Charge regulation radically modifies electrostatics in membrane stacks

TL;DR

This study investigates how charge regulation through (de)protonation affects electrostatic interactions in membrane stacks, revealing complex charge patterns that depend on environmental conditions, with implications for biological membrane organization.

Contribution

It introduces a model showing that charge regulation causes symmetry-breaking and quasiperiodic charge patterns in membrane stacks, a novel insight into membrane electrostatics.

Findings

Charge regulation leads to symmetry-broken charge states.

Complex, inhomogeneous charge equilibria depend on multiple parameters.

Results provide insights into the organization of thylakoid membrane stacks.

Abstract

Motivated by biological membrane-containing organelles in plants and photosynthetic bacteria, we study charge regulation in a model membrane stack. Considering (de)protonation as the simplest mechanism of charge equilibration between the membranes and with the bathing environment, we uncover a symmetry-broken charge state in the stack with a quasiperiodic effective charge sequence. In the case of a monovalent bathing salt solution our model predicts complex, inhomogeneous charge equilibria depending on the strength of the (de)protonation reaction, salt concentration, intermembrane separation, and their number in the stack. Our results shed light on the basic reorganization mechanism of thylakoid membrane stacks.