Confinement effects upon the separation of structural transitions in linear systems with restricted bond fluctuation ranges

Abstract

By means of advanced parallel replica-exchange Monte Carlo methods we examine the influence of elasticity and confinement on the structural transitions of linear systems with restricted bonded interaction. For this purpose, we adopt a model for coarse-grained flexible polymers of finite length in the dilute regime. Hyperphase diagrams are constructed using energy-dependent canonical quantities to demonstrate the effects of the changes in the range of the confined interaction on the liquid and solid structural phases. With increasing bonded interaction range we observe the disappearance of the liquid phase and the fusion of the gas-liquid (or Θ) and the liquid-solid transitions. One of the most remarkable features, the liquid-gas transition, changes from second to first order if the confined interaction range exceeds a threshold that separates polymeric from nonpolymeric systems. The notoriously difficult sampling of the entropically suppressed conformations in the region of very strong first-order transitions is improved by using multiple Gaussian modified ensembles.

Dilute Semiflexible Polymers with Attraction: Collapse, Folding and Aggregation

“…Interestingly, already, the variation of the short-range attraction range [101,102,103] may alter the structural transition of a flexible polymer to directly fold into its frozen state or even foster new low-temperature states. Similarly, a modification of the bond-interaction range alters the second-order collapse transition into a first-order condensation transition of coupled monomers [104]. Extending the model by torsional angles and adjusting a proper combination of confined bending and torsional angles again leads to the stabilization of helical structures [105,106].…”

Influence of bonded interactions on structural phases of flexible polymers

“…It could be shown that the stability and existence of a globular or liquid phase in models of flexible polymers depends on the effective interaction range between nonbonded monomers [7][8][9][10]. A recent study of the influence of bond confinement upon structural phases and transition behavior of a flexible chain showed that the liquid phase also disappears with increasing bond fluctuation range and the gas-liquid and the liquid-solid transition lines merge [11]. Bending restraints in helical polymers can lead to the formation of stable helix bundles, resembling tertiary structures in biopolymers [12].…”

Subphase transitions in first-order aggregation processes

“…Among the most efficient simulation methods are the generalized-ensemble Monte Carlo algorithms, such as simulated tempering [4,5], replica-exchange parallel tempering [6][7][8][9], multiple Gaussian modified ensemble (MGME) [10], together with multicanonical [11][12][13][14][15][16] and Wang-Landau sampling [17][18][19]. These have been applied successfully in numerous studies of structural phases and transition properties [20][21][22][23][24][25][26][27][28][29][30][31], surface adsorption [32][33][34][35][36][37][38][39][40][41], and aggregation [42][43][44][45][46][47] of generic off-lattice homopolymers and heteropolymers. The folding properties of coarse-grained protein models have also been examined extensively [48][49]…”