title: Elasticity of flexible and semiflexible polymers with extensible bonds in the Gibbs and Helmholtz ensembles.
abstract: Stretching experiments on single molecules of arbitrary length opened the way for studying the statistical mechanics of small systems. In many cases in which the thermodynamic limit is not satisfied, different macroscopic boundary conditions, corresponding to different statistical mechanics ensembles, yield different force-displacement curves. We formulate analytical expressions and develop Monte Carlo simulations to quantitatively evaluate the difference between the Helmholtz and the Gibbs ensembles for a wide range of polymer models of biological relevance. We consider generalizations of the freely jointed chain and of the worm-like chain models with extensible bonds. In all cases we show that the convergence to the thermodynamic limit upon increasing contour length is described by a suitable power law and a specific scaling exponent, characteristic of each model.
authors.affiliation: Dipartimento di Fisica, Università di Cagliari, Cittadella Universitaria, 09042 Monserrato, Cagliari, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Manca
authors.forename: Stefano
authors.initials: S
authors.lastname: Giordano
authors.forename: Pier Luca
authors.initials: PL
authors.lastname: Palla
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Zucca
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Cleri
authors.forename: Luciano
authors.initials: L
authors.lastname: Colombo
mesh_terms: D004548:Elasticity; D009010:Monte Carlo Method; D011108:Polymers / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D011108:Polymers