Biophysics and Medical Physics

Comparison of coarse-grained and all-atom “membrane-solvent” systems as models of memcapacitors under alternating electric field

I. I. Zlochevskiy, D. V. Zav'yalov

Volgograd State Technical University

Abstract: Background and Objectives: The lipid membrane is one of the most important structures of a living cell, representing a barrier with selective permeability. Many biological processes are associated with changes in the concentration of positive and negative ions inside and outsidethe cell. Inthis regard, themembrane ismore widely represented as an electric capacitor. Inmodern studies onthe effect of an alternating field on biomolecular lipids, the existence of a nonlinear capacitance-voltage dependence is also mentioned, which makes the lipid membrane a promising candidate for the role of amemcapacitor. Since the use of practicalmembranemodels is associated with their instability, themolecular dynamics method has become widespread. A similar memory effect was obtained in studies using a coarse-grained model. On all-atom systems, this effect is poorly represented in the literature. The all-atom model more fully describes the interaction of particles, so it would be relevant to compare the coarse-grained and all-atomic membrane-solvent system as models of a memcapacitor under the influence of an alternating electric field. Materials and Methods: The studied system consisted of a lipid membrane immersed in an aqueous KCl solution. Two quantitatively similar systems consisted of 512 lipid molecules, such as dipalmitoylphosphatidylcholine (1,2-Dipalmitoyl-sn-Glycero-3-Phosphocholine), two water compartments of 40 Å and 3 M salt. Two types of force fields were used in the work, a all-atom charmm36m, as well as coarse-grained force fields martni22p and a modified force field – v2.2refPOL+refION. An alternating electric field with a strength of 0.5, 1.0 and 1.5 V/nm with a frequency of 1 GHz was applied to the systems. Molecular dynamics simulations were performed using GROMACS. Results: Under the action of the field, each system has behaved as a “classical” capacitor, where oppositely charged particles have been accumulated on opposite sides of the membrane. The nature of the ion distribution is also similar for the studied systems, positive particles are able to penetrate into the membrane, located inside the hydrophilic structures, and the charge peaks of negative particles are outside the membrane. A significant difference between the all-atom and coarse-grained models is the numerical value of the accumulated charge. Based on the results obtained, we can also talk about the nonlinear dependence of the total charge value in relation to the field strength value and the existence of the hysteresis effect. Conclusion: In this regard, the presented systems can be used to study the memcapacitive properties.

Keywords: lipid membrane, molecular dynamics, all-atom model, coarse-grained model, alternating electric field, capacitor, memcapacitor.

UDC: 53.097

Received: 07.06.2025
Revised: 28.11.2025
Accepted: 10.07.2025

DOI: 10.18500/1817-3020-2025-25-4-449-459