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Title: Wang-Landau density of states based study of the folding-unfolding transition in the mini-protein Trp-cage (TC5b)

We present the results of a high-statistics equilibrium study of the folding/unfolding transition for the 20-residue mini-protein Trp-cage (TC5b) in water. The ECEPP/3 force field is used and the interaction with water is treated by a solvent-accessible surface area method. A Wang-Landau type simulation is used to calculate the density of states and the conditional probabilities for the various values of the radius of gyration and the number of native contacts at fixed values of energy—along with a systematic check on their convergence. All thermodynamic quantities of interest are calculated from this information. The folding-unfolding transition corresponds to a peak in the temperature dependence of the computed specific heat. This is corroborated further by the structural signatures of folding in the distributions for radius of gyration and the number of native contacts as a function of temperature. The potentials of mean force are also calculated for these variables, both separately and jointly. A local free energy minimum, in addition to the global minimum, is found in a temperature range substantially below the folding temperature. The free energy at this second minimum is approximately 5 k{sub B}T higher than the value at the global minimum.
Authors:
;  [1] ;  [2]
  1. School of Physical Sciences, Jawaharlal Nehru University, New Delhi - 110 067 (India)
  2. School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi - 110 067 (India)
Publication Date:
OSTI Identifier:
22308763
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY; FREE ENERGY; INTERACTIONS; PEAKS; PROBABILITY; PROTEINS; SIMULATION; SOLVENTS; SPECIFIC HEAT; STATISTICS; SURFACE AREA; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE; WATER