Conformational disorder in unsaturated phospholipids by FTIR spectroscopy

Area of Science:

• Biophysics
• Spectroscopy
• Materials Science

Background:

• Phospholipids exhibit various conformational states influencing membrane properties.
• Understanding conformational disorder is crucial for lipid phase behavior.
• FTIR spectroscopy is a powerful tool for probing molecular conformations.

Purpose of the Study:

• To monitor conformational disorder in liquid alkenes and phospholipid phases (L alpha and Hparallel).
• To analyze the impact of unsaturated fatty acid chains on lipid conformational states.
• To investigate changes in conformer distributions during the L alpha to Hparallel phase transition.

Main Methods:

• Utilized Fourier Transform Infrared (FTIR) spectroscopy to analyze molecular vibrations.
• Focused on the CH2 wagging region (1330-1390 cm-1) for conformational analysis.
• Semi-quantitatively estimated changes in conformer populations during phase transitions.

Main Results:

• Identified distinct FTIR bands associated with specific conformational states (end-gauche, double gauche, kink, gtg).
• Observed increased conformational disorder in unsaturated phosphatidylcholines (PCs) compared to phosphatidylethanolamines (PEs).
• Documented changes in conformer populations during the L alpha to Hparallel transition for various PE derivatives.

Conclusions:

• FTIR spectroscopy effectively differentiates conformational states in saturated and unsaturated lipid chains.
• Unsaturated phospholipids exhibit varying degrees of disorder depending on headgroup and fatty acid composition.
• The L alpha to Hparallel transition involves subtle increases in specific conformational states, consistent with calorimetric data.