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
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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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TL;DR: A numerical implementation of self-consistent mean-field theory for the structural phase behavior of block copolymers with significant architectural complexity is proposed and illustrated by applying it to a triblock copolymer system.
Abstract: A numerical implementation of self-consistent mean-field theory for the structural phase behavior of block copolymers is proposed. Our scheme does not require a priori assumptions of the underlying mesoscopic symmetries. The method potentially enables us to characterize, with high accuracy, the structural phase diagram of block copolymers with significant architectural complexity. We illustrate the method by applying it to a triblock copolymer system.
277 citations
"Interplay Between Long-Range And Sh..." refers methods in this paper
...From the Baker-Hausdorff operator identity (Tzeremes et al., 2002),...
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...We adopt the following iteration scheme (Drolet and Fredrickson, 2001; Tzeremes et al., 2002): 1....
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...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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...(2.30) 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) q(r, l) = ∫ G(r, r′; l)dr′, which satisfies the same diffusion equation as G(r, r′) [ ∂ ∂l − b 2 6…...
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...We adopt the following iteration scheme (Drolet and Fredrickson, 2001; Tzeremes et al., 2002): 1....
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TL;DR: In this article, a new model for polymer gelation is presented that predicts new effects that can not be derived from the conventional theory of Flory and Stockmayer, and an exact solution is obtained for the Bethe lattice, and is related to recent experimental results of Tanaka.
Abstract: A new model for polymer gelation is presented that predicts new effects that can not be derived from the conventional theory of Flory and Stockmayer. An exact solution is obtained for the Bethe lattice, and is related to recent experimental results of Tanaka. Under certain conditions, the gelation curve terminates at the consolute point; at this point, both connectivity and concentration fluctuations are critical, just as in the random magnet at the percolation threshold.
262 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...Later, Coniglio et al. (1979, 1982) modified the model to account for the presence of solvent molecules....
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TL;DR: The erosion rate of genetically engineered protein hydrogels can be tuned by harnessing selective molecular recognition, discrete aggregation number and orientational discrimination of coiled-coil protein domains.
Abstract: Erosion behaviour governs the use of physical hydrogels in biomedical applications ranging from controlled release to cell encapsulation. Genetically engineered protein hydrogels offer unique means of controlling the erosion rate by engineering their amino acid sequences and network topology. Here, we show that the erosion rate of such materials can be tuned by harnessing selective molecular recognition, discrete aggregation number and orientational discrimination of coiled-coil protein domains. Hydrogels formed from a triblock artificial protein bearing dissimilar helical coiled-coil end domains (P and A) erode more than one hundredfold slower than hydrogels formed from those bearing the same end domains (either P or A). The reduced erosion rate is a consequence of the fact that looped chains are suppressed because P and A tend not to associate with each other. Thus, the erosion rate can be tuned over several orders of magnitude in artificial protein hydrogels, opening the door to diverse biomedical applications.
262 citations
"Interplay Between Long-Range And Sh..." refers background in this paper
...This reversible property makes physical gel an ideal candidate for drug delivery or intelligent materials responsive to physical stimuli such as pH, temperature, or radiation (Petka et al., 1998; Shen et al., 2006)....
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TL;DR: A surface forces apparatus was used to directly measure the force-distance interaction between a polymer-tethered ligand and its receptor and its dynamics can be modeled with standard theories of polymer and colloidal interactions.
Abstract: Many biological recognition interactions involve ligands and receptors that are tethered rather than rigidly bound on a cell surface. A surface forces apparatus was used to directly measure the force-distance interaction between a polymer-tethered ligand and its receptor. At separations near the fully extended tether length, the ligands rapidly lock onto their binding sites, pulling the ligand and receptor together. The measured interaction potential and its dynamics can be modeled with standard theories of polymer and colloidal interactions.
250 citations
"Interplay Between Long-Range And Sh..." refers background or methods in this paper
...Let’s take the surface force measurement (Wong et al., 1997; Jeppesen et al., 2001) as an example....
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...This model is widely used in bioengineering applications (Garcia, 2006) and biophysical measurements (Wong et al., 1997; Jeppesen et al., 2001)....
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...Polymer-tethering has also been a common motif in surface force measurements and single-molecule studies (Wong et al., 1997; Jeppesen et al., 2001)....
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TL;DR: An interferometric technique for the local measurement of bending modulus, membrane tension, and adhesion energy of motile cells adhering to a substrate was employed to quantify changes caused by the lack of talin or cortexillin I or II.
242 citations