Contribution of dipolar bridging to phospholipid membrane interactions: A mean-field analysis

Abstract

We develop a model of interacting zwitterionic membranes with rotating surface dipoles immersed in a monovalent salt and implement it in a field theoretic formalism. In the mean-field regime of monovalent salt, the electrostatic forces between the membranes are characterized by a non-uniform trend: at large membrane separations, the interfacial dipoles on the opposing sides behave as like-charge cations and give rise to repulsive membrane interactions; at short membrane separations, the anionic field induced by the dipolar phosphate groups sets the behavior in the intermembrane region. The attraction of the cationic nitrogens in the dipolar lipid headgroups leads to the adhesion of the membrane surfaces via dipolar bridging. The underlying competition between the opposing field components of the individual dipolar charges leads to the non-uniform salt ion affinity of the zwitterionic membrane with respect to the separation distance; large inter-membrane separations imply anionic excess, while small nanometer-sized separations favor cationic excess. This complex ionic selectivity of zwitterionic membranes may have relevant repercussions on nanofiltration and nanofluidic transport techniques.

Dielectric Manipulation of Polymer Translocation Dynamics in Engineered Membrane Nanopores

“…Furthermore, as our membrane model does not account for the molecular details of the engineered membranes, the alteration of the membrane permittivity was taken into account by a uniform membrane permittivity coefficient. The net effect of the corresponding approximations can be evaluated in future works via the explicit inclusion of the ionic and solvent charge structure, 67 the dipolar membrane structure, 68 and surface adsorption effects specific to the corresponding membrane material.…”

Systematic Incorporation of Ionic Hard-Core Size into the Debye–Hückel Theory via the Cumulant Expansion of the Schwinger–Dyson Equations

“…In the context of conventional statistical mechanics, the field theory approach to electrostatic interactions has emerged as an efficient and convenient alternative to the aforementioned calculation techniques. − Owing to its formulation as an explicit partition function, the technical advantages provided by the field theory framework are numerous. First of all, this approach allows the treatment of many-body interactions via systematic and controlled perturbation techniques − as well as self-consistent computation schemes. − Then, the field theory formalism enables the straightforward incorporation of the specific molecular details of electrolytes beyond the primitive model, such as structured solute charges, , explicit solvent molecules, , structured membranes, and polyelectrolytes with conformational degrees of freedom. − …”

“…First of all, this approach allows the treatment of many-body interactions via systematic and controlled perturbation techniques 38−41 as well as self-consistent computation schemes. 42−45 Then, the field theory formalism enables the straightforward incorporation of the specific molecular details of electrolytes beyond the primitive model, such as structured solute charges, 46,47 explicit solvent molecules, 48,49 structured membranes, 50 and polyelectrolytes with conformational degrees of freedom. 51−54 Due to the onset of competition between the electrostatic and HC interactions at submolar salt concentrations, 13 the validity of the field-theoretic models neglecting the pairwise HC interactions is limited to dilute salt solutions.…”

Schwinger-Dyson equations for composite electrolytes governed by mixed electrostatic couplings strengths

“…First of all, this approach allows the treatment of many-body interactions via systematic and controlled perturbation techniques [36][37][38][39] as well as self-consistent computation schemes [40][41][42]. Then, the field theory formalism enables the straightforward incorporation of the specific molecular details of electrolytes beyond the primitive model, such as structured solute charges [43,44], explicit solvent molecules [45,46], structured membranes [47], and polyelectrolytes with conformational degrees of freedom [48,49].…”