Charge regulation radically modifies electrostatics in 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 symmetrybroken 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. * majee@is.mpg.de arXiv:1909.00217v2 [cond-mat.soft]

Charge regulation of a surface immersed in an electrolyte solution

“…Indeed, this has been suggested before for the counterion-only case [48]. Note also that charge regulation may lead to phase transitions in other charged systems as well [33][34][35].…”

“…where x p ≡ κ(z + z p ), κz p ≡ − log γ p , and γ p are given by eqs. (35) and (36) for p = 1 and p = 2, respectively. Using eq.…”

“…Therefore, the derivative of the electrostatic potential at the surface is related to a renormalized surface charge density, which leads to a non-linear charge regulation boundary condition. The NP charge regulation model has been extensively studied to address different phenomena [28,29,[33][34][35], and in particular, it may give a viable interpretation for the discrepancy between the pressure (between similarly charged surfaces) predicted by the PB theory and that measured by atomic force microscopy experiments [21,23,24]. For example, Montes et al [21] have measured the force between two charged surfaces across aqueous salt solutions containing ions of various valences, and their data show the necessity for charge regulation, especially for systems containing higher valence counterions, suggesting that Coulomb interaction may be one of physical mechanisms for charge regulation.…”

Membrane Adhesion via Glycolipids Occurs for Abundant Saccharide Chemistries

“…where r 0 is the number density of monovalent ions according to their bulk concentration of c 0 ¼ 100 mM, e is the electron charge, and j m is the electric potential at the midplane (i.e., the center of the water layer), which depends on the charge density of the surfaces (see Supporting Materials and Methods) and is thus determined by f neg . Note that the strength of the repulsion may be affected in general by charge regulation when the charged groups are protonatable (37). The repulsion associated with the incorporation of negatively charged lipids is seen most prominently for interacting PC membranes without glycolipids (f gly ¼ 0; see Fig.…”

Role of Protein-Water Interface in the Stacking Interactions of Granum Thylakoid Membranes—As Revealed by the Effects of Hofmeister Salts

“…It is shown that variations in the electrostatic forces, which might be modulated by ionic movements (see above) or by the phosphorylation of LHCII or other phosphoproteins, affect both the lateral organization and stability of stacking. Other theoretical calculations have also shown that charge movements exert very strong effect on stacking interaction of membranes, and thus on the structural dynamics of grana ( Majee et al, 2019 ). Within the frameworks of a theoretical model, investigating the effect of Mg 2+ on the entropy of the system, it has been proposed that the underlying physical mechanisms might be a combination of several events: i) the attraction between discrete, oppositely-charged areas of grana; ii) the release of loosely-bound water molecules from the interthylakoidal space; iii) variations in the orientational freedom of water dipoles; and iv) the lateral rearrangements of membrane components ( Jia et al, 2014 ).…”