Affiliation:
1. Department of Energy Engineering and Physics, Amirkabir University of Technology, Tehran 14588, Iran
2. Department of Physics, Kyungpook National University, 80 Daehakro, Bukgu, Daegu 41566, Republic of Korea
Abstract
Quite often polymers exhibit different elastic behavior depending on the statistical ensemble (Gibbs vs. Helmholtz). This is an effect of strong fluctuations. In particular, two-state polymers, which locally or globally fluctuate between two classes of microstates, can exhibit strong ensemble inequivalence with negative elastic moduli (extensibility or compressibility) in the Helmholtz ensemble. Two-state polymers consisting of flexible beads and springs have been studied extensively. Recently, similar behavior was predicted in a strongly stretched wormlike chain consisting of a sequence of reversible blocks, fluctuating between two values of the bending stiffness (the so called reversible wormlike chain, rWLC). In this article, we theoretically analyse the elasticity of a grafted rod-like semiflexible filament which fluctuates between two states of bending stiffness. We consider the response to a point force at the fluctuating tip in both the Gibbs and the Helmholtz ensemble. We also calculate the entropic force exerted by the filament on a confining wall. This is done in the Helmholtz ensemble and, under certain conditions, it yields negative compressibility. We consider a two-state homopolymer and a two-block copolymer with two-state blocks. Possible physical realizations of such a system would be grafted DNA or carbon nanorods undergoing hybridization, or grafted F-actin bundles undergoing collective reversible unbinding.
Funder
Iran’s National Elites Foundation
National Research Foundation of Korea
Ministry of Science and ICT, Korea
Subject
Polymers and Plastics,General Chemistry
Reference46 articles.
1. Balian, R., Haar, D., and Gregg, J. (2006). From Microphysics to Macrophysics: Methods and Applications of Statistical Physics, Springer.
2. Classification of Phase Transitions and Ensemble Inequivalence, in Systems with Long Range Interactions;Bouchet;J. Stat. Phys.,2005
3. How to Understand the Ensemble Equivalence during Stretching of a Single Macromolecule;Ivanov;Polym. Sci. Ser. A,2012
4. Single-molecule force spectroscopy: Optical tweezers, magnetic tweezers and atomic force microscopy;Neuman;Nat. Methods,2008
5. Relating Single-Molecule Measurements to Thermodynamics;Keller;Biophys. J.,2003
Cited by
1 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献