Electrodiffusion active pump model with asymmetric immersed chemical potentials

Area of Science:

• Biophysics
• Computational Biology
• Electrophysiology

Background:

• Active pumps are vital for cellular homeostasis and maintaining physiological states.
• Understanding electrodiffusion is key to electrophysiology and cellular processes like division and apoptosis.
• Existing models often assume electroneutrality, which may not hold true in thin membrane layers.

Purpose of the Study:

• To develop a computational model for active pumps that resolves thin space charge layers without assuming electroneutrality.
• To investigate the role of active pumps in cellular volume homeostasis and ionic transport.
• To provide a foundation for applying electrodiffusion models to subcellular transport.

Main Methods:

• Utilized the immersed boundary (IB) method, replacing classical interface conditions with regularized chemical potentials.
• Governed ion permeation using the Poisson-Nernst-Planck equation.
• Incorporated energetic gradients via smoothed Heaviside kernels to represent active pump directions.

Main Results:

• The model successfully simulates electroneutrality, except for thin space charge layers.
• Demonstrated that active pumps are necessary for volume conservation in steady states.
• Showed that van't Hoff's law is satisfied when active pumps are absent.

Conclusions:

• The developed IB electrodiffusion active pump model accurately captures cellular volume regulation.
• The model framework is applicable to various physiological and disease states involving coupled electrical and osmotic effects.
• This work lays the groundwork for modeling subcellular transport, cell motility, and migration.