Semiflexible Polymers near Attracting Surfaces

Кузнецов, Д. В.; Sung, Wonyong

doi:10.1021/ma970827m

Cited by 24 publications

(29 citation statements)

References 22 publications

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“…This is in accord with previous calculations [161,162,163,164,165] and simulations [166] for a semi-flexible polymer bound by short-ranged (square-well) potentials. Setting D ∼ κ −1 in Eq.…”

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confidence: 92%

Neutral and charged polymers at interfaces

2003

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Chain-like macromolecules (polymers) show characteristic adsorption properties due to their flexibility and internal degrees of freedom, when attracted to surfaces and interfaces. In this review we discuss concepts and features that are relevant to the adsorption of neutral and charged polymers at equilibrium, including the type of polymer/surface interaction, the solvent quality, the characteristics of the surface, and the polymer structure. We pay special attention to the case of charged polymers (polyelectrolytes) that have a special importance due to their water solubility. We present a summary of recent progress in this rapidly evolving field. Because many experimental studies are performed with rather stiff biopolymers, we discuss in detail the case of semi-flexible polymers in addition to flexible ones. We first review the behavior of neutral and charged chains in solution. Then, the adsorption of a single polymer chain is considered. Next, the adsorption and depletion processes in the many-chain case are reviewed. Profiles, changes in the surface tension and polymer surface excess are presented. Mean-field and corrections due to fluctuations and lateral correlations are discussed. The force of interaction between two adsorbed layers, which is important in understanding colloidal stability, is characterized. The behavior of grafted polymers is also reviewed, both for neutral and charged polymer brushes.

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confidence: 92%

Neutral and charged polymers at interfaces

2003

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“…Polymer adsorption can dramatically affect the chain geometry and statistics, as demonstrated in a number of works [40,41,42,43,44,45,46]. However, the effect of nonequilibrium adsorption of semiflexible polymers is still not well understood.…”

Section: E Out-of-equilibrium Adsorption Modelmentioning

confidence: 99%

High flexibility of DNA on short length scales probed by atomic force microscopy

et al. 2006

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Because of thermal fluctuations, a polymer chain at room temperature will be bent. WLC and our model both predict that the molecule's observed conformations will be drawn from a certain probability distribution of shapes, obtained by combining bends distributed according to Boltzmann statistics with some energy function E(θ). Our task is to evaluate E(θ) from data.A comprehensive theory of DNA bending on short length scales must also include the twist degrees of freedom [1], as well as inhomogeneities from sequence [2,3]. Indeed, recent cyclization experiments suggest that the harmonic-elasticity model for the twist response of DNA also overstates the energetic cost of twist when curvature is high [4]. Thus, it seems likely that the twist energy function must be modified in a manner analogous to the one we have proposed for the bending energy. We leave this generalization to future work. For the random sequences studied here, we expect bending anisotropy to be a small effect for behavior on length scales greater than the helical pitch of 3.5 nm. Sequence dependent curvature, in natural DNA and in modified constructs with nonstandard bases, has been observed in AFM studies [5,6]; again we leave the extension of our model to include sequence to future work. A.2 Scale dependence in equilibrium statistical physicsHere we briefly elaborate on some ideas of scale dependence in equilibrium statistical physics, applied to our problem.The conformation of a macromolecule like DNA can usefully be described on any of several length scales. That is, when describing the molecule's behavior on a length scale ℓ exp larger than the size of individual atoms, we can often simplify our description by imagining the macromolecule to be composed

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“…The perturbative solution of Eq. (2) in the absence of the βl p γf term, due to Kuznetsov and Sung [27], to the first order in correlation length parameter η=(4l 2 p /ψ 0 )|d 2 ψ 0 /dx 2 | is outlined in Appendix A. The solution is…”

Section: Theorymentioning

confidence: 99%

Influence of Surface Interactions on Folding and Forced Unbinding of Semiflexible Chains

Barsegov

Thirumalai

2005

J. Phys. Chem. B

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We have investigated the folding and forced unbinding transitions of adsorbed semiflexible polymer chains using theory and simulations. These processes describe, at an elementary level, a number of biologically relevant phenomena that include adhesive interactions between proteins and tethering of receptors to cell walls. The binding interface is modeled as a solid surface, and the wormlike chain (WLC) is used for the semiflexible chain (SC). Using Langevin simulations, in the overdamped limit we examine the ordering kinetics of racquet-like and toroidal structures in the presence of an attractive interaction between the surface and the polymer chain. For a range of interactions, temperature, and the persistence length, l(p), we obtained the monomer density distribution, n(x), (x is the perpendicular distance of a tagged chain end from the surface) for all of the relevant morphologies. There is a single peak in n(x) inside the range of attractive forces, b, for chains in the extended conformations, whereas in racquet and toroidal structures there is an additional peak at x approximately b. The simulated results for n(x) are in good agreement with theory. The formation of toroids on the surface appears to be a first-order transition as evidenced by the bimodal distribution in n(x). The theoretical result underestimates the simulated n(x) for x << b and follows n(x) closely for x >/= b; the calculated density agrees exactly with n(x) in the range x << b. The chain-surface interaction is probed by subjecting the surface structures to a pulling force, f. The average extension, x( f), as a function of f exhibits a sigmoidal profile with sharp all-or-none transition at the unfolding force threshold f = f(c) which increases for more structured states. Simulated x(f) compare well with the theoretical predictions. The critical force, f(c), is a function of l(s)/l(c) for a fixed temperature, where l(c) and l(s) are the length scales that express the strength of the intramolecular and SC-surface attraction, respectively. For a fixed l(s), f(c) increases as l(p) decreases.

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Semiflexible Polymers near Attracting Surfaces

Cited by 24 publications

References 22 publications

Neutral and charged polymers at interfaces

Neutral and charged polymers at interfaces

High flexibility of DNA on short length scales probed by atomic force microscopy

Influence of Surface Interactions on Folding and Forced Unbinding of Semiflexible Chains

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