Md Mohtasir Sheraj Qualifier Exam

Abstract: Lipid bilayer membranes are an essential component of biological cells: they are barri-

ers regulating the passage of ions and molecules, and platforms for biochemical reactions.

Lipid molecules have large dipole moments, such that external electric fields (1) affect the

energetics of lipid–lipid and lipid–water interactions and (2) cause out-of-plane membrane

shape displacements. Moreover, the dipole moment in a lipid molecule predominantly lies

parallel to the membrane surface—for which the dielectric permittivity is an anisotropic ten-

sor. In this work, we present a theory relating the microscopic fluctuations in lipid dipole

moments to the macroscopic dielectric constant, all in the context of a polarizable micro-

scopic system. We then run molecular dynamics simulations, and apply our theory to extract

the tensorial dielectric constant. Our framework addresses the limitations of existing the-

ories, which primarily describe non-polarizable systems, and can be extended to determine

electromechanical coefficients from simulations.