Holmium complex with phospholipids as ¹H NMR temperature probe for membrane systems

Area of Science:

• Biophysical Chemistry
• Lipid Bilayer Dynamics
• Lanthanide Probes

Background:

• Lanthanide ions are valuable probes for studying lipid membrane structure and dynamics.
• Understanding temperature effects on lanthanide-induced chemical shifts (LISs) is crucial for interpreting membrane phase behavior.
• Previous studies established anti-Curie dependence in POPC-Pr systems.

Purpose of the Study:

• To investigate the temperature dependence of LISs in different phospholipid-lanthanide systems.
• To correlate observed LIS temperature dependencies with lipid phase transitions.
• To compare Ho-based systems with previously studied Pr-based systems.

Main Methods:

• Preparation of unilamellar liposomes composed of POPC, DPPC, and DMPC.
• Incorporation of holmium (Ho) as a lanthanide probe.
• Measurement of temperature dependence of lanthanide-induced chemical shifts (LISs).

Main Results:

• POPC-Ho systems exhibited anti-Curie dependence of LISs, consistent with POPC-Pr findings.
• DPPC-Ho and DMPC-Ho systems showed unique temperature-dependent features.
• These features in DPPC- and DMPC-Ho systems are likely associated with lipid phase transitions.

Conclusions:

• Lanthanide probes provide insights into temperature-dependent behavior of different lipid bilayers.
• The observed LIS temperature dependence can differentiate between fluid (POPC) and gel/phase-transitioning (DPPC, DMPC) lipid phases.
• Ho-LISs offer a viable method for studying lipid-lanthanide interactions and membrane phase behavior.