Enhanced dynamics in the anomalous melting regime of DMPG lipid membranes.

Elizabeth G Kelley,Lionel Porcar,Bela Farago,Michihiro Nagao,Paul D Butler

doi:10.1063/4.0000031

Abstract

Like many soft materials, lipids undergo a melting transition associated with a significant increase in their dynamics. At temperatures below the main melting transition (Tm), all molecular and collective dynamics are suppressed, while above Tm the alkyl tail motions, lipid diffusivity, and collective membrane undulations are at least an order of magnitude faster. Here we study the collective dynamics of dimyristoylphosphatidylglycerol (DMPG, di 14:0 PG) using neutron spin echo spectroscopy throughout its anomalous phase transition that occurs over a 12 °C–20° C wide temperature window. Our results reveal that the membranes are softer and more dynamic during the phase transition than at higher temperatures corresponding to the fluid phase and provide direct experimental evidence for the predicted increase in membrane fluctuations during lipid melting. These results provide new insights into the nanoscale lipid membrane dynamics during the melting transition and demonstrate how these dynamics are coupled to changes in the membrane structure.

Highlights

Phospholipids undergo a main melting transition (Tm) associated with a change in the lipid physical state from an ordered phase at low temperatures to a disordered and fluid phase at high temperatures
We study the collective dynamics of dimyristoylphosphatidylglycerol (DMPG, di 14:0 PG) using neutron spin echo spectroscopy throughout its anomalous phase transition that occurs over a 12 C–20 C wide temperature window
Our results reveal that the membranes are softer and more dynamic during the phase transition than at higher temperatures corresponding to the fluid phase and provide direct experimental evidence for the predicted increase in membrane fluctuations during lipid melting

Summary

Introduction

Phospholipids undergo a main melting transition (Tm) associated with a change in the lipid physical state from an ordered phase at low temperatures to a disordered and fluid phase at high temperatures. Dimyristoylphosphatidylglycerol (DMPG, diC 14:0 PG) is especially well-studied because the melting transition spans over a 20 C wide temperature window at low buffer ionic strengths and lipid concentrations and sharpens with increasing lipid and/or salt concentration in the buffer What makes this transition even more unusual is that it is associated with macroscopic changes in the lipid solution properties including the solution turbidity, viscosity, and conductivity.[3,4,5]

Methods

Discussion

Conclusion