Metal Complex Lipids for Fluid-Fluid Phase Separation in Coassembled Phospholipid Membranes

Area of Science:

• Biochemistry
• Materials Science
• Membrane Biophysics

Background:

• Lipid membranes exhibit complex phase behaviors crucial for biological functions.
• Controlling lipid organization within fluid membranes remains a challenge.
• Metal complex lipids offer novel functionalities for membrane manipulation.

Purpose of the Study:

• To investigate the effect of a specific metal complex lipid, [Mn(L1)], on the phase behavior of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes.
• To explore the potential of metal complex lipids in inducing and controlling fluid-fluid phase separation.
• To determine the stability of these phase-separated domains at physiological temperatures.

Main Methods:

• Synthesis and characterization of the metal complex lipid [Mn(L1)].
• Preparation of giant unilamellar vesicles (GUVs) composed of DMPC and varying concentrations of [Mn(L1)].
• Variable temperature fluorescence microscopy to observe phase separation and domain formation in GUVs.

Main Results:

• A small addition of [Mn(L1)] induced clear fluid-fluid phase separation in DMPC membranes.
• The phase transition temperatures (T_c) of the lipid domains were lower than that of pristine DMPC.
• Phase-separated domains remained visible in the fluid phase up to 37°C, exceeding the T_c of DMPC.

Conclusions:

• Metal complex lipids can effectively induce and stabilize fluid-fluid phase separation in lipid bilayers.
• This phenomenon allows for the control of lipid distribution within fluid membranes.
• Metal complex lipids present a novel strategy for modulating membrane properties and functions.