Search results for "Biomolecule"
showing 10 items of 666 documents
Monte-Carlo Simulation of 3-Dimensional Glassy Polymer Melts: Reptation Versus Single Monomer Dynamics
1995
A polymer melt is simulated at finite temperature by the Monte-Carlo method. We use a coarse-grained model for the polymer system, the bond-fluctuation model. Static properties of the melt can be obtained by generating configurations not with single-monomer- dynamics which moves individual monomers locally, but reptation-dynamics which allows collec- tive motion of the chains. This algorithm can produce equilibrated configurations much faster. It is demonstrated that static properties do not differ from those obtained by single-monomer- dynamics. Values of the radius of gyration, the mean square bond length and similar quantities for different temperatures and densities are presented.
Biomolecular-solvent stereodynamic coupling probed by deuteration.
1983
Thermodynamic interpretation of experiments with isotopically perturbed solvent supports the view that solvent stereodynamics is directly relevant to thermodynamic stability of biomolecules. According with the current understanding of the structure of the aqueous solvent, in any stereodynamic configuration of the latter, connectivity pathways are identifiable for their topologic and order properties. Perturbing the solvent by isotopic substitution or, e.g., by addition of co-solvents, can therefore be viewed as reinforcing or otherwise perturbing these topologic structures. This microscopic model readily visualizes thermodynamic interpretation. In conclusion, the topologic stereodynamic str…
Conformational Properties of Polymer Mushrooms Under Spherical and Cylindrical Confinement
2010
A coarse grained model of a flexible macromolecule end-grafted on the inside of a sphere or a cylinder under good solvent conditions is studied by Monte Carlo simulations. For cylindrical confinement, two regimes are found: when the cylinder radius R exceeds the gyration radius R 90 of the polymer mushroom grafted to a planar surface, a simple scaling description holds. In the opposite case, a non-monotonic crossover to a cigar-like quasi-one-dimensional structure occurs, and the distribution P e (x) of the free chain end in the x-direction along the cylinder axis becomes bimodal. Spherical confinement, on the other hand, causes a crossover from dilute to semidilute behavior of the structur…
Static and Dynamic Properties of Adsorbed Chains at Surfaces: Monte Carlo Simulation of a Bead-Spring Model
1996
The adsorption of flexible polymers from dilute solution in good solvents at attractive walls is studied by Monte Carlo simulation of a coarse-grained off-lattice model, varying chain length N and ...
Brownian dynamics simulation of grafted polymer brushes
1995
We present results of computer simulations by the method of Brownian dynamics of polymeric brushes attached to impenetrable planes. For testing both model and method we have used one polymer brush attached to a repulsive plane and compare some results with Monte Carlo results of Lai and Binder on the bond fluctuation model. We have also studied two polymeric brushes attached to two parallel planes at different distances between planes, and investigate the interplay between the interpenetration of the brushes and the configurational properties of the grafted chains.
On the Reasons for an Anomalous Demixing Behavior of Polymer Solutions
2005
Some extraordinary solutions of polymers in single solvents exhibit two liquid/liquid critical points, one within the usual composition range and a second one in the range of moderate to high polymer concentration. This particularity was studied theoretically by means of a recently established approach, which accounts explicitly for chain connectivity and for the ability of polymer molecules to respond to changes in their environment by conformational rearrangements. On the basis of model calculations, it is shown that the anomalous demixing behavior, i.e., the emergence of a second critical point, is bound to the necessary but not sufficient condition that a thermodynamically very unfavora…
Ferrochirality: A simple theoretical model of interacting dynamically invertible helical polymers, 1. The basic effects
1994
The effect of interaction between reversible helical polymers of the poly(hexyl isocyanate) type is investigated by using a molecular field model. It is shown that for interacting helices a critical temperature exists below which they must adopt a common helix-sense spontaneously, even in the absence of any external or intrinsic chiral force
Structure of a bidisperse polymer brush: Monte Carlo simulation and self-consistent field results
1992
Using the bond-fluctuation model, Monte Carlo simulations are performed for polymer brushes composed of chains of two different chain lengths under good solvent condition. Profiles of monomer density and free end density, chain linear dimensions, and average monomer position along a chain are studied. Quantities measured in the simulations are derived from the analytic self-consistent field (SCF) theory and compared with the simulation data. The structural properties can be quite accurately described by the theory only when both the long and short chains are stretched
Association Equilibria Theory for Polymers in Mixed Solvents with Specific Interactions
2004
Hydrogen bonding plays an important role in determining the physical and thermodynamic properties of polar fluids. Theoretical and experimental aspects of polymers, in mixed solvents with hydrogen-bonding-specific interactions, are investigated using a simple association model based on the theory of association equilibria developed by Pouchly et al. The thermodynamic non-idealities are accounted for using a modified Flory-Huggins theory with effective g ij parameters. The entropic term of the above formalism has been formulated taking into account the pplymer segment-solvent as well as the solvent-solvent hydrogen-bond formation. Four equilibrium constants are introduced to make a realistic…
Polyelectrolytes Revisited: Reliable Determination of Intrinsic Viscosities
2007
The linear extrapolation of (hh0)/(h0c) towards c !0 constitutes the basis of traditional methods to determine intrinsic viscosities (h), where h is the viscosity of polymer solutions of concentration c and h0 is the viscosity of the pure solvent. With uncharged macromolecules this procedure works well; for polyelectrolytes it fails because of the pronounced non-linearity of the above dependence at high dilution resulting from the increasing electrostatic inter- actions. This contribution presents a new method for the determination of (h). It rests upon the application of the laws of phenomenological thermodynamics to the viscosity of polymer solutions and introduces a generalized intrinsic…