Sensitive Detection of Biomolecular Adsorption by a Low-Density Surfactant Layer Using Sum-Frequency Vibrational...

Area of Science:

• Biophysical Chemistry
• Surface Science
• Spectroscopy

Background:

• Biomembranes mediate molecular interactions crucial for biological processes.
• Understanding these interactions informs drug design and biomaterial development.

Purpose of the Study:

• To investigate the interaction between aromatic molecules and a choline-containing lipid (DPTAP) using sum-frequency vibrational spectroscopy.
• To probe the adsorption mechanism and quantify interaction strengths via cation-π interactions.

Main Methods:

• Sum-frequency vibrational spectroscopy (SFVS) was employed to monitor changes in the lipid monolayer.
• DPTAP monolayers were formed at the air/water interface.
• Aromatic molecules were introduced into the subphase to observe adsorption effects.

Main Results:

• Laser heating caused spectral changes indicating a bare air/water interface.
• Aromatic molecule introduction induced signal reappearance, signifying adsorption to DPTAP.
• Cation-π interactions were identified as the driving force for adsorption.
• Relative interaction strengths of various aromatic molecules were determined.
• Zwitterionic DPPC showed weaker interaction than cationic DPTAP.

Conclusions:

• SFVS is effective for studying molecular adsorption at lipid interfaces.
• Cation-π interactions play a significant role in the binding of aromatic molecules to choline headgroups.
• The method allows for quantitative comparison of binding affinities.