scispace - formally typeset
Search or ask a question
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.

Content maybe subject to copyright    Report

Citations
More filters
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
More filters
Journal ArticleDOI
TL;DR: A model system to study the control of cell adhesion by receptor-mediated specific forces, universal interactions, and membrane elasticity is established by reconstitution of homophilic receptor proteins into solid supported membranes and into giant vesicles with the polymers forming an artificial glycocalix.

155 citations


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

  • ...The adhesion process proceeds in three steps (Albersdörfer et al., 1997; Kloboucek et al., 1999; Boulbitch et al., 2001; Sackmann and Bruinsma, 2002)....

    [...]

  • ...4) have been measured by Sackmann and co-workers in different systems (see Flyvbjerg et al., 1997; Simson et al., 1998; Kloboucek et al., 1999; Bruinsma and Sackmann, 2002; Sackmann, 2006; Sackmann and Goennenwein, 2006)....

    [...]

Journal ArticleDOI
TL;DR: Etude theorique de la separation microphase de copolymeres bisequences en solution concentree et semidiluee as discussed by the authors is based on the separation theory.
Abstract: Etude theorique de la separation microphase de copolymeres bisequences en solution concentree et semidiluee

151 citations


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

  • ...In fact, it is believed that in copolymer solutions with non-selective solvents, the microphase transition is likened to the ordering transition in copolymer melt with “diluted” monomer interactions (Fredrickson and Leibler, 1989)....

    [...]

Journal ArticleDOI
TL;DR: In this paper, reflection interference contrast microscopy (RICM) was used to map the optical density of supported bilayers and vesicles and image the contact profile of phospholipid vicles at surfaces.
Abstract: We present the application of reflection interference contrast microscopy (RICM) (1) to map the optical density of supported bilayers and vesicles and (2) to image the contact profile of phospholipid vesicles at surfaces. The resolution in the surface profile is 0.2 $\mu$m laterally and 1 nm out of plane. The optical thickness of the membrane can be determined with 0.2 nm accuracy. We outline the theoretical basis of RICM and derive the interference intensities of adhering vesicles from first principles. An analytical expression for the decaying contrast of the intrference fringes is given. The contact contour of vesicles is determined for various substrates. We further demonstrate that deposition of a magnesium fluoride layer on the glass substrate enhances the contrast and allows the optical density of adsorbed membranes to be imaged. By contrast variation of the buffer solution, the layer thicknesses and the indices of refraction can be measured. The novel method was applied to image lipid domains of different chain lengths in a substrate supported monolayer.

148 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the model of a randomly-sited solution of dipoles with distance-dependent and hence randomly-signed forces to study dilute magnetic alloys.
Abstract: For pt.I see ibid., vol.5, p.965 (1975). The paper continues the study of dilute magnetic alloys using the model of a randomly-sited solution of dipoles with distance-dependent and hence randomly-signed forces. The time dependence of the system is studied above and below the critical temperature and the self-correlation time of a dipole is shown to tend to infinity as T to Tc from above. Comparable results are obtained from below, where it is shown that the system settles into one of many states of equilibrium. The behaviour near T=0 is shown to be dominated by domain structure.

146 citations


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

  • ..., the Edwards-Anderson order parameter defined as the long-time spin-spin correlation function in the Ising-spin-glass model (Edwards and Anderson, 1976)) and characterizes the glassy state with non-vanishing long-time correlations and broken ergodicity....

    [...]

  • ...…on dynamic correlation functions (e.g., the Edwards-Anderson order parameter defined as the long-time spin-spin correlation function in the Ising-spin-glass model (Edwards and Anderson, 1976)) and characterizes the glassy state with non-vanishing long-time correlations and broken ergodicity....

    [...]