Single Lipid Bilayers Constructed on Polymer Cushion Studied by Sum Frequency Generation Vibrational Spectroscopy

Area of Science:

• Biophysics
• Materials Science
• Surface Chemistry

Background:

• Planar lipid bilayers on inorganic substrates are common cell membrane models.
• Substrate-lipid interactions can affect model accuracy.
• Soft polymer cushions can mitigate these interactions.

Purpose of the Study:

• To evaluate a poly (L-lactic acid) (PLLA) polymer cushion as a substrate for single lipid bilayers.
• To compare lipid bilayer structure and peptide interactions on PLLA versus a traditional CaF(2) surface.
• To establish a more accurate cell membrane model for studying transmembrane proteins.

Main Methods:

• Sum frequency generation (SFG) vibrational spectroscopy.
• Assembly of asymmetric lipid bilayers (DPPG/d-DPPG) on CaF(2) and PLLA substrates.
• Investigation of antimicrobial peptide (Cecropin P(1)) interactions with lipid bilayers.

Main Results:

• Lipid bilayers on CaF(2) and PLLA substrates exhibited similar structures.
• Interactions between the antimicrobial peptide Cecropin P(1) and lipid bilayers were comparable on both surfaces.
• The PLLA cushion effectively prevented direct substrate-lipid interactions.

Conclusions:

• The hydrophilic PLLA cushion is a suitable substrate for supporting single lipid bilayers.
• The PLLA-supported lipid bilayer system serves as a robust cell membrane model.
• This model minimizes substrate artifacts, crucial for studying transmembrane protein structure and function.