Nanoscale optical and structural characterisation of silk

Area of Science:

• Materials Science
• Biophysics
• Nanotechnology

Background:

• Silk's unique properties stem from its hierarchical structural anisotropy at the nanoscale.
• Understanding fibril composition, particularly β-sheets, is crucial for analyzing silk's structure-property relationships.

Purpose of the Study:

• To analyze the nanoscale composition of silk at the highest possible spatial resolution.
• To investigate the relationship between silk's nanoscale structure and its unique optical and mechanical properties.

Main Methods:

• High-resolution nanoscale optical and structural property measurements were performed on 100 nm thick longitudinal silk fiber slices.
• Hyperspectral mapping of absorbance and molecular orientation was conducted using synchrotron radiation at IR wavelengths (2-10 μm).
• Sub-wavelength optical resolution techniques were employed to achieve approximately 10 nm resolution.

Main Results:

• The study achieved the highest spatial resolution to date (ca. 10 nm) for analyzing silk's nanoscale structure.
• Reliable distinction of transmission changes as low as 1-2% was achieved, particularly for the anisotropy of amide bands.
• Detailed nanoscale optical and structural properties of silk fibrils and β-sheets were mapped.

Conclusions:

• The achieved high spatial resolution provides unprecedented insights into silk's hierarchical structure.
• The findings enhance our understanding of how nanoscale composition dictates silk's unique material properties.
• This methodology enables detailed analysis of molecular orientation and composition in biological materials at the nanoscale.