Stretching and compression of a macromolecule under different modes of mechanical manupulations

Skvortsov, A.M.; Klushin, Leonid I.; Birshtein, T.M.

doi:10.1134/s0965545x09050010

Cited by 23 publications

(71 citation statements)

References 54 publications

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“…The excluded volume and finite extensibility effects in real macromolecules lead to a non Gaussian distribu tion function and to deviations from linear elasticity. The full equivalence of ensembles for non Gaussian chains of finite length is violated, as was shown in [5,6].…”

Section: Gaussian Chainmentioning

confidence: 97%

“…(An elongated stem and a coil like cap in a chain squeezed out of the piston can be regarded as two microphases.) Examples of nonpolymer systems with a similar anomalous behavior were given in recent review [5].…”

Section: Introductionmentioning

confidence: 95%

“…The scalar distance can significantly differ from the z coordinate, a result unlike that of an AFM experi ment, in which they coincide. The equilibrium aver age scalar distance is calculated as follows: (5) where is the angle between vectors f and r and is the end to end distance distribution function in an arbitrary fixed direction, in particular, = .…”

Section: Stretching Via Magnetic Levitationmentioning

confidence: 99%

“…The discussion of this issue is one of the sub jects of this study. Note that, although our review has something in common with [5], it contains some new sections: (i) We discuss the mechanical effects corre sponding to the methods of atomic force microscopy (AFM) and the stretching of a macromolecule in an isotropic force field, not only the case of stretching implemented in the magnetic levitation method con sidered in [5]; (ii) we analyze the data of computer simulations of the stretching of a Gaussian polymer chain in the different ensembles, which implies that the statement of the authors of [7] on the nonequiva lence of conjugated ensembles for Gaussian chains is incorrect; and (iii) we present rigorous analytical results on the stretching of semirigid chains composed of two or three freely jointed rigid rods of equal length and show that the stress-strain curves of these chains in the different ensembles have not only quantitative differences but also qualitative differences.…”

Section: Introductionmentioning

confidence: 99%

“…To clarify the physical nature of the variety of opinions, we have deliberately restricted ourselves to the examination of simple models of homopolymers in a good solvent and a solvent, while avoiding a detailed discussion of experimental data and focusing on the analysis of the ories and computer simulation results. Note that the problem of equivalence and nonequivalence of ensembles in more complex situations (the separation of adsorbed molecules from a solid substrate, the mechanical collapse of a polymer globule, and the deformation of a chain squeezed between pistons) has been discussed in recent review [5]. Note that, in θ experimental AFM studies of the stretching of individ ual molecules, one end of a macromolecule is usually grafted or rigidly anchored to the surface of a solid substrate via chemisorption, while the other end is fixed on the surface of a micron sized probe.…”

Section: Introductionmentioning

confidence: 99%

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How to understand the ensemble equivalence during stretching of a single macromolecule

2012

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In this paper, we discuss the elastic behavior of an isolated macromolecule in conjugated and non conjugated ensembles during different modes of applying a mechanical force to the chain ends, namely, the mechanical effects corresponding to the methods of atomic force microscopy, magnetic levitation, and stretching of a macromolecule in an isotropic force field. Recently published results on the Langevin dynam ics computer simulation of the stretching of a Gaussian polymer chain in different ensembles are analyzed. An analytical description of all the results of this simulation is given to show that the conclusion made by the authors of those studies about the nonequivalence of conjugated ensembles for Gaussian chains is not quite correct. A theoretical examination of the stretching of individual semirigid chains, which exhibit interesting behavior because of manipulations with actin molecules and microtubules, which are components of the cytoskeleton of most cells, is performed. We present rigorous analytical results about the stretching of chains composed of two or three freely jointed rods of equal length without consideration for excluded volume inter actions. It is shown that the stress-strain curves of these chains differ not only quantitatively but also quali tatively in different ensembles and that these curves for a chain of two freely jointed rods have an anomalous shape. These results on the different behavior of stress-strain for different modes of external mechanical impacts can be useful for interpreting experiments on the stretching of individual polymer molecules with dif ferent structures obtained via different methods, such as atomic force microscopy and magnetic levitation.

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Section: Gaussian Chainmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 95%

Section: Stretching Via Magnetic Levitationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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How to understand the ensemble equivalence during stretching of a single macromolecule

2012

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Mechanical Unfolding of a Homopolymer Globule: Applied Force versus Applied Deformation

Polotsky

Smolyakova

Borisov

et al. 2010

Macromolecular Symposia

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Summary:We propose the quantitative mean-field theory of mechanical unfolding of a globule formed by long flexible homopolymer chain collapsed in poor solvent and subjected to an extensional force We show that with an increase in the applied force the globule unfolds as a whole without formation of an intermediate state. The value of the threshold force and the corresponding jump in the distance between chain ends increase with a deterioration of the solvent quality and / or with an increase in the degree of polymerization. This way of globule unfolding is compared with that in the D-ensemble, when the distance between chain ends is imposed.

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Stretching of Anchored to the Surface a Real Polymer Chain in a Good Solvent: The Massive Field Theory Approach

Usatenko

2014

Macromolecular Symposia

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Summary Application of the massive field theory approach in a fixed space dimensions d = 3 up to one loop order for investigation of the elastic properties of a real polymer chain immersed in a good solvent and anchored by one end to the surface and with other end being under tension of the external applied force as it is usually takes place in the single ‐ molecule force spectroscopy experiments. The obtained results include calculations of the dependence of the applied force upon stretching of a real polymer chain in a good solvent on the distance from the repulsive and inert surfaces. Besides, the obtained results are in good qualitative and quantitative agreement with previous theoretical investigations, results of Density Functional Theory (DFT) and Monte Carlo (MC) simulations and have important practical applications for understanding of the elastic properties of the individual macromolecules, networks, gels and brush layers.

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Stretching and compression of a macromolecule under different modes of mechanical manupulations

Cited by 23 publications

References 54 publications

How to understand the ensemble equivalence during stretching of a single macromolecule

How to understand the ensemble equivalence during stretching of a single macromolecule

Mechanical Unfolding of a Homopolymer Globule: Applied Force versus Applied Deformation

Stretching of Anchored to the Surface a Real Polymer Chain in a Good Solvent: The Massive Field Theory Approach

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