A Solid Phase Vibrational Circular Dichroism Study of Polypeptide-Surfactant Interaction.

Area of Science:

• Biophysical Chemistry
• Spectroscopy
• Polymer Science

Background:

• Understanding interactions between charged polymers and surfactants is crucial for materials science and drug delivery.
• Vibrational Circular Dichroism (VCD) spectroscopy is a powerful tool for studying molecular structure and chirality.
• Previous studies have explored polypeptide-surfactant interactions, but direct observation of chirality transfer in specific spectral regions remained challenging.

Purpose of the Study:

• To investigate the interaction between poly-l-lysine (PLL) and poly-l-arginine (PLAG) with sodium dodecyl sulfate (SDS).
• To examine the interaction between poly-l-glutamic acid (PLGA) and poly-l-aspartic acid (PLAA) with tetradecyltrimethylammonium bromide (TTAB).
• To explore the potential for chirality transfer from polypeptides to achiral surfactants using VCD spectroscopy.

Main Methods:

• Vibrational Circular Dichroism (VCD) spectroscopy was employed in the C-H stretching and Amide I regions.
• Measurements were performed on samples in both solution and mull states.
• A specialized sample preparation technique involving lyophilization and mull preparation was utilized to overcome measurement limitations.

Main Results:

• Chirality transfer from polypeptides to achiral surfactants was observed in the C-H stretching region, a feat not possible in solution.
• The sample preparation technique proved effective for VCD measurements, revealing new interaction details.
• SDS induced a secondary structure change in PLL to β-sheet and in PLAG to α-helix; TTAB disrupted PLGA and PLAA structures. These findings were corroborated by electronic circular dichroism and solution VCD spectra.

Conclusions:

• The study successfully demonstrated chirality transfer from polypeptides to surfactants, particularly evident in the C-H stretching region via specialized sample preparation.
• The observed structural changes highlight the significant impact of surfactants on polypeptide secondary structures.
• The findings underscore the utility of VCD spectroscopy with advanced sample preparation for elucidating complex biomolecular interactions.