Simulation of short-chain polymer collapse with an ...



Title Simulation of short-chain polymer collapse with an explicit solvent
Author(s) James M. Polson, M. J. Zuckermann
Journal Journal of Chemical Physics
Date 2002
Volume 116
Issue 16
Start page 7244
End page 7254
Abstract We study the equilibrium behavior and dynamics of a polymer collapse transition for a system composed of a short Lennard-Jones (LJ) chain immersed in a LJ solvent for solvent densities in the range of rho=0.6-0.9 (in LJ reduced units). The monomer hydrophobicity is quantified by a parameter lambdais an element of[0,1] which gives a measure of the strength of attraction between the monomers and solvent particles, and which is given by lambda=0 for a purely repulsive interaction and lambda=1 for a standard LJ interaction. A transition from the Flory coil to a molten globule is induced by increasing lambda. Generally, the polymer size decreases with increasing solvent density for all lambda. Polymer collapse is induced by changing the hydrophobicity parameter from lambda=0 to lambdagreater than or equal to0.5, where the polymer is in a molten globule state. The collapse rate increases monotonically with increasing hydrophobicity and decreases monotonically with increasing solvent density. Doubling the length of the chain from N=20 to N=40 monomers increases the collapse time roughly by a factor of 2, more or less independent of the hydrophobicity and solvent density. We also study the effect of conformational restrictions on polymer collapse using a chain model in which the bond angles are held near 109.5degrees using a stiff angular harmonic potential, but where free internal rotation is allowed, and find that the collapse times increase considerably with respect to the fully flexible polymer, roughly by a factor of 1.6-3.5. This increase is most pronounced for high solvent densities. (C) 2002 American Institute of Physics.
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