N limit of the ferromagnetic order at low temperature.
Abstract: Algebraic preliminaries Euclidean path integrals in quantum mechanics Path integrals in quantum mechanics - generalizations stochastic differential equations - Langevin, Fokker-Planck equations functional integrals in field theory generating functionals of correlation functions - loopwise expansion divergences in pertubation theory, power counting regularization methods introduction to renormalization theory - renormalization group equations dimensional regularization and minimal subtraction - calculation of RG functions renormalization of composite operators - short distance expansion linearly realized symmetries and renormalization non linearly realized symmetries - the examples of the non linear sigma-model models on homogeneous spaces in two dimensions tensorial analysis on Riemannian manifolds symmetric spaces - non local conservation laws, renormalization group Slavnov-Taylor and BRS symmetry - stochastic field equations renormalization and stochastic field equations - supersymmtery Abelian gauge theories non-Abelian gauge theories the standard model - anomalies renormalization of gauge theories - general formalism critical phenomena - general considerations mean field theory for ferromagnetic systems general renormalization group analysis - the critical theory near dimension four scaling behaviour in the critical domain corrections to scaling behaviour calculation of universal quantities the (phi squared) squared field theory in the large N limit ferromagnetic order at low temperature - the non linear sigma-model a few two-dimensional models - bosonization technique the 0 (2) non linear sigma-model critical properties of gauge theories large momentum behaviour in field theory critical dynamics field theory in a finite geometry - finite size scaling instantons in quantum mechanics - the anharmonic oscillator quantum mechanics - generalization unstable vacua in field theory degenerate classical minima and instantons perturbation theory at large orders and instantons - the summation problem the "phi to the fourth" field theory in dimension four fermions and large order behaviour multi-instantons in quantum mechanics

4,335 citations


Additional excerpts

  • ...…the expansion of F0(φα), F0(ϕα + φ̄α)− F0(φ̄α) = 1 β ∑ m>1 Γ(m)α1α2···αmϕα1ϕα2 · · ·ϕαm , (2.24) the vertex functions are related to the amputated connected correlation functions (Zinn-Justin, 2002): Γ(2)αβ(x1,x2) = Sαβ(x1,x2) = [ G(2)c (x1,x2) ]−1 αβ ; (2.25a) Γ(3)αβγ(x1,x2,x3) = −G (3)…...

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Journal ArticleDOI
12 May 1978-Science
TL;DR: The force required to separate two cells is shown to be greater than the expected electrical forces between cells, and of the same order of magnitude as the forces required to pull gangliosides and perhaps some integral membrane proteins out of the cell membrane.
Abstract: A theoretical framework is proposed for the analysis of adhesion between cells or of cells to surfaces when the adhesion is mediated by reversible bonds between specific molecules such as antigen and antibody, lectin and carbohydrate, or enzyme and substrate. From a knowledge of the reaction rates for reactants in solution and of their diffusion constants both in solution and on membranes, it is possible to estimate reaction rates for membrane-bound reactants. Two models are developed for predicting the rate of bond formation between cells and are compared with experiments. The force required to separate two cells is shown to be greater than the expected electrical forces between cells, and of the same order of magnitude as the forces required to pull gangliosides and perhaps some integral membrane proteins out of the cell membrane.

4,058 citations