Phase state dependent current fluctuations in pure lipid membranes

TL;DR

This study investigates how current fluctuations in pure lipid membranes depend on their phase state, revealing distinct behaviors during phase transitions and proposing a theoretical model linking susceptibility and relaxation times.

Contribution

It demonstrates the phase-dependent characteristics of current fluctuations and introduces a theoretical explanation connecting membrane susceptibilities with relaxation times near phase transitions.

Findings

Current fluctuations vary with membrane phase state.

Distinct fluctuation patterns observed in fluid vs. transition states.

Proposed linear relationship between susceptibility and relaxation time.

Abstract

Current fluctuations in pure lipid membranes have been shown to occur under the influence of transmembrane electric fields (electroporation) as well as a result from structural rearrangements of the lipid bilayer during phase transition (soft perforation). We demonstrate that the ion permeability during lipid phase transition exhibits the same qualitative temperature dependence as the macroscopic heat capacity of a D15PC/DOPC vesicle suspension. Microscopic current fluctuations show distinct characteristics for each individual phase state. While current fluctuations in the fluid phase show spike-like behaviour of short time scales (~ 2ms) with a narrow amplitude distribution, the current fluctuations during lipid phase transition appear in distinct steps with time scales in the order of ~ 20ms. 1 We propose a theoretical explanation for the origin of time scales and permeability based on a linear relationship between lipid membrane susceptibilities and relaxation times in the vicinity of the phase transition.