Confined semiflexible polymers suppress fluctuations of soft membrane tubes

Abstract

We use Monte Carlo computer simulations to investigate tubular membrane structures with and without semiflexible polymers confined inside. At small values of membrane bending rigidity, empty fluid and non-fluid membrane tubes exhibit markedly different behavior, with fluid membranes adopting irregular, highly fluctuating shapes and non-fluid membranes maintaining extended tube-like structures. Fluid membranes, unlike non-fluid membranes, exhibit a local maximum in specific heat as their bending rigidity increases. The peak is coincident with a transition to extended tube-like structures. We further find that confining a semiflexible polymer within a fluid membrane tube reduces the specific heat of the membrane, which is a consequence of suppressed membrane shape fluctuations. Polymers with a sufficiently large persistence length can significantly deform the membrane tube, with long polymers leading to localized bulges in the membrane that accommodate regions in which the polymer forms loops. Analytical calculations of the energies of idealized polymer-membrane configurations provide additional insight into the formation of polymer-induced membrane deformations.

Membrane-mediated interactions between hinge-like particles

“…The details are presented in previous work. 33,38 For nanoparticles, we use a pivot move, 39,40 where one rod of nanoparticles is randomly selected and rotated by a random angle around the axis through the hinge bead with random orientation. All trial moves are accepted or rejected according to the standard Metropolis criterion, and the We first equilibrate the system for 1 × 10 6 MCS with nanoparticles and the membrane well separated so that they equilibrate independently.…”

Equilibrium morphologies of a macromolecule under soft confinement

“…Similar theories have been applied to macromolecules in soft tubular confinement and a phase diagram characterising confined polymer shapes as a function of the surface tension and the size of the chain obtained [4]. Electrophoresis experiments on DNA confined in nanometer sized lipid tubules [9] reveal a “snake” to “globule” conformational transition [4] while Monte Carlo [22, 23] and molecular dynamics [24] simulations have been used to confirm the scaling behavior. These studies however, do not fully capture the effects of semiflexibility and the nonlinear mechanics of the confining tubule on the conformational properties of the macromolecule which sets the stage of the current work.…”

Theoretical Platform for Liquid-Crystalline Self-Assembly of Collagen-Based Biomaterials

“…Simplicity of free energy expression is essential since our ultimate objective is the self-assembly simulation which in itself is computationally complex. A heavy computational load is expected because the self-assembly process covers a wide range of length scale (i.e., ranging from nano-to macro-scale) and it may go through a variety of complex microscopic mechanisms [41,[55][56][57][58][59]. Thus, to improve tractability, we expand the functional part of Equation (15), Ŵ (γ), in terms of the second Legendre polynomial by use of Equation 8:…”