Diffusion through complex confining environments: fluctuating triply periodic minimal surfaces

TL;DR

This paper investigates how fluctuations in complex triply periodic membrane structures influence the diffusion of particles, revealing that membrane dynamics can intermittently enable larger objects to pass through pores, affecting overall transport behavior.

Contribution

It introduces a phase field model to analyze the impact of membrane fluctuations on diffusion in triply periodic structures, highlighting the role of pore widening events in particle transport.

Findings

Membrane fluctuations can intermittently allow larger particles to pass through pores.

The mean squared displacement shows a plateau indicating trapping and release dynamics.

The scenario is applicable to protein diffusion in biological environments.

Abstract

The transport of individual entities through interconnected structures is a process of practical relevance both in biology and technology. Examples are given by diffusive dynamics of molecules in porous structures. In soft environments, this transport can be strongly influenced by fluctuations of the porous structure itself. Here, we focus on triply periodic membrane structures found both in cell organelles and in synthetic amphiphilic systems. We theoretically study the effect of a complex three-dimensional fluctuating environment on the diffusive motion of a test object, using a phase field approach. The rigid spherical test object is energetically forced to not penetrate the membrane. Generally, the pores of the membrane structure can be smaller than the diffusing object. Yet, fluctuations of the membrane can intermittently widen its pores, still allowing for the motion of the larger particles through them. Thus, the object stays trapped for a while inside one cavity formed by the membrane, before an appropriate fluctuation event widens a membrane pore in the right moment so that the object can jump into the next cavity. The process is reflected by a pronounced plateau in the time evolution of the mean squared displacement. We think that the described scenario should be directly observable, for instance, in protein diffusion through biological environments.