Temperature and time induced assembly phase changes of engineered spidroin protein solutions

Area of Science:

• Biomaterials Science
• Protein Engineering
• Materials Chemistry

Background:

• Silk-like protein materials display complex assembly behaviors.
• Understanding molecular origins of temperature and time-dependent phase response is crucial for material design.

Purpose of the Study:

• To investigate the molecular mechanisms behind the temperature and time-dependent assembly of silk-like protein materials.
• To elucidate the role of intrinsically disordered regions and folded domains in protein gelation.

Main Methods:

• Molecular dynamics simulations
• Circular Dichroism (CD) spectroscopy
• Fourier-Transform Infrared (FTIR) spectroscopy
• Optical microscopy

Main Results:

• Assembly phase response between 20-80°C is driven by strong interprotein interactions.
• Phase transitions are governed by entropy of glycine-rich regions and hydrophobic interactions of alanine-rich α-helices.
• Irreversible gelation observed at high temperatures (thermal gelation via β-sheet formation) and over time (time-induced gelation via percolation).

Conclusions:

• Identified time as a distinct design variable for silk-like protein gels, separate from molecular characteristics and solution conditions.
• Extracted assembly guidelines for controlling gel formation and properties.
• Demonstrated the interplay between protein structure, solution conditions, and macroscopic material behavior.