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.
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References
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114 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...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., 2002; Bongrand, 1999; Hammer and Tirrell, 1996; Orsello et al., 2001; Zhu et al., 2000; Baudry et al., 2004; Cuvelier et al., 2004)....
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TL;DR: In this paper, a theory for concentration fluctuations in binary polymer blends is developed using field-theoretic techniques, and a unified Ginzburg criterion involving both the composition and temperature (or temperaturelike variable) is derived that is applicable to both the critical and the off-critical spinodal regimes.
Abstract: A theory for concentration fluctuations in binary polymer blends is developed using field-theoretic techniques. The theory provides a simple, unified framework for addressing a number of important issues. First, consideration of the fluctuation and correlation effects on different length scales leads to a clarification of three different chi parameters and their interrelationship. By incorporating interaction (modeled by the bare χb) and packing effects up to the polymer size, an effective chie emerges as the natural parameter for characterizing the molecular compatibility of the two polymer species. The measured quantity in small-angle neutron scattering (SANS) experiments is an apparent chia that includes long wavelength critical and spinodal fluctuations, and is related to χe through a self-consistent equation. χa exhibits the typical upward parabolic composition dependence observed in experiments and computer simulations. Second, a unified Ginzburg criterion involving both the composition and temperature (or temperaturelike variable) is derived that is applicable to both the critical and the off-critical spinodal regimes. The common characterization of the Ginzburg criterion in terms of a range of temperature (or temperaturelike variable) alone is generally inadequate. The molecular weight scaling proposed by de Gennes and Binder in the respective critical and off-critical spinodal regimes are recovered as special cases in the limit of large molecular weights. For typical molecular weights used in experiments the Ginzburg region is larger than commonly believed. Finally, the nature of the thermodynamic spinodal is examined. It is shown that a true off-critical thermodynamic spinodal does not exist in spatial dimensions less than 4. In its place, a pseudo-spinodal can be defined where the susceptibility reaches a finite maximum. The pseudo-spinodal precedes the mean-field spinodal but approaches the latter in the limit of infinite molecular weights. The pseudo-spinodal correlates strongly with the free energy barrier for nucleation becoming order kT. Thus it provides a kinetic limit for the physically accessible metastable state, beyond which phase separation may exhibit features characteristic of spinodal decomposition. The calculated location of the pseudo-spinodal for two samples used in a recent experiment of Balsara and co-workers agrees with the onset of spinodal-decomposition-like nucleation observed in the experiment.
110 citations
TL;DR: In this article, three distinct tilt grain boundary morphologies were observed: the chevron, the omega boundary, and the T-junction, and a transition from either the cheveron or the Omega boundary to the T junction occurs as the boundary becomes more asymmetric.
Abstract: Tilt grain boundaries in poly(styrene-b-butadiene) lamellar diblock copolymers were characterized using transmission electron microscopy (TEM). Three distinct tilt grain boundary morphologies were observed: the chevron, the omega boundary, and the T-junction. All three boundary types are found to have intermaterial dividing surfaces, separating the polystyrene and polybutadiene microphases, that approximate surfaces of constant mean curvature. The chevron and omega morphologies are observed for symmetric tilt boundaries, and a transition occurs from the chevron to the omega as tilt is increased at constant boundary width. A transition from either the chevron or the omega boundary to the T-junction occurs as the boundary becomes more asymmetric
105 citations
"Interplay Between Long-Range And Sh..." refers background or methods in this paper
...Experimentally these structures have been identified using transmission electron microscopy (TEM) (Bates et al., 1982; Gido and Thomas, 1994), small-angle neutron scattering (SANS) (Bates et al....
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...Experimentally these structures have been identified using transmission electron microscopy (TEM) (Bates et al., 1982; Gido and Thomas, 1994), small-angle neutron scattering (SANS) (Bates et al., 1982, 1990; Almdal and Bates, 1992), and dynamic mechanical measurements (Bates et al., 1990; Rosedale and Bates, 1990; Almdal and Bates, 1992)....
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...Experimentally these structures have been identified using transmission electron microscopy (TEM) (Bates et al., 1982; Gido and Thomas, 1994), small-angle neutron scattering (SANS) (Bates et al., 1982, 1990; Almdal and Bates, 1992), and dynamic mechanical measurements (Bates et al., 1990; Rosedale…...
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TL;DR: The past several years have seen accelerating growth in research directed towards the understanding and control of cell adhesion processes, from a spectrum of disciplinary approaches including molecular cell biology, biochemistry, biophysics and bioengineering.
103 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...First, the equilibrium constant in the Bell model is by definition for a chemical reaction in two dimensions (2D), which can only be inferred from measurements in bulk solutions (3D), but the relation between these two equilibrium constants is obscure and often causes confusion (Dustin et al., 1996; Orsello et al., 2001; Zhu et al., 2000)....
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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., 2002; Bongrand, 1999; Hammer and Tirrell, 1996; Orsello et al., 2001; Zhu et al., 2000; Baudry et al., 2004; Cuvelier et al., 2004)....
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...These results clarify the persistent confusion about the interpretation of experimental measurements of binding affinity (Dustin et al., 1996; Orsello et al., 2001)....
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98 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...The micelle state was first predicted by Semenov (1989)....
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