Internal Secondary Structural Conformational States of Silk Fibroin Studied by Raman Spectroscopy with Band...

Area of Science:

• Materials Science
• Biomaterials Engineering
• Spectroscopy

Background:

• Silk fibroin (SF) is a versatile biomaterial with excellent mechanical properties.
• Understanding the structure-property relationship of SF under mechanical stress is crucial for its applications.
• The internal structural changes of SF during deformation are not fully elucidated.

Purpose of the Study:

• To investigate the response of silk fibroin's secondary structures to external tensile loads.
• To elucidate the deformation mechanism of silk fibroin at a molecular level.
• To highlight the role of the amide III band in SF's mechanical behavior.

Main Methods:

• Utilized polarized Raman spectroscopy to analyze SF's secondary structures.
• Performed tensile loading-unloading experiments.
• Analyzed characteristic spectral bands, focusing on the amide III band variations.

Main Results:

• Observed significant variations in the amide III band, especially the 1210 cm^-1 random coil subpeak, under tensile stress.
• Hysteresis loops in loading-unloading experiments indicated irreversible structural changes.
• Demonstrated the transition of random coils to β-sheets within the SF network upon tensile elongation.

Conclusions:

• Tensile strain induces a structural transformation from random coils to β-sheets in silk fibroin.
• This molecular rearrangement contributes to the observed stiffening behavior of SF fibers.
• The amide III band is a critical indicator for understanding SF's mechanical deformation.