All-or-none protein-like folding of a homopolymer chain

ORAL

Abstract

Many small proteins fold via a first-order ``all-or-none'' transition directly from an expanded coil to a compact native state. Here we report an analogous direct freezing transition from an expanded coil to a compact crystallite for a simple flexible homopolymer. Wang-Landau sampling is used to construct the complete density of states for square-well chains up to length 256. Analysis within both the microcanonical and canonical ensembles shows that, for a chain with sufficiently short-range interactions, the usual polymer collapse transition is preempted by a direct freezing transition. Despite the non-unique homopolymer ground state, the thermodynamics of this direct freezing transition are identical to the thermodynamics of two-state protein folding. A free energy barrier separates a high entropy ensemble of unfolded states from a low entropy set of crystallite states and the transition proceeds via the formation of a transition-state folding nucleus. An Arrhenius analysis of the folding/unfolding free energy barrier yields a Chevron plot characteristic of proteins and the model chain satisfies the van't Hoff calorimetric criterion for two-state folding.

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Authors

  • Mark Taylor

    Hiram College, Dept. of Physics, Hiram College

  • Kurt Wiesenfeld

    Miami University, Summa Health System, Akron, John Carroll University, Prof, Dr, BfS, Germany, Florida State University, Monmouth College, Ohio Wesleyan University, Kenyon College, University of Cincinnati, Brookhaven National Lab, University of Wisconsin Oshkosh, Dept. of Chermical Engineering, Carnegie Mellon University, Cleveland State University, The Neurological Institute, Epilepsy Center, Department of Neurology, Cleveland Clinic, Un. of Stockholm, The University of Akron, Case Western Reserve University, West Virginia University, Kalamazoo College and Editor, American Journal of Physics, Denison University, University of Southern Florida, Johannes-Gutenberg-Universitat, BfS (Germany), Shanghai Jiao Tong University, Department of Physics, West Virginia University, Kansas State University, The Pennsylvania State University, University of Wisconsin-Oshkosh, Purdue University, Saint Jospeh's College, University of Washington, Indiana University, University of Potsdam, Georgia Institute of Technology

  • Kurt Wiesenfeld

    Miami University, Summa Health System, Akron, John Carroll University, Prof, Dr, BfS, Germany, Florida State University, Monmouth College, Ohio Wesleyan University, Kenyon College, University of Cincinnati, Brookhaven National Lab, University of Wisconsin Oshkosh, Dept. of Chermical Engineering, Carnegie Mellon University, Cleveland State University, The Neurological Institute, Epilepsy Center, Department of Neurology, Cleveland Clinic, Un. of Stockholm, The University of Akron, Case Western Reserve University, West Virginia University, Kalamazoo College and Editor, American Journal of Physics, Denison University, University of Southern Florida, Johannes-Gutenberg-Universitat, BfS (Germany), Shanghai Jiao Tong University, Department of Physics, West Virginia University, Kansas State University, The Pennsylvania State University, University of Wisconsin-Oshkosh, Purdue University, Saint Jospeh's College, University of Washington, Indiana University, University of Potsdam, Georgia Institute of Technology