Structural differences between native Hen egg white lysozyme and its fibrils under different environmental conditions

Area of Science:

• Biochemistry
• Protein Chemistry
• Spectroscopy

Background:

• Native hen egg white lysozyme (HEWL) can form fibrils under specific conditions.
• Protein fibrillation is influenced by environmental factors like pH and ion presence.
• Understanding structural changes during fibrillation is crucial for disease research.

Purpose of the Study:

• To investigate the structural differences between native HEWL and its fibrils.
• To analyze the impact of pH (7.4 vs. 10.7) and Cu(II) ions on HEWL fibril structure.
• To quantify structural variations using Raman spectroscopy and principal component analysis.

Main Methods:

• Raman spectroscopy was employed to collect spectral data from native HEWL and its fibrils.
• Principal Component Analysis (PCA) was used to analyze spectral variations.
• Overlap areas of PCA scores quantified structural differences between species and conditions.
• Standard deviations of PCA scores assessed intra-species structural variability.

Main Results:

• Significant molecular structure differences were observed between HEWL fibrils grown at pH 7.4 and pH 10.7.
• The presence of Cu(II) ions led to similar molecular structures in HEWL fibrils across both pH conditions.
• PCA revealed distinct spectral variations within each HEWL species, indicating structural heterogeneity.

Conclusions:

• Environmental pH critically dictates HEWL fibril molecular structure.
• Cu(II) ions can mitigate pH-induced structural divergence in HEWL fibrils.
• Raman spectroscopy coupled with PCA provides a robust method for characterizing protein structural dynamics and variability.