Characterization of Parallel β-Sheets at Interfaces by Chiral Sum Frequency Generation Spectroscopy.

Area of Science:

• Biophysics
• Spectroscopy
• Computational Chemistry

Background:

• Protein secondary structure characterization at interfaces is limited by current surface-selective optical techniques.
• Understanding the orientation and behavior of protein aggregates at interfaces is crucial for biological and material science applications.

Purpose of the Study:

• To develop and apply a combined spectroscopic and computational approach for characterizing parallel beta-sheets at interfaces.
• To investigate the interfacial behavior of human islet amyloid polypeptide aggregates and a designed polypeptide.

Main Methods:

• Chiral sum frequency generation (SFG) spectroscopy was employed to probe interfacial structures.
• Computational modeling was used to analyze the spectroscopic data and understand molecular orientations.
• Studies were conducted at lipid/water and air/glass interfaces.

Main Results:

• Parallel beta-sheets exhibit distinct orientations depending on the interface.
• Characteristic chiroptical responses were observed in the amide I and N-H stretch regions.
• Theoretical analysis confirmed the link between chiroptical signals and beta-sheet symmetry, orientation, and vibrational coupling.

Conclusions:

• The combination of chiral SFG spectroscopy and computational modeling provides valuable insights into interfacial protein structures.
• This approach successfully characterizes the orientation and vibrational properties of parallel beta-sheets at different interfaces.
• The findings advance the understanding of protein aggregation and interfacial phenomena.