Molecular dynamics study of the structure organization in a strongly coupled chain of charged particles

Motohiko Tanaka, A. Yu Grosberg, V. S. Pande, Toyoichi Tanaka

    Research output: Contribution to journalArticle

    Abstract

    The dynamical and equilibrium properties of a strongly coupled chain of charged particles (polyampholyte) submerged in an immobile viscous medium are studied using the molecular dynamics simulations. The polyampholyte relaxes to an equilibrium conformation typically in 300ωpe -1 due to folding of the chain for low temperatures, and expands several times faster for high temperatures, where ωpe is the plasma frequency. Three regimes with distinct conformations as stretched, oblate, and spherical are observed under the Coulomb force at high, medium, and low temperatures, respectively. The change in the conformations is considered to minimize the free energy through the electrostatic potential. The root-mean-squared size of the polyampholytes in these regimes is scaled, respectively, as Rg∼N1/2, (NT)1/3, and N0.3T0.8-1.0, where N is the number of monomers on the chain and T the temperature. The crossover point of the regimes is characterized by the unique values of the monomer distance 2Rg/N1/3, being insensitive to the length and stiffness of the chain. The present results agree well with the Flory theory in the high and medium temperature regimes. The densely packed state at low temperatures is first obtained here without the use of the lattice model. The transition among the different regimes under the Coulomb force is exactly reversible. However, the transition under the cooperation of the Coulomb force and the attractive short-range force exhibits a hysteresis against successive changes in temperature.

    Original languageEnglish (US)
    Pages (from-to)5798-5808
    Number of pages11
    JournalPhysical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics
    Volume56
    Issue number5 SUPPL. B
    StatePublished - Nov 1997

    Fingerprint

    Molecular Dynamics
    charged particles
    Conformation
    molecular dynamics
    monomers
    temperature
    plasma frequencies
    Folding
    Lattice Model
    Hysteresis
    Electrostatics
    folding
    Molecular Dynamics Simulation
    Expand
    Crossover
    Free Energy
    stiffness
    Stiffness
    crossovers
    Plasma

    ASJC Scopus subject areas

    • Physics and Astronomy(all)
    • Condensed Matter Physics
    • Statistical and Nonlinear Physics
    • Mathematical Physics

    Cite this

    Molecular dynamics study of the structure organization in a strongly coupled chain of charged particles. / Tanaka, Motohiko; Grosberg, A. Yu; Pande, V. S.; Tanaka, Toyoichi.

    In: Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, Vol. 56, No. 5 SUPPL. B, 11.1997, p. 5798-5808.

    Research output: Contribution to journalArticle

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