Fractal and statistical properties of large compact polymers: A computational study

Rhonald Lua, Alexander L. Borovinskiy, Alexander Yu Grosberg

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We propose a novel combinatorial algorithm for efficient generation of Hamiltonian walks and cycles on a cubic lattice, modeling the conformations of lattice toy proteins. Through extensive tests on small lattices (allowing complete enumeration of Hamiltonian paths), we establish that the new algorithm, although not perfect, is a significant improvement over the earlier approach by Ramakrishnan et al. [J Chem Phys 103(17) 7592 (1995)], as it generates the sample of conformations with dramatically reduced statistical bias. Using this method, we examine the fractal properties of typical compact conformations. In accordance with Flory theorem celebrated in polymer physics, chain pieces are found to follow Gaussian statistics on the scale smaller than the globule size. Cross-over to this Gaussian regime is found to happen at the scales which are numerically somewhat larger than previously believed. We further used Alexander and Vassiliev degrees 2 and 3 topological invariants to identify the trivial knots among the Hamiltonian loops. We found that the probability of being knotted increases with loop length much faster than it was previously thought, and that chain pieces are consistently more compact than Gaussian if the global loop topology is that of a trivial knot.

    Original languageEnglish (US)
    Pages (from-to)717-731
    Number of pages15
    JournalPolymer
    Volume45
    Issue number2
    DOIs
    StatePublished - Jan 15 2004

    Keywords

    • Compact Hamiltonian walks on a lattice
    • Knots
    • Polymer statistics

    ASJC Scopus subject areas

    • Organic Chemistry
    • Polymers and Plastics
    • Materials Chemistry

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