Intramolecular hydrogen bonding in cardiolipin

Area of Science:

• Biochemistry
• Spectroscopy
• Membrane Biophysics

Background:

• Cardiolipin (CL) is a key phospholipid in mitochondrial membranes.
• Proton conduction across membranes is crucial for cellular energy production.
• Understanding CL's molecular structure is vital for elucidating its function.

Purpose of the Study:

• To investigate intramolecular hydrogen bonding in beef heart cardiolipin (18:0-CL) and its synthetic deoxy analogue (16:0-dCL).
• To determine if hydrogen bonding provides a structural basis for proton conduction at the molecular level.

Main Methods:

• Fourier transform infrared (FT-IR) spectroscopy was employed.
• Experiments were conducted on aqueous dispersions, dry films, and CCl4 solutions.
• Differential scanning calorimetry (DSC) was used to determine phase transition temperatures (Tm).

Main Results:

• Evidence suggests intramolecular C-OH...PO2- hydrogen bonding in 18:0-CL, particularly in dry films and CCl4 solutions.
• This bonding was absent in the 16:0-dCL analogue, indicating the importance of the central C-OH group.
• A significant increase in Tm upon switching from H2O to D2O in aqueous dispersions of 18:0-CL supports C-OH hydrogen bonding.

Conclusions:

• The central C-OH group in 18:0-CL plays a role in forming intramolecular hydrogen bonds with phosphate groups.
• These hydrogen bonds offer a potential structural basis for proton conduction in cardiolipin molecules.
• The findings contribute to understanding cardiolipin's role in membrane function and proton transport.